Embed Size (px)
Citation preview
Par
is 2
00
9
XL
VII
th E
HP
RG
Co
nfe
ren
ce
Conference Booklet
A. Polian M. Gauthier
S. Klotz
2
3
Introduction
The XLVIIth meeting of the European High Pressure Research Group will be held from the 6th – 11th of September, 2009 in Paris.
The EHPRG is a multidisciplinary organization, and its meetings have to reflect this broad scientific interest from biosciences to chemistry, geosciences, materials sciences, with a special emphasis on technical and theoretical advances.
When this introduction was written we had received 300 papers. This was astonishing for us because of the AIRAPT meeting organized in July. It proves the vitality of the European sciences using high pressure as a tool. We have tried to avoid as much as
possible the conflicting choice between simultaneous presentations and kept the number of parallel sessions as low as possible.
A special session "Partnership for Extreme Condition Science at ILL/ESRF in Grenoble" is organized on the last day. The purpose of this session is to discuss the set up of a high pressure support facility in Grenoble, shared between the “Insitut Laue Langevin” (ILL) and the European Synchrotron Radiation Facility (ESRF). Everyone's contribution is welcome.
We have also planned a free pre-conference European school. Its aim is to help young participants to become acquainted with the multidisciplinary aspect of the meeting. It is supported by the "Réseau Technologique de Recherches Avancées en Hautes Pressions" of the CNRS and chaired by Y. Le Godec.
The organization of this conference has only been made possible thanks to a strong support from French institutions. We would like to thank the French « Ministère de l'Enseignement Supérieur et de la Recherche », the “Région Ile de France”, the city of Paris, and obviously, the « Centre National de la Recherche Scientifique » (CNRS), the « Université Pierre et Marie Curie - Paris VI » and the “Institut de Minéralogie et de Physique des Milieux Condensés”. We are also pleased to mention the support we have received from several industrial companies. These contributions allowed us to practice a low fees policy and support many young talented scientists to come to Paris.
The sessions will take place in a former convent, "Les Cordeliers" that now belongs to the Université Pierre et Marie Curie. It is situated in the heart of "Quartier Latin", the historical university area of Paris, at walking distance from many historical and cultural sites of Paris. We hope this will make this an enjoyable meeting of high scientific quality.
A. Polian - M. Gauthier - S. Klotz
4
5
Contents
Introduction _______________________________________________________________ 3
Committees _______________________________________________________________ 7
Social Program ___________________________________________________________ 11
Tourism in Paris ___________________________________________________ 11
Visit to Versailles __________________________________________________ 12
Conference Diner __________________________________________________ 13 Site Map _________________________________________________________________ 15
Conference schedule _______________________________________________________ 17
Abstracts ________________________________________________________________ 29
Plenary lectures ___________________________________________________ 31
Theory ___________________________________________________________ 39
Food Sciences _____________________________________________________ 63
Biosciences _______________________________________________________ 97
Advances in Laboratory Techniques __________________________________ 115
Advances in Large Facilities Techniques _______________________________ 139
Geosciences______________________________________________________ 165
Molecular Systems ________________________________________________ 187
Nanosciences ____________________________________________________ 205
Simple systems and metals _________________________________________ 227
Semiconductor properties __________________________________________ 237
Magnetic and Electronic Properties __________________________________ 267
Solvothermal Processes ____________________________________________ 319
Chemistry _______________________________________________________ 329
Synthesis ________________________________________________________ 345 Author Index ____________________________________________________________ 367
Preconference School _____________________________________________________ 377
Sponsors ________________________________________________________________ 379
6
7
Committees
International Advisory Committee
Rajeev Ahuja Uppsala Sweden
Reinhard Boehler Mainz Germany
Vadim Brazhkin Troitsk Russia
Peter Butz Karlsruhe Germany
Gérard Demazeau Bordeaux France
Leonid Dubrovinsky Bayreuth Germany
Eliane Dumay Montpellier France
Valentin Garcia Baonza Madrid Spain
Jean-Pierre Gaspard Liège Belgium
Didier Jaccard Genève Switzerland
Jiri Kamarad Prague Czech Republic
Andrzej Katrusiak Poznan Poland
Gerasimos Kourouklis Thessaloniki Greece
Paul Loubeyre Bruyères le Châtel France
Paul McMillan London UK
Richard Nelmes Edinburgh UK
Moshe Pasternak Tel Aviv Israel
Renato Pucci Catania Italy
Bruno Reynard Lyon France
Alfredo Segura Valencia Spain
Laszlo Smeller Budapest Hungary
Karl Syassen Stuttgart Germany
8
EHPRG Committee
R. Winter University of Dortmund Germany
Chairman
G. G. N. Angilella University of Catania Italy
Secretary
K. V. Kamenev University of Edinburgh UK
Treasurer
O. Andersson Umeå University, Umeå Sweden
J. A. Alonso Instituto de Ciencia de Materiales, Madrid Spain
E. Boldyreva Novosibirsk State University Russia
F. Datchi Université Pierre et Marie Curie, Paris France
L. S. Dubrovinsky Bayerisches Geoinstitut, Bayreuth Germany
D. Dunstan Queen Mary University, London UK
V. García-Baonza Universidad Complutense de Madrid, Madrid Spain
M. Hanfland ESRF, Grenoble France
A. Katrusiak Adam Mickiewicz University, Poznan Poland
G. Laurenczy Université de Lausanne Switzerland
P. Postorino Università di Roma La Sapienza, Roma Italy
A. San Miguel Université Lyon 1, Lyon France
L. Smeller Semmelweis University, Budapest Hungary
A. Soldatov Luleå Technical University Sweden
K. Syassen Max-Planck-Institut, Stuttgart Germany
S. Ves Aristotle University of Thessaloniki Greece
Ex-officio members:
R. Boehler Max-Planck Institut für Chemie, Mainz Germany
President of the AIRAPT
E. P. O'Reilly Tyndall National Institute (NMRC), Cork Ireland
Chairman of the Condensed Matter Division
of the European Physical Society
9
Organizing Committee
A. Polian IMPMC, Paris Chairman
M. Gauthier IMPMC, Paris Co-Chairman
S. Klotz IMPMC, Paris Co-Chairman
Y. Le Godec IMPMC, Paris School Chairman
G. Fiquet IMPMC, Paris
J.P. Itié SOLEIL, St Aubin
Chairpersons
G. G. N. Angilella University of Catania, Catania Italy
R. Bini LENS, Firenze Italy
R. Boehler Max-Planck Institut für Chemie, Mainz Germany
G. Demazeau Université de Bordeaux France
L. Dubrovinsky Bayerisches Geoinstitut, Bayreuth Germany
E. Dumay Université Montpellier 2, Montpellier France
M. Eremets Max-Planck-Institut für Chemie, Mainz Germany
G. Fiquet Université P&M Curie, Paris France
V. Garcia Baonza Universidad Complutense de Madrid Spain
M. Hanfland ESRF, Grenoble France
M. Houska Food Research Institute, Prague Czech Republic
J. Kamarad Institute of Physics, Prague Czech Republic
A. Katrusiak Adam Mickiewicz University, Poznao Poland
P. Loubeyre CEA, Bruyères le Châtel France
P. McMillan University College London, London UK
R.J. Nelmes University of Edinburgh, Edinburgh UK
M.P. Pasternak Tel Aviv University, Tel Aviv Israel
R. Pucci University of Catania, Catania Italy
G. Rozenberg Tel Aviv University, Tel Aviv Israel
A.M. Saitta Université P&M Curie, Paris France
A. San Miguel Université Lyon 1, Lyon France
L. Smeller Semmelweis University, Budapest Hungary
K. Syassen Max-Planck-Institute Stuttgart Germany
R. Winter University of Dortmund Germany
P.Y. Yu University of California, Berkeley USA
10
11
Social Program
Tourism in Paris
Using Vélib'
Vélib’ is a Self Service “bike hire” system available 24 hours a day, 7 days a week.
Multi pick up and drop off location allows you to pick up your bike from one service point and drop off to another.
Don’t forget to observe the Highway Code and abide by the rules of safe cycling. Always remember to be considerate and be on the look out for other road users. Good to know! Your domestic multi-risk insurance policy may cover risks associated with civil liability during a bike trip*.
* Please check with your policy to ensure appropriate coverage.
Visit to Fragonard Perfume Museum
The perfume museum, which opened in 1983, occupies a very lovely Napoleon III town house built in 1860 by Lesoufaché, a student of Garnier. The decoration is entirely of that period.
Here you can discover a wonderful collection of perfumery objects that take you traveling through the ages.
Fragonard will be delighted to welcome you for a guided tour of this prestigious museum just a few steps from the Opéra Garnier.
Le musée du parfum
9 rue Scribe
75009 PARIS
Access:
RER A station Auber
Subway (3, 7, 8) “Opéra”
12
Visit to Versailles
On Wednesday 6th afternoon you will have the opportunity to visit one of the most famous french royal castle: Versailles.
Buses pick you at 14h (2 pm) at the conference site for an half an hour trip to Versailles.
During 3 hours, you can discover both the castle and the gardens.
You will be back in Paris at 18h (6 pm).
13
Conference Diner
Dinner will take place on board while cruising on the Seine.
Boarding will be opened at 19h30.
The boarding area “Quai de Bercy” is closed to the POPB, the “Parc de Bercy” and opposite to the “Bibliothèque Nationale de France: François Mitterrand”.
Access are summarized on the map
Bus stops “Terroirs de France” N° 24 or “Lacambeaudie” N° 62 Subway stops “Bercy” N°6 or “Cour Saint-Emilion” N°14 Car Park “Bercy St Emilion” 6 rue des pirogues de Bercy (Paris 12ème)
14
The conference site (the red mark) is situated in the “Quartier Latin”, the heart of the historical university area of the city. Lot of worth seeing sites are at a walking distance.
15
Site Map
Location of the conference center
15 rue de l’école de médecine
75006 Paris
Main Access
Bus stop “St Germain- Odéon” on lines 63, 86, 87, 96 for the closest.
Many other lines are in the nearby (21, 27, 38, 85, 58, 70)
Subway stop “Odéon” on both line N°4 and line N° 10
RER stop “Saint Michel” on both RER B and RER C
16
A « Porche » : Main Entrance – Reception-Registration
B Administration
C Cloître : Poster Sessions
S0 « Salle Marie Curie » : Exhibits-Poster Sessions
S1 « Amphi Faraboeuf »
S2 « Amphi Bilsky Pasquier »
S3 « Salle des Thèses »
S1 S0
A
B C
S2
S3
17
Conference schedule
Fara
boeu
fPa
squi
erTh
èses
Fara
boeu
fPa
squi
erFa
rabo
euf
Pasq
uier
Fara
boeu
fPa
squi
erTh
èses
Fara
boeu
fPa
squi
erFa
rabo
euf
Pasq
uier
Fara
boeu
fPa
squi
er
Fara
boeu
fPa
squi
erFa
rabo
euf
Pasq
uier
Fara
boeu
fPa
squi
er
Cloî
tre
18:0
0
Ban
quet
19h
30 -
24h
Soci
al P
rogr
amm
e
Vis
it t
o V
ersa
illes
14:0
014
:00
14:3
014
:30
13:3
013
:30
16:0
016
:00
Coff
ee b
reak
Theo
ryFo
od
Sci
ence
sG
eosc
ien
ces
Mag
net
ic a
nd
elec
tro
nic
pro
per
ties
Nan
osc
ien
ces
15:0
015
:00
Coff
ee b
reak
Coff
ee b
reak
15:3
015
:30
Theo
ryFo
od
Sci
ence
s
Cloî
tre
Po
ster
s
Theo
ry
Foo
d Sc
ien
ces,
Bio
scie
nce
s
Po
ster
s
Lab
Tech
, Lar
ge F
acili
ties
Tec
h
Geo
sc, M
ole
cula
r Sy
s, N
ano
sc
Cloî
tre
Po
ster
s
Sem
iCo
nd, M
agn
& E
lec,
Sim
ple
Sys
Synt
hesi
s, C
hem
istr
y, S
olv
o P
roc
Cloî
tre
16:3
016
:30
17:0
017
:00
Geo
scie
nce
s
Mag
net
ic a
nd
elec
tro
nic
pro
per
ties
Mag
net
ic a
nd
elec
tro
nic
pro
per
ties
17:3
017
:30
18:0
0
11:3
011
:30
12:0
012
:00
Lunc
h
Lunc
h
12:3
012
:30
13:0
013
:00
Lunc
h
Lunc
h
Ad
van
ces
in
Larg
e Fa
cilit
ies
Tech
niq
ues
Mo
lecu
lar
syst
ems
Syn
thes
isSi
mp
le s
yste
ms
Met
als
Plen
ary
Lect
ure
Ch
ris
Pic
kard
Fara
boeu
f
Ad
van
ces
in
Lab
ora
tory
Tech
niq
ues
Op
enin
g Se
ssio
n
Fara
boeu
f
Ad
van
ces
in
Larg
e Fa
cilit
ies
Tech
niq
ues
Fara
boeu
f
Plen
ary
Lect
ure
Pat
rick
Co
rdie
r
10:0
010
:00
Coff
ee b
reak
Coff
ee b
reak
Coff
ee b
reak
Coff
ee b
reak
10:3
010
:30
11:0
011
:00
XL
VII
th E
HP
RG
PA
RIS
6 -
11
Sep
tem
ber
20
09
Sun
day
Sep
tem
ber
6
Mo
nd
ay
Sep
tem
ber
7
Tues
day
Sep
tem
ber
8
Wed
nes
day
Sep
tem
ber
9
Thu
rsd
ay
Sep
tem
ber
10
Frid
ay
Sep
tem
ber
11
8:30
8:30
Reg
istr
atio
n9:
009:
00
9:30
9:30
Spec
ial S
essi
on
Dis
cuss
ion
of
a Pa
rtne
rshi
p
for
Extr
eme
Co
ndit
ions
Sci
ence
at
ILL/
ESR
F in
Gre
no
ble
Clo
sin
g Se
ssio
n
Fara
boeu
f
Plen
ary
Lect
ure
Ru
di V
oge
l
Fara
boeu
fFa
rabo
euf
Plen
ary
Lect
ure
Hu
ber
t H
up
per
tz
Reg
istr
atio
n
Wel
com
e P
arty
Solv
oth
erm
al
Pro
cess
es
Ch
emis
try
Bio
scie
nce
s
Bio
scie
nce
s
Fara
boeu
f
EHP
RG
AW
AR
D
EHP
RG
Gen
era
l Ass
emb
ly
Fara
boeu
f
Sem
ico
nd
uct
ors
Pro
per
ties
Sem
ico
nd
uct
ors
Pro
per
ties
Fara
boeu
f
Porc
he
18
19
Sunday September 6th
- 16h30 Welcome and Registration opening (Porche) - 17h - 18h EHPRG Committee Meeting (Curie) - 18h Get together party (Cloître)
20
Monday September 7th
- 8h30 Registration (Porche)
Opening session (Faraboeuf)
- 10h - 11h Welcome A. Polian
Plenary Lecture (Faraboeuf, Chairperson: G. G. N. Angilella)
- 11h - 12h Ab initio random structure searching - exploring high pressure with random numbers. C. J. Pickard
Lunch 12h-13h30
Theory (Faraboeuf, Chairperson: R. Pucci)
- 13h30 - 14h Invited Lecture Boron under high pressure: a first-principles study. S. I. Simak et al.
- 14h - 14h20 Superconductivity in BaSi2, Be2Li and other alloys under Pressure. A. Bergara et al.
- 14h20 - 14h40 Dynamical properties of tetragonal TbPO4 under pressure from ab initio calculations. J. Lopez-Solano et al.
- 14h40 - 15h Prediction and determination of the structural parameters of incommensurate crystal structure in Ca and Sc at high pressure. R. Ahuja et al.
Food Sciences (Pasquier, Chairperson: M. Houska)
- 13h30 - 14h Invited Lecture Association, dissociation and interactions of milk proteins under pressure. A. Kelly et al.
- 14h - 14h20 Pasting properties of high pressure treated starch suspensions. H. Simonin et al.
- 14h20 - 14h40 Influence of high pressure and elevated temperature on bacterial spores- inactivation mechanisms above 500 MPa. K. Reineke et al.
- 14h40 - 15h In-situ investigation of the turbulent-laminar transition of temperature fluctuation during the pressure building up to 300 MPa. K. Song et al.
Coffee break 15h-15h30
21
Theory (Faraboeuf, Chairperson: M. Saitta)
- 15h30 - 16h Invited Lecture Distortions and low symmetry environments in liquid metals: Na and Li at high pressure. J.Y. Raty et al.
- 16h - 16h20 A simple tight-binding model for the study of the melting properties of 4d transition metals under extreme conditions. C. Cazorla et al.
- 16h20 - 16h40 First principles studies of icosahedral boron carbides under extreme conditions. E. Betranhandy et al.
- 16h40 - 17h00 Elastic properties of iron under pressure: a first-principles study. O. Yu. Vekilova et al.
Food Sciences (Pasquier, Chairperson: E. Dumay)
- 15h30 - 16h Invited Lecture Rheological properties of biomatter at high pressure - measurement techniques and relevance for high pressure processes. L. Kulisiewicz et al.
- 16h - 16h20 IgE binding of apple allergens preserved after treatments at high pressure. A. Fernandez et al.
- 16h20 - 16h40 Influence of high pressure treatment on allergenicity of rDau c1 and carrot juice demonstrated by in vitro and in vivo tests. M. Heroldova et al.
- 16h40 - 17h00 Textural properties of fresh cheese made from milk treated by ultra-high pressure homogenisation. A. Zamora et al.
Poster Session 17h - 18h30 (Cloître)
Theory
Food Sciences
Biosciences
22
Tuesday September 8th
Plenary Lecture (Faraboeuf, Chairperson: R. Boehler)
- 9h - 10h Plastic deformation of minerals under high pressures: an experimental and theoretical challenge. P. Cordier
Coffee break 10h-10h30
Advances in Laboratory Technics (Faraboeuf, Chairperson: M. Eremets)
- 10h30 - 11h Invited Lecture Determination of thermal conductivity of materials in laser-heated DAC. P. Lazor et al.
- 11h - 11h20 Ruby microcrystal as a stress sensor. K. Takemura - 11h20 - 11h40 New measurements on helium at high pressure. P. Loubeyre et
al. - 11h40 - 12h Laser ultrasonics in diamond anvil cell (LU-DAC) technique for
elastic properties measurements at high pressures. N. Chigarev et al.
Molecular Systems (Pasquier, Chairperson: R. Bini)
- 10h30 - 11h Invited Lecture Ab initio simulation of simple molecular systems at extreme conditions. S. Scandolo
- 11h - 11h20 Structure of molecular CO2 at high pressures and temperatures. F. Datchi et al.
- 11h20 - 11h40 High pressure formation and characterization of a previously unobserved structure of clathrate hydrate. C. Tulk et al.
- 11h40 - 12h Salty ice VII under pressure. L.E. Bove et al.
Lunch 12h-13h30
Geosciences (Faraboeuf, Chairperson: G. Fiquet)
- 13h30 - 14h Invited Lecture Indoor vs Outdoor Geophysics. R. Liebermann - 14h - 14h20 Sound velocity measurements on Fe0.89Ni0.04Si0.07 to 108 GPa:
mineral physics constraints on the silicon abundance in the Earth’s core. D. Antonangelli et al.
- 14h20 - 14h40 Compressibility change in molten Fe and models of core formation. C. Sanloup et al.
- 14h40 - 15h Mass-Radius relations for low-mass exoplanets comparing different equations of state. F. Wagner et al.
Nanosciences (Pasquier, Chairperson: A. San Miguel)
- 13h30 - 14h Invited Lecture Raman studies of nanotubes under high pressure. D. Dunstan et al.
23
- 14h - 14h20 Nanocrystals of ZnO formed by the hot isostatic pressure (HIP) method. J. Gonzalez et al.
- 14h20 - 14h40 Transport properties of individual carbon nanotubes under high pressure. C. Caillier et al.
- 14h40 - 15h00 Pressure-induced phenomena in single-walled carbon nanotubes probed by infrared spectroscopy. A. Abouelsayed et al.
Coffee break 15h-15h30
Geosciences (Faraboeuf, Chairperson: L. Dubrovinsky)
- 15h30 - 16h Invited Lecture Crystallization and melting of minerals in-situ at high pressure. V. Prakapenka et al.
- 16h - 16h20 Eutectic melting of lower mantle. D. Andrault et al. - 16h20 - 16h40 Ab initio molecular dynamics simulations of liquid fayalite
(Fe2SiO4) at high pressures. D. Muñoz Ramo et al. - 16h40 - 17h00 In situ viscosity measurements of liquid Fe-S alloys at high
pressures. K. Funakoshi et al.
Magnetic and Electronic Properties (Pasquier, Chairperson: J. Kamarad)
- 15h30 - 16h Invited Lecture Magnetism under pressure in some selected correlated electron systems. M. M. Abd-Elmeguid
- 16h - 16h20 Evidence for unusual magnetic order in cubic FeGe beyond its quantum phase transition. H. Wilhelm et al.
- 16h20 - 16h40 Magnetism of amorphous iron at pressures up to 35 GPa. M. Lerche et al.
- 16h40 - 17h00 Pressure influence on magnetism in ErCo2 and Er(Co0.975Si0.025)2 V. Sechovský et al.
Poster Session 17h - 18h30 (Cloître and Curie)
Advances in Laboratory Techniques
Advances in Large Facilities Techniques
Geosciences
Molecular Systems
Nanosciences
Simple Systems
24
Wednesday September 9th
Advances in Large Facilities Technics (Faraboeuf, Chairperson:M. Hanfland)
- 9h - 9h30 Invited Lecture The extreme conditions beamline at PETRA III, DESY: possibilities to conduct time resolved monochromatic and pink beam diffraction experiments in laser heated DAC. H.P. Liermann et al.
- 9h30 - 9h50 Melting in the diamond anvil cell using energy dispersive XAS. G. Aquilanti et al.
- 9h50 - 10h10 Time-of-Flight single-crystal neutron diffraction to 10 GPa. C. Bull et al.
- 10h10 - 10h30 Three dimensional X-ray diffraction study of MgGeO3 post-perovskite plastically deformed at 80 GPa. C. Nisr et al.
Solvothermal Processes (Pasquier, Chairperson: G. Demazeau)
- 9h - 9h30 Invited Lecture Solvothermal crystal growth: elaboration of ZnO single crystals. A. Largeteau et al
- 9h30 - 9h50 Re-crystallization and micronization of pharmaceutical compounds by applying the supercritical fluid technology. Y.P. Chen
- 9h50 - 10h10 Reaction of 2-Methoxyethanol in sub- and supercritical water. Y. Uosaki et al.
- 10h10 - 10h30 How CO2 induces asphaltene flocculation at high pressure: an experimental investigation. H. Carrier et al.
Biosciences (Salle des Thèses, Chairperson: R. Winter)
- 9h - 9h30 Invited Lecture Mechanical properties of amyloid fibrils from x-ray diffraction experiments in the diamond anvil cell. F. Meersman et al.
- 9h30 - 9h50 Non denaturating pressure effect on protein-water dynamics and structure. M.G. Ortore et al.
- 9h50 - 10h10 Structure-function study of tetrameric urate oxidase studied with fluorescent spectroscopy, SAXS and X-ray crystallography under high hydrostatic pressure. E. Girard et al.
- 10h10 - 10h30 Isothermal compressibility of macromolecular crystals and macromolecules: the case of Cu, Zn superoxide dismutase protein. I. Ascone et al.
Coffee break 10h30-11h
Advances in Large Facilities Technics (Faraboeuf, Chairperson: R. Nelmes)
- 11h - 11h30 Invited Lecture X-ray FEL applications in extreme states of matter research. T. Tschentscher
25
- 11h30 - 11h50 Application of charged particle beams of TWAC-ITEP accelerator for diagnostics of high dynamic pressure processes. S. Kolesnikov et al.
- 11h50 - 12h10 Current status of the high pressure neutron study at J-PARC. K. Komatsu et al.
- 12h10 - 12h30 Development of a new multi-purpose high pressure XRD, density and viscosity measurements setup at beamline ID27 of the ESRF. M. Mezouar et al.
Chemistry (Pasquier, Chairperson: A. Katrusiak)
- 11h - 11h30 Invited Lecture High-pressure asymmetric organic synthesis. J. Jurczak
- 11h30 - 11h50 High pressure hydrogen generation and delivery. G. Laurenczy - 11h50 - 12h10 Influence of high explosives initial density on the reaction zone
for steady-state detonation. A. Utkin et al. - 12h10 - 12h30 Molecular dynamics calculations of molecular volumes.
N. Weinberg et al.
Biosciences (Salle des Thèses, Chairperson: L. Smeller)
- 11h - 11h30 Invited Lecture Kinetic methods under high pressure are helpful for understanding protein reaction mechanisms. R. Lange et al.
- 11h30 - 11h50 The Kinetics and mechanisms of pressure-jump induced phase transitions of lyotropic lipid mesophases. C. Jeworrek et al.
- 11h50 - 12h10 Role of high pressure and various factors on the inactivation of pathogens in biological media. N. Rivalain et al.
- 12h10 - 12h30 Pressure effects on the morphology and migration of mammalian cells. J. Schroeder et al.
Lunch 12h30-13h30
Social Program
A visit to Versailles 14h-18h
Conference Banquet
Diner on board from 19h30 to 24h
26
Thursday September 10th
Plenary Lecture (Faraboeuf, Chairperson: L. Smeller)
- 9h - 10h Cellular and molecular high pressure responses in bacteria. R. Vogel
Coffee break 10h-10h30
EHPRG Award (Faraboeuf, Chairperson: R. Winter)
- 10h30 - 11h30 Pressure-induced phenomena in complex manganese and cobalt oxides: tuning of magnetic, charge, orbital ordering and spin states. D. Kozlenko
EHPRG General Assembly 11h30-12h30 (Faraboeuf, Chairperson:R.Winter)
Lunch 12h30-13h30
Semiconductors Properties (Faraboeuf, Chairperson: P. Y. Yu)
- 13h30 - 14h10 Invited Lecture Theoretical studies of some high pressure properties of semiconductors. M.L. Cohen
- 14h10 - 14h30 Initial structure memory of pressure-induced transformations in phase change memory alloy Ge2Sb2Te5. C. Levelut et al.
- 14h30 - 14h50 Pressure-induced phase transitions on amorphous covalent systems studied by a combination of XAS and XRD and Raman spectroscopy. F. Coppari et al.
- 14h50 - 15h10 Anomalous pressure behavior of the ZnSe Raman spectrum. B. A. Weinstein et al.
Magnetic and Electronic Properties (Pasquier, Chairperson: M. Pasternak)
- 13h30 - 13h50 Superconductivity at 40 K in FeSe under high pressure. S. Medvedev et al.
- 13h50 - 14h10 High pressure structural investigations of Fe-based superconductors. I. Efthimiopoulos et al.
- 14h10 - 14h30 Magnetic order in Tb2Sn2O7 under high pressure: from ordered spin ice to spin liquid and antiferromagnetic order. I. Mirebeau et al.
- 14h30 - 14h50 Magnetic and spectroscopic characterization of Ni3+ and Co3+ doped LaAlO3. Interplay between spin states and Jahn-Teller effect. M.N. Sanz-Ortiz et al.
- 14h50 - 15h10 Effect of high pressure on multiferroic BiFeO3. P. Bouvier et al.
Coffee break 15h-15h30
27
Semiconductors Properties (Faraboeuf, Chairperson: K. Syassen)
- 15h30 - 15h50 Elastic and visco-elastic measurements in diamond anvil cell. F. Decremps et al.
- 15h50 - 16h10 Photoluminescence of InP/GaP QDs under extreme conditions. M. Millot et al.
- 16h10 - 16h30 Electron-phonon coupling in semiconductors and their nanostructures: ab initio approach. J. Sjakste et al.
- 16h30 - 17h00 Invited Lecture A long day's journey in high pressure research. M. Cardona
Magnetic and Electronic Properties (Pasquier, Chairperson: G. Rozenberg)
- 15h30 - 15h50 Filling of the Mott-Hubbard gap in the oxyhalides TiOCl and TiOBr induced by external pressure. C. A. Kuntscher et al.
- 15h50 - 16h10 Evidence for a monoclinic metallic phase in high-pressure VO2. P. Postorino et al.
- 16h10 - 16h30 The Normal - Inverse spinel configuration crossover in magnetite. M.P. Pasternak et al.
- 16h30 - 17h00 Invited Lecture Transparent dense sodium. M. Eremets et al.
Poster Session 17h - 18h30 (Cloître and Curie)
Semiconductors Properties
Magnetic and Electronic Properties
Synthesis
Chemistry
Solvothermal Processes
28
Friday September 11th
Plenary Lecture (Faraboeuf, Chairperson: P. McMillan)
- 9h - 10h New trends in high pressure chemistry of materials. H. Huppertz
Coffee break 10h-10h30
Synthesis (Faraboeuf, Chairperson : V. Garcia Baonza)
- 10h30 - 11h Invited Lecture High-pressure synthesis of novel superhard phases in the B-C-N system. V. Solozhenko
- 11h - 11h20 Collapsed silicalite at high pressure: a novel form of topologically ordered amorphous silica. J. Haines et al.
- 11h20 - 11h40 From mixing to reactivity: Novel Ge0.9Sn0.1 solid solution formation at 10 GPa after heating. G. Serghiou et al.
- 11h40 - 12h Synthesis, structural and magnetic disordering in the IrSr2ReCu2O8+x family of metalo-cuprates by HP+HT oxidation. M.Á. Alario-Franco et al.
Simple Systems - Metals (Pasquier, Chairperson: P. Loubeyre)
- 10h30 - 11h Invited Lecture Metal to semiconductor transition in lithium above 80 GPa. T. Matsuoka et al.
- 11h - 11h20 Structural phase transitions of sodium nitride Na3N at high pressure. G. Vajenine et al.
- 11h20 - 11h40 High pressure experiments as a test of density functional theory. A. Dewaele et al.
- 11h40 - 12h Boron behavior at high pressure. L. Dubrovinsky et al.
Closing session 12h-13h (Faraboeuf, Chairperson: A. Polian)
Special Session 14h-18h (Faraboeuf, Chairperson: M. Mezouar, M. M. Koza)
Discussion of a partnership for extreme conditions science at ILL/ESRF in Grenoble
29
Abstracts
30
31
Plenary lectures
C.J. Pickard
Ab initio random structure searching - exploring high pressures with random
numbers__________________________________________________________ 33
P. Cordier
Plastic deformation of minerals under high pressures: an experimental and
theoretical challenge _______________________________________________ 34
R.F. Vogel
Cellular and molecular high pressure responses in bacteria _______________________ 35
H. Huppertz
New Trends in High Pressure Chemistry of Materials ____________________________ 36
EHPRG AWARD : D. Kozlenko
Pressure-induced phenomena in complex manganese and cobalt oxides: tuning
of magnetic, charge, orbital ordering and spin states. ____________________ 37
Special invited lectures on the occasion of Prof. M. Cardona's 75th birthday
M. L. Cohen
Theoretical studies of some high pressure properties of semiconductors ___________ 239
M. Cardona
A long day’s journey in high pressure research ________________________________ 246
32
33
Ab initio random structure searching - exploring high pressures with random numbers
Chris J. Pickard
Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT
It is an obvious goal for a complete theory of the solid state to be able to reliably predict the structures adopted by large collections of atoms under a variety of conditions, including high pressure. But until relatively recently it is one that has been largely unrealised, with the first useful first principles approaches emerging only in 2006.
I will present a strikingly simple and effective approach to the unbiased prediction of crystal structures. Ab initio random structure searching (AIRSS) is based on an initial uniform random sampling of the space of possible structures, followed by robust structural optimisation to the local enthalpy minimum of each initial structure under quantum mechanical (density functional theory) forces and stresses.[1] More complex structures can be discovered by a judicious application of constraints to the search space. It can also be used as tool for solving crystal structures that have resisted standard experimental techniques.
Applications include the phase III of hydrogen[2], ionic ammonia as ammonium amide[3] and lithium, an elemental electride.[4]
[1] C.J. Pickard and R.J. Needs, Phys. Rev. Lett. 2006, 97, 45504 [2] C.J. Pickard and R.J. Needs, Nature Physics 2007, 3, 473-476 [3] C.J. Pickard and R.J. Needs, Nature Materials 2008, 7, 775-779 [4] C.J. Pickard and R.J. Needs, Phys. Rev. Lett. 2009, 102, 146401
Email: [email protected]
Keywords: structure prediction, density functional theory, ammonia, lithium
34
Plastic deformation of minerals under high pressures: an experimental and theoretical challenge
Patrick Cordier
Laboratoire de Structure et Propriétés de l’Etat Solide UMR 8008 CNRS - Université Lille 1 59650 Villeneuve d’Ascq (FRANCE)
Ninety eight percent of the Earth’s volume is at temperature above 1000°C. Surface processes like plate tectonics, earthquakes or volcanism are the visible consequences of convection flow within the mantle by which our planet dissipates its internal heat. Mantle convection is the result of plastic flow under extreme conditions of the rocks and minerals constituting the mantle. The pressure range within the mantle is between 10 and 135 GPa and temperature (which is less well constrained) is probably in the range 1000-3000 K. Another important parameter is the strain rate which is estimated to be in the range 10
-12 - 10
-14 s
-1 whereas
stresses could be as low as 1-10 MPa.
Plastic deformation is a constant volume process and continuum mechanics usually assumes that the plastic response is governed by the deviatoric part of the stress tensor and that confining pressure plays no role. The first influence of pressure within the mantle is to induce phase transformations of the minerals that one can find at the surface of the Earth. The main phase of the mantle appears to be a magnesium silicate with the perovskite structure that is stable at pressures above 25 GPa only. This phase must be synthesized under pressure and can be quenched to ambient pressure. Some other phases can not be quenched and must be studied in situ. Pressures in the mantle can be so high that profound changes of the electronic structure are induced. From the mechanical properties point of view, this can be seen through the elastic properties. Very strong increase of the elastic constants is observed with increasing pressure. The structure and properties of lattice defects responsible for plastic flow are thus likely to be influenced by high pressures as well.
We will first review briefly the recent (and ongoing) efforts made to achieve plastic deformation under pressure. The challenges are manifold. Obtaining an independent control of pressure and deviatoric stress is one. Measuring in situ stress and strain is the other and impressive progress has been made recently in that direction. In parallel with this evolution, we have been working on a multiscale modeling approach of plastic deformation on a physical basis that can account for the influence of pressure. The first step is to model crystal defects (dislocations) in minerals (i.e. materials with a complex crystal chemistry) under pressure, and then to predict their mobility and interactions. Some examples on ongoing research performed in our group on important phases of the mantle will be presented.
Email: [email protected] Keywords: mantle convection; plastic deformation; dislocation; multiscale modeling
35
Cellular and molecular high pressure responses in bacteria
Rudi F. Vogel
Technische Universität München, Technische Mikrobiologie, 85350 Freising, Germany
Proteomic[1]
and transcriptomic[2]
approaches and genetic analyses of high pressure (HP) mutants revealed that high pressure is a powerful tool to investigate cellular processes far beyond the mere inactivation of bacteria. Two approaches can be separated for which different responses to high pressure are apparent. Organisms can be shocked by short (nearly) lethal pressure pulses (e.g.150-400 MPa) and their response is characterized upon recovery. Alternatively, bacteria can be grown under sublethal (comparably low) pressures (e.g. 20-150 MPa) for a prolonged time, sometimes resulting in adaptation and mutation. Primary thermodynamic targets present in the cell were identified to be the ribosome and the cellular membrane.
It appears that translation is stalled in vivo at pressures above 40 MPa. Ribosomes can be returned to functionality by trans-translation and peptide tagging mediated by tmRNA and the ClpX protease/chaperon system. Both systems are turned on as a specific reaction of high pressure stress. Overexpression of ssrA enables growth under high pressure by helping to maintain ribosomal function in Gram-positive bacteria (Lactobacillus sanfranciscensis).
Depending on pressure height, HP can induce lipid sorting as well as phase and thickness changes in biological membrane systems. As these lipid membrane systems contain ca. 50% proteins these play a crucial role in membrane behaviour and are also directly affected by HP. We have studied multiple drug transporters LmrA and HorA from Lactococcus lactis and Lactobacillus brevis
[3], respectively, as well ToxR, a membrane protein sensor from
Photobacterium profundum and Vibrio cholerae in in vitro and in vivo systems (proteoliposomes and recombinant reporter bacteria)
[4] under HP. These proteins require
dimerization in the phospholipid bilayer for their functionality, which was favored in the liquid crystalline lipid phase. Our data suggest for both investigated systems that the dimerization ability of membrane proteins under HHP conditions occurring in the deep sea and in technical processes of sublethal pressure treatment is basically defined by the nature of the transmembrane segment (TMS) involved in dimerization and modulated by membrane structure. Changes in its lipid bilayer environment are restricted to changes of the rigidity of the membrane and hydrophobic mismatch, while no pressure-induced phase transitions nor ribosomal impairment disturbing the in vivo measurements are observed below 50 MPa.
[1] S. Hörmann, C. Scheyhing, J. Behr, M. Pavlovic, M. Ehrmann, R. F. Vogel, Proteomics. 2006, 6, 1878-85
[2] M. Pavlovic, S. Hörmann, R. F. Vogel, M. Ehrmann, Arch. Microbiol. 2005, 184, 11-17. [3] K. Linke, N. Periasamy, M. Ehrmann, R. Winter, R. F. Vogel, Appl. Environ. Microbiol. 2008,
74, 7821-7823. [4] N. Periasamy, H. Teichert, K. Weise, R. F. Vogel, R. Winter, Biochim. Biophys. Acta. 2009,
1788, 390-401.
E-mail: [email protected] Keywords: high pressure, bacteria, membrane lipids, ribosome
36
New Trends in High Pressure Chemistry of Materials
Hubert Huppertz
Institute for General, Inorganic, and Theoretical Chemistry, University of Innsbruck, A–6020 Innsbruck, Austria
High-pressure investigations in borate chemistry are rare and have been mainly performed from a geological point of view. In the last decade, systematic high-pressure experiments up to maximum pressures of 16 GPa have been carried out in our group focusing on high-pressure solid state chemistry of borates using the multianvil technique
[1]. In the context of
these investigations into new rare-earth and transition metal oxoborates, several new high-pressure polymorphs of known compositions, e.g. –MB4O7 (M = Ca, Zn, Hg), χ–REBO3 (RE = Dy, Er), ν–DyBO3, γ–RE(BO2)3 (RE = La–Nd), δ–RE(BO2)3 (RE = La, Ce), and δ–BiB3O6
[2],
were discovered. These investigations led to fundamental insights into the structural behaviour of oxoborates under high-pressure conditions. Especially the coordination of the boron and rare-earth atoms were of special interest in our investigations. Next to the synthesis of new modifications, new compositions were realized in our group. For example, all attempts to produce rare-earth metal(III) oxoborates with the ratio RE2O3:B2O3 = 2:3, 1:2, and 3:5 failed under normal-pressure conditions. In contrast, the corresponding high-pressure experiments led in most cases to phase pure rare-earth metal(III) oxoborates RE4B6O15 (RE = Dy, Ho) and α-RE2B4O9 (RE = Sm–Ho), exhibiting the new structural unit of edge-sharing tetrahedra. Our latest experiments yielded in a third compound, exhibiting edge-sharing tetrahedra. The special feature of the compound HP–NiB2O4 is that in contrast to the first two compounds all tetrahedra are linked to each other via one common edge and two common corners
[3].
With the synthesis of β–MB2O5 (M=Zr, Hf) and β–SnB4O7[4]
, we were able to synthesize the first crystalline compounds in the ternary systems Zr–B–O, Hf–B–O, and Sn–B–O, respectively. Normally, these systems form glasses at ambient pressure conditions. No crystalline compounds were known in these systems. Now, the parameter pressure induces crystallization, which leads to defined crystalline compounds in both systems.
The talk will introduce into several examples including the synthesis of new fluoride borates and spinel-type gallium oxonitrides
[5], which impressively underline the importance of the
parameter pressure for the synthesis of new materials in solid state and materials chemistry.
[1] H. Huppertz, Z. Kristallogr. 2004, 219, 330. [2] J. S. Knyrim, P. Becker, D. Johrendt, H. Huppertz, Angew. Chem. 2006, 118, 8419; Angew.
Chem. Int. Ed. Engl. 2006, 45, 8239. [3] J. S. Knyrim, F. Roeßner, S. Jakob, D. Johrendt, I. Kinski, R. Glaum, H. Huppertz, Angew.
Chem. 2007, 119, 9256; Angew. Chem. Int. Ed. Engl. 2007, 46, 9097. [4] J. S. Knyrim, F. M. Schappacher, R. Pöttgen, J. Schmedt auf der Günne, D. Johrendt, H.
Huppertz, Chem. Mater. 2007, 19, 254. [5] H. Huppertz, S. A. Hering, C. E. Zvoriste, S. Lauterbach, O. Oeckler, R. Riedel, I. Kinski,
Chem. Mater. 2009, 21, DOI: 10.1021/cm803371k, in press.
Email: [email protected] Keywords: High-pressure synthesis, Borates, Fluoride Borates, Gallium oxonitrides
37
EHPRG AWARD Pressure-induced phenomena in complex manganese and cobalt oxides:
tuning of magnetic, charge, orbital ordering and spin states.
Denis Kozlenko
Joint Institute for Nuclear Research, 141980 Dubna, Russia
The complex manganese and cobalt oxides R1-xAxMO3-d (R – rare earth, A - alkaline earth elements, M=Mn, Co) demonstrate a rich variety of fascinating physical phenomena which are at the current focus of the extensive research in the field of the condensed matter physics - magnetic and structural phase transitions, Jahn-Teller (JT) effect, insulator-metal (IM) transitions, orbital (OO) and charge (CO) ordering, colossal magnetoresistance, spin state transitions and ordering, ferroelectricity, multiferroic phenomena, etc. Due to strong correlations between lattice, charge, spin and orbital degrees of freedom and competing FM double exchange and AFM superexchange interactions, the nature of the above mentioned physical phenomena observed in these materials and their relationship with the features of the crystal structure, as well as a role of particular competing interactions is far from being understood. In comparison with other experimental techniques, application of high pressure is a direct way of modification of the balance between competing interactions due to controlled variation of interatomic distances and angles. An effective tool for investigation of high pressure effects in magnetic oxides is neutron diffraction, which can provide information about modifications of crystal and magnetic structures simultaneously. In order to explore high pressure effects in complex manganese and cobalt oxides, to reveal interplay between physical and structural properties, and elucidate the role of particular factors in the formation of physical properties a systematic studies of characteristic classes of these materials by complimentary neutron (up to 9 GPa) and X-ray diffraction and Raman spectroscopy methods (up to 40 GPa) were performed. The obtained results demonstrate a number of novel pressure induced phenomena revealed in complex manganese and cobalt oxides. Between them – various modifications of magnetic, orbital and charge order, spin states and spin state order, geometric frustration effects, multiferroic properties, correlated with changes of structural parameters and physical properties [1-9]. The role of competing FM and AFM superexchange interactions, eg orbital order related to anisotropic distortion of MnO6 octahedra and lattice effects in the occurrence of these phenomena was elucidated. The work is supported by RFBR, grant 09-02-00311a.
[1] D.P.Kozlenko et al, J. Phys.: Condens Matter 16 2381 (2004). [2] D.P.Kozlenko et al., J. Phys.: Condens. Matter 16 6755 (2004). [3] D.P.Kozlenko et al., Phys. Part. Nuclei 37(suppl. 1), S1 (2006). [4] D.P.Kozlenko et al., Phys. Rev. B 76, 094408 (2007). [5] D.P.Kozlenko et al., Phys. Rev. B 75, 104408 (2007). [6] D.P.Kozlenko et al., Phys. Rev. B 75, 064422 (2007). [7] D.P.Kozlenko et al., Phys. Rev. B 77, 104444 (2008). [8] D.P.Kozlenko et al., Phys. Rev. B, 78, 054401 (2008). [9] N.O.Golosova, D.P.Kozlenko et al., Phys. Rev. B, 79, 104431 (2009). *E-mail: [email protected] Keywords: neutron diffraction, magnetic structure, orbital order, spin state
38
39
Theory
Lectures Boron under high pressure: a first-principles study ______________________________ 41
Superconductivity in BaSi2, Be2Li and other alloys under pressure __________________ 42
Dynamical properties of tetragonal TbPO4 under pressure from ab initio
calculations. ______________________________________________________ 43
Prediction and determination of the structural parameters of incommensurate
crystal structure in Ca and Sc at high pressure ___________________________ 44
Distortions and low symmetry environments in liquid metals : Na and Li at high
pressure. _________________________________________________________ 45
A simple tight-binding model for the study of the melting properties of 4d
transition metals at extreme conditions ________________________________ 46
First principles studies of icosahedral boron carbides under extreme conditions ______ 47
Elastic properties of iron under pressure: a first-principles study ___________________ 48
Posters TH 01 : Generalized stacking fault energy surfaces and dislocation properties of
coesite ___________________________________________________________ 49
TH 02 : First-principles investigation of gypsum under pressure ____________________ 50
TH 03: Theoretical study of the structural and dynamical properties of HgGa2S4
chalcopyrite under pressure. _________________________________________ 51
Th 04 : Lattice dynamics and structural properties of CuInO2 under high pressure
from ab initio calculations. __________________________________________ 52
TH 05 : Ab initio study of high-pressure structural and vibrational properties of
zircon-type orthovanadates. _________________________________________ 53
TH 06 : Theoretical characterization of the TiSiO4 Possible polymorphs and its
pressure-induced phase transformations _______________________________ 54
TH 07 : Theoretical study of HgSe and HgTe at high pressure ______________________ 55
TH 08 : Ab initio and Raman studies of phase transitions in wolframite-type
CdWO4 at high pressure _____________________________________________ 56
TH 09 : First-principles study of the phonon spectrum of ZnAl2O4 and ZnGa2O4
under high pressure ________________________________________________ 57
TH 10 : Ab initio calculations of the high pressure phase transition in MnWO4 ________ 58
TH 11 : Entropy and high-temperature pressure scales ___________________________ 59
TH 12 : Thermodynamic properties of electrons in metals and semi-empirical
equations of state __________________________________________________ 60
TH 13 : Multiphase equations of state for Be and Mg at high pressures _____________ 61
40
41
Boron under high pressure: a first-principles study
S. I. Simak*1, A. S. Mikhaylushkin1, I. A. Abrikosov1, E. Yu. Zarechnaya2, L. S. Dubrovinsky2, N. Dubrovinskaia2
1Theoretical Physics, Department of Physics, Chemistry and Biology, Linköping University, SE-581 33 Linköping, Sweden
2 Bayerisches Geoinstitut, Universität Bayreuth, 95440 Bayreuth, Germany
Boron is one of the most enigmatic elements in the periodic table. It exhibits a unique structural physics based on icosahedral entities which are linked together in a variety of ways. We analyze bonding situation in boron under pressure from first principles in the framework of the density functional theory. We elucidate the structural and bonding behavior of highly compressed boron, therefore extending the picture presented in Ref.[1]. Structural phase transitions, confirmed by recent experiments and/or predicted by theory are discussed. In particular, we show that bonding in the superhard high-pressure high-temperature phase of boron[2], which has recently became a hot topic[3-4] and reported to be ionic[3], is predominantly covalent. Our theoretical results are supported by experiment[5].
[1] U. Häussermann, S. I. Simak, R. Ahuja, and B. Johansson, Phys. Rev. Lett. 90, 065701 (2003).
[2] R. H. Wentorf Jr. Science 147, 49 (1965) [3] A. R. Oganov, J. Chen, C. Gatti, Y. Ma, Y. Ma, C. W. Glass, Z. Liu, T. Yu, O. O. Kurakevych,
and V. L. Solozhenko, Nature 457, 863 (2009) [4] E.Yu. Zarechnaya, L. Dubrovinsky, N. Dubrovinskaia, N. Miyajima, Y. Filinchuk, D.
Chernyshov, and V. Dmitriev, Sci. Technol. Adv. Mater. 9, 044209 (2008). [5] E. Yu. Zarechnaya, L. Dubrovinsky, N. Dubrovinskaia, Y. Filinchuk, D. Chernyshov, V.
Dmitriev, N. Miyajima, A. El Goresy, H. F. Braun, S. Van Smaalen, I. Kantor, A. Kantor, V. Prakapenka, M. Hanfland, A. S. Mikhaylushkin, I. A. Abrikosov, and S. I. Simak, Phys. Rev. Lett. 2009, to appear.
* E-mail : [email protected]
Keywords : boron, high pressure, bonding, superhard material
42
Superconductivity in BaSi2, Be2Li and other alloys under pressure
A. Bergara1,2,3*, B. Rousseau2, and I. Errea1,2 1 Condensed Matter Physics Department, Faculty of Science and Technology,
University of the Basque Country, E-48080 Bilbao, Basque Country, Spain 2 Donostia International Physics Center (DIPC), Manuel de Lardizabal Pasealekua,
E-20018 Donostia, Basque Country, Spain 3 Centro de Fisica de Materiales CSIC-UPV/EHU 1072 Posta Kutxatila,
E-20018 Donostia, Basque Country, Spain
The discovery of MgB2 probed the success of light element alloys to enhence the superconducting Tc. Actually, its hexagonal layered structure is shared by a large class of alloys with relatively high superconducting transition temperatures, such as CaSi2, BaSi2, ternary silicides and alcaline-earth intecalated graphites.Interestingly, many of these alloys show that their superconducting properties are enhenced with pressure. Additionally, Feng et al. have recently predicted that, although at normal conditions Li and Be are immiscible, under rpressure Be2Li also adopts a MgB2-like structure. In this talk we will present a theoretical analysis of the electronic and superconducting properties of BaSi2, Be2Li and other alloys under pressure.
*E-mail : [email protected]
Keywords: Phonon instabilities, superconductivity binary alloys
43
Dynamical properties of tetragonal TbPO4 under pressure from ab initio calculations.
J. López-Solano*, A. Muñoz, and P. Rodríguez-Hernández
MALTA Consolider Team - Departamento de Física Fundamental II, and Instituto de Materiales y Nanotecnología, Universidad de La Laguna, La Laguna, Tenerife, Spain
Terbium phosphate TbPO4, along with several other RPO4 (R = heavy rare-earth ion, Tb to Lu) compounds, normally crystallizes in the tetragonal zircon (ZrSiO4) structure. Recently Tatsi et al. [1] have reported a Raman study of TbPO4 under pressure up to 15.5 GPa, providing experimental evidence of a first-order phase transition around 9.5 GPa to a not completely determined structure, although monazite has been suggested as a likely candidate.
In this work we present a theoretical first principles study of the structural and dynamical properties of TbPO4 under hydrostatic pressure. The calculations are performed in the framework of the density functional theory (DFT) and the pseudopotential plane-wave (PPW) approach. Results of the evolution under pressure of the structural parameters, electronic properties, and phonon frequencies at the zone-center are reported. The later have been obtained by means of the direct force constant method, in which the dynamical matrix is constructed from the forces obtained when single-atom displacements are applied to the equilibrium configuration of a structure. Symmetry considerations can be used to identify a set of independent distortions, thus reducing the computational effort. The construction of the dynamical matrix at the Gamma point is particularly simple, since it involves working just with the primitive unit cell. Diagonalization of the dynamical matrix then provides both the frequencies of the normal modes and their polarization vectors, allowing us to identify the irreducible representation and character of the phonon modes.
[1] A. Tatsi, E. Stavrou, Y.C. Boulmetis, A.G. Kontos, Y.S. Raptis and C. Raptis, J. Phys. Cond. Matt. 20, 425216 (2008).
* E-mail : [email protected]
Keywords: ab initio, structural and dynamical properties
44
Prediction and determination of the structural parameters of incommensurate crystal structure in Ca and Sc at high pressure
S. Arapan and R. Ahuja
Condensed Matter Theory Group, Department of Physics & Materials Science Uppsala University, 75121 Uppsala, Sweden
We predict an incommensurate high-pressure phase of Ca [1] and determine the structural parameters of incommensurate phase for Sc [2] from first principle calculations and describe a procedure of estimating incommensurate structure parameters by means of electronic structure calculations for periodic crystals. We predict incommensurate phase above 122 GPa
for Ca. Our results for Sc show that (cH/cG) increases with pressure up to 60 GPa approaching but never reaching the commensurate value 4/3. Hence calculations do not confirm the prediction made based on the reanalyzing of experimental data. When pressure exceeds 70
GPa, shows a sharp decrease that might be considered as the precursor of a new structural phase transition.
[1] S.Arapan, H.K.Mao and R.Ahuja, Proc. Nat. Acad. Sciences, USA, 105, 20627 (2008). [2] S.Arapan, N.V. Skorodumova and R.Ahuja, Phys. Rev. Lett. 102, 085701 (2009).
*E-mail : [email protected]
Keywords: Metals, Crystal Structure, ab initio Theory,
45
Distortions and low symmetry environments in liquid metals : Na and Li at high pressure.
J.Y. Raty1, E. Schwegler2, I. Tamblyn3 and S. Bonev2 1Physics Department, FNRS-University of Liège, Liège, Belgium
2Quantum Simulation Group, Lawrence Livermore National Laboratory, Livermore, USA 3Physics Department, Dalhousie University, Halifax, Canada
The melting curve of sodium measured in exhibits totally unexpected features under pressure: the melting temperature, Tm, reaches a maximum around 30 GPa followed by a sharp decline from 1000 K to 300 K in the pressure range from 30 to 120 GPa
[1].
In the present study, the structural and electronic properties of molten sodium and lithium are studied using first principles theory. With increasing pressure, both liquids evolve by assuming a more compact local structure, which accounts for the maximum of Tm at 30 GPas in Na and the flattening of the melting curve in Li. However, at pressure around 65 GPa in Na and 20 GPa in Li a transition to a lower coordinated structure takes place, driven by the opening of a pseudogap at the Fermi level
[2]. Remarkably, the 'broken symmetry' liquid phase
emerges at rather elevated temperatures and above the stability region of a closed packed free electron-like metal. The theory explains the measured drop of the sodium melting temperature, down to 300 Kelvin at 105 GPa. The behavior of Li at higher pressure is even more surprising as we evidence the emergence of tetrahedrally (slightly) bonded clusters as due to increased core-core overlap
[3].
[1] E. Gregoryanz, O. Degtyareva, M. Somayazulu, R. Hemley, H. Mao, Phys. Rev. Lett. 94, 185502 (2005).
[2] J.Y. Raty, E. Schwegler, S. Bonev, Nature 449, 448 (2007) [3] I. Tamblyn, J.Y. Raty, S. Bonev, Phys. Rev. Lett. 101, 075703 (2008)
* E-mail : [email protected]
Keywords : High-pressure, Liquids, Phase transition, Metal
46
A simple tight-binding model for the study of the melting properties of 4d transition metals at extreme conditions
C. Cazorla1,2, D. Alfé1,2,3,4 and M. J. Gillan1,2,3
1Materials Simulation Laboratory, London, U.K. 2Earth Sciences Department, University College London, London, U.K.
3London Center for Nanotechnology, London, U.K. 4Physics and Astronomy Department, University College London, London, U.K.
Very recently [1], we have developed a simple tight-binding (TB) model of transition metals in the region near the middle of the 4d-series, tuned to mimic molybdenum. The melting properties deriving from this model are quite close to those obtained in previous first principles work on Mo [2]. TB approaches, reasonably accurate but computationally not as demanding as first-principles calculations, then can be useful in performing systematic studies aimed at resolving the existing large discrepancies between static compression DAC data, on one hand, and shock-wave dynamic experiments and theoretical investigations, on the other, on the melting properties of transition metals [3,4]. Here, we present a series of TB parametrization designed to emulate the behavior of niobium, technetium, ruthenium, rhodium and palladium under extreme conditions of pressure and temperature. Our simple TB model is composed of two basic contributions to the energy: first, the pairwise repulsion due to Fermi exclusion, and second, the d-band bonding energy described in terms of an electronic density of states that depends on structure. The parameters of the model are adjusted to fit the dependence on pressure of the d-band width and the zero-temperature equation of state of the element in question. Calculated TB phonon spectra compare generally well with existing ab initio data and measurements performed on 4d transition metals.
[1] C. Cazorla, D. Alfé, and M. J. Gillan, J. of Chem. Phys. 130, 1 (2009) [2] C. Cazorla, M. J. Gillan, S. Taioli, and D. Alfé, J. of Chem. Phys. 126, 194502 (2007) [3] C. Cazorla, D. Alfé, and M. J. Gillan, Phys. Rev. Lett. 101, 049601 (2008) [4] D. Errandonea, Physica B : Condensed Matt. 357, 356 (2005)
* E-mail : [email protected]
Keywords : transition metals, melting, tight-biding, modeling
47
First principles studies of icosahedral boron carbides under extreme conditions
E. Betranhandy, N. Vast and J. Sjakste
Laboratoire des Solides Irradiés, CEA Direction des Sciences de la Matière - CNRS UMR7642 - École Polytechnique, 91128 Palaiseau, France
Boron carbides constitute a class of materials of industrial interest due to their remarkable mechanical properties, used in cutting tools for example. However, they can not be used as protective materials as they do not sustain shockwaves. In order to understand this behavior, we have investigated the evolution of their physical properties under extreme conditions such as high pressure and high temperature with theoretical methods based on the well-established density functional theory (DFT)
[1] and density functional perturbation theory
(DFPT)[2]
.
The atomic structure of boron carbide (B4C) mainly consists in B11C icosahedra (with C in polar site) linked by CBC chains
[3-5]. We have investigated many other phases with various carbon
concentrations and found that most of our structural models are metastable with respect to B4C
[6].
For structures which present a vacancy, we find that a structural modification does occur under pressure. Moreover, calculated transition pressure is in good agreement with experimental observations
[7]. Occurrence of these structures as defects in experimental
samples yields an explanation about why boron carbides do not sustain shockwaves.
[1] http://nobelprize.org/nobel_prizes/chemistry/laureates/1998/kohn-lecture.html [2] S. Baroni, S. de Gironcoli, A.D. Corso, and P. Giannozzi, Rev. Mod. Phys. 73, 515 (2001). [3] F. Mauri, N. Vast and C.J. Pickard, Phys. Rev. Lett. 87, 085506 (2001). [4] R. Lazzari, N. Vast, J.M. Besson, S. Baroni and A. Dal Corso, Phys. Rev. Lett. 83, 3230 (1999);
Ibid 85, 4194 (2000). [5] M. Calandra, N. Vast and F. Mauri, Phys. Rev. B 69, 224505 (2004). [6] N. Vast, J. Sjakste and E. Betranhandy, Journal of Physics: Conference Series, under press
(2009). [7] T. J. Vogler, W. D. Reinhart, and L. C. Chhabildas, J. Appl. Phys. 95, 4173 (2004).
*E-mail : [email protected]
Keywords : boron carbides, structural defects, density functional theory
48
Elastic properties of iron under pressure: a first-principles study
O. Y. Vekilova*, A. S. Mikhaylushkin, S. I. Simak, I. A. Abrikosov
Theoretical Physics group, Department of Physics, Chemistry and Biology, Linköping University, SE-58183 Linköping, Sweden
First-principles studies of materials at the Earth’s inner core conditions are of great importance since the corresponding high-pressure high-temperature conditions (around 6000 K and 360 GPa, respectively) are not yet accessible experimentally. It is generally presumed that the Earth’s inner core consists of iron alloyed with small amounts of nickel and a few percent of light elements such as sulphur or silicon. However, even the crystalline structure of pure iron at the Earth’s inner core conditions is still under discussion. Until recently the hexagonal close packed (hcp) phase of iron was considered as the only candidate for the Earth’s inner core, but it has lately been shown that the free energy differences among the hcp and the cubic (body centred cubic (bcc) and face-centred-cubic (fcc)) phases of iron are very small on the temperature scale. We present a theoretical study of elastic properties of the cubic phases of Fe and Fe-based alloys at the Earth’s inner core conditions. It is based on the density functional theory and molecular dynamics simulations. We calculate the elastic moduli using different approaches and compare them. The obtained results might have important implications for the Earth’s core and high-pressure physics.
*Email : [email protected]
Keywords: Fe alloys, high pressure, molecular dynamics, elastic properties
49
Generalized stacking fault energy surfaces and dislocation properties of coesite
L. Giacomazzi*, S. Scandolo
CNR-INFM/Democritos National Simulation Center and the Abdus Salam International Centre for Theoretical Physics (ICTP), Strada Costiera 11, I-34151, Trieste, Italy.
Coesite, the densest silica polymorph in which silicon is tetrahedrally coordinated to oxygen, can be found in rocks that have experienced high pressures such as in meteorite impacts and in low-temperature, high-pressure metamorphism. Despite its geophysical relevance, the deformation processes, slip systems and rheological laws of coesite are still unclear[1-2]. We use a very accurate interatomic potential for silica, the parameters of which were extracted from ab-initio calculations[3]. For the adopted potential we calculated the elastic constants of coesite that are found in reasonably good agreement with experiments. We have primarily investigated a selected set of slip systems in coesite, in the framework of the Peierls-Nabarro model[4]. Two-dimensional generalized stacking fault energy surfaces for basal and prismatic planes are considered for a global search of the possible dissociation paths in partial dislocations.Work supported by CNR under ESF/Eurocores program ``EuroMinSci''.
[1] F. Langenhorst and J. P. Poirier, Earth Planet. Sci. Lett. 203, 793 (2002). [2] H. Idrissi, P. Cordier, D. Jacob, N. Walte, Eur. J. Mineral. 20, 665 (2008). [3] P. Tangney and S. Scandolo, J. Chem. Phys. 117, 8898 (2002). [4] F. R. N. Nabarro, Proc. Phys. Soc. London 59, 256 (1947).
*E-mail : [email protected]
Keywords: Coesite, dislocations
50
First-principles investigation of gypsum under pressure
L. Giacomazzi*, S. Scandolo
CNR-INFM/Democritos National Simulation Center and the Abdus Salam International Centre for Theoretical Physics (ICTP), Strada Costiera 11, I-34151, Trieste, Italy.
Hydrous minerals are important for the investigation of the dynamics in the Earth's mantle[1]. They contribute to the hydration and hence to the seismic anisotropy of subducting oceanic plates[2]. Among the various hydrous minerals, we consider a very common evaporitic mineral: gypsum. We carry out a first-principles investigation of gypsum aimed at understanding the structural changes induced by pressures up to 8 GPa, within and above the stability range of gypsum (P < 4 GPa)[3]. Bond lengths and volumes of SO4 and CaO8 polyhedra are found to show similar pressure behavior as in experiment. The most noticeable changes in the structure concern the reduction of the hydrogen bond-lengths and the decrease in volume of the CaO8 polyhedra[3]. Moreover, we have calculated from first-principles infrared and Raman spectra of gypsum up to 8 GPa. An overall good agreement is found with experimental vibrational frequencies and their pressure behavior, thereby validating the adopted methodology and providing a theoretical basis for the mode assignements.
Work supported by CNR under ESF/Eurocores program ``EuroMinSci''.
[1] C. Meade and R. Jeanloz, Science 252, 68 (1991). [2] M. Faccenda, L. Burlini, T. V. Gerya, and D. Mainprice, Nature 455, 1097 (2008). [3] P. Comodi, S. Nazzareni, P. F. Zanazzi, and S. Speziale, Am. Mineral. 93, 1530 (2008).
*E-mail : [email protected]
Keywords: Gypsum, first-principles
51
Theoretical study of the structural and dynamical properties of HgGa2S4 chalcopyrite under pressure.
E. Pérez-González*, P. Rodríguez-Hernández, and A. Muñoz
MALTA Consolider Team - Departamento de Física Fundamental II, and Instituto de Materiales y Nanotecnología, U niversidad de La Laguna, La Laguna, Tenerife, Spain
The ternary AB2X4 defect chalcopyrite compounds display photoconductive and nonlinear optical properties competitive with those of ABX2 chalcopyrite compounds. Mercury thiogallate, HgGa2S4, is and ordered-vacancy semiconductor of the AIIB2IIIX4VI family that crystallizes in the defect chalcopyrite structure (I 4 ), with high nonlinear optical coefficients and wide transparency range. In this work we present a theoretical first principles study of structural and the dynamical properties of HgGa2S4 under hydrostatic pressure. The calculations are performed in the framework of the density functional theory, DFT, and the pseudopotential plane-wave PPW approach. The dynamical matrix was calculated by means of the direct method. We will present results of the evolution of the structural and electronic properties under pressure. The phonon frequencies at the zone-center and the pressure coefficients will be reported.
*E-mail : [email protected]
Keywords: ordered-vacancy semiconductors, chalcopyrites, ab initio, dynamical properties
52
Lattice dynamics and structural properties of CuInO2 under high pressure from ab initio calculations.
E. Pérez-González, P. Rodríguez-Hernández, A. Muñoz
MALTA Consolider Team - Departamento de Física Fundamental II, and Instituto de Materiales y Nanotecnología, U niversidad de La Laguna, La Laguna, Tenerife, Spain
Transparent conductive oxides (TCO) are materials of considerable technological interest with applications in solar cells, transparent electrodes in flat panel displays, etc. In this work we present an ab initio study of the vibrational and structural properties of the CuInO2 delafossite under hydrostatic pressure. We adopt the density functional theory, DFT, and the local density approximation, LDA, within the plane wave pseudopotential method. We use thedensity functional perturbation theory, DFPT, in order to obtain the phonon dispersion curve, the phonon frequencies and pressure coefficients of CuInO2. Finally we investigate the pressure dependence of different phonon branches and we found a dynamical instability as origin of the phase transition of CuInO2 under pressure.
*E-mail : [email protected]
Keywords: ab initio, dynamical and structural properties
53
Ab initio study of high-pressure structural and vibrational properties of zircon-type orthovanadates.
P. Rodríguez-Hernández, J. López-Solano*, and A. Muñoz
MALTA Consolider Team - Departamento de Física Fundamental II, and Instituto de Materiales y Nanotecnología, Universidad de La Laguna, La Laguna, Tenerife, Spain
Orthovanadates with formula AVO4, where A is a trivalent element, are interesting materials from the point of view of their utilization in solid-state lasers or scintillators, for example. The properties of these compounds under normal conditions have been thoroughly studied, and it is well stablished that most AVO4 compounds crystallize in the zircon-type structure. Recently, room temperature angle-dispersive x-ray diffraction (ADXRD) measurements under pressure on EuVO4, LuVO4, and ScVO4 were performed up to 27 GPa by Errandonea et al [1]. They found evidence of a pressure-induced structural phase transition from the zircon to a scheelite-type structure in all three compounds. A second transition was observed in EuVO4 and LuVO4, and although the quality of the diffraction patterns did not allow to perform Rietvel refinements, a M-fergusonite-type structure was suggested as the third stable phase under pressure.
To help in the understanding of the behaviour of orthovanadates under pressure, in this work we present results of our own ab initio study, carried out within the framework of the density functional theory (DFT) and pseudopotential method. The projector-augmented wave (PAW) scheme was adopted, with the formulation of Perdew-Burke-Ernzerhof (PBE) for the calculation of the exchange and correlation energy, and the Monkhorst-Pack prescription for integrations in the Brillouin-zone. We have started by performing total-energy calculations in which we have checked the relative stability of different structures which are likely candidates of being stable at different pressures. At each selected volume, all the structures have been fully relaxed to their equilibrium configuration while keeping the crystal symmetry fixed. The structural parameters obtained from these calculations can be compared with the experimental results. We have also performed lattice-dynamic calculations using the direct force constant approach (also known as the supercell method). The calculation of the frequencies and polarization vectors of the normal modes at the Γ point is particularly simple and involves the displacement of each atom by separate from the equilibrium configuration of the primitive cell. A set of independent displacements can be obtained by taking into account the symmetry of the structure. The results of these calculations can be directly compared with Raman and Infrared spectroscopy measurements.
[1] D. Errandonea, R. Lacomba-Perales, J. Ruiz-Fuertes, A. Segura, S. N. Achary, and A. K. Tyagi, Phys. Rev. B, in press (2009).
* E-mail : [email protected]
Keywords: ab initio, structural and dynamical properties
54
Theoretical characterization of the TiSiO4 Possible polymorphs and its pressure-induced phase transformations
L. Gracia1*, A. Beltrán1 and D. Errandonea2 1MALTA Consolider Team, Departament de Química Física I Analítica, Universitat Jaume I,
Campus de Riu Sec, Castelló E-12080, Spain 2MALTA Consolider Team, Departament de Física Aplicada – ICMUV, Fundació General de la
Universitat de València, 46100 Burjassot (Valencia), Spain
Theoretical investigations concerning the possible titanium silicate polymorphs have been performed using density functional theory at B3LYP level using the CRYSTAL06 program package [1]. Total-energy calculations and geometry optimizations have been carried out for all phases involved. The following sequence of pressure-driven structural transitions has been found: CrVO4-type (Cmcm) → zircon-type (I41/amd) → scheelite-type (I41/a) → fergusonite-type (C2/c). The equation of state of the different polymorphs is also reported. We found that the highest bulk modulus corresponds to the zircon phase with a value of 248 GPa, while the corresponding values for scheelite and fergusonite phases are slightly lower (238 and 241 GPa, respectively). The orthorhombic Cmcm phase is the most compressible of all the studied structures with a bulk modulus of only 124 GPa, being also the most stable phase at ambient pressure. Possible reasons for the largest compressibility of CrVO4-type TiSiO4 are proposed based upon the differences of its local atomic structure with those of the other polymorphs. Finally, calculations of the electronic structure, vibrational and dielectric properties of TiSiO4 are also presented and compared to limited pre-existing studies [2].
[1] R. Dovesi, V. R. Saunders, C. Roetti, R. Orlando, C. M. Zicovich-Wilson, F. Pascale, B. Civalleri, K. Doll, N. M. Harrison, I. J. Bush, Ph. D’Arco, M. Llunell, CRYSTAL06 User's Manual (University of Torino, 2006).
[2] G. M. Rignanese, X. Rocquefelte, X. Gonze, and A. Pasquarello, Int. Journ. Quant. Chem. 101, 793 (2005).
*E-mail : [email protected]
55
Theoretical study of HgSe and HgTe at high pressure
S. Radescu*1, A.Mujica1, A. Muñoz1, and R.J. Needs2 1MALTA Consolider Team – Departamento de Física Fundamental II and Instituto de
Materiales y Nanotecnología, Universidad de La Laguna, La Laguna 38205, Tenerife, Spain 2Theory of Condensed Matter group, Cavendish Laboratory, Cambridge University,
19 J.J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom
HgSe and HgTe go through the same experimental sequence of structural changes under increasing compression[1]. The zincblende phase, which is semimetallic and stable under normal conditions, transforms into a cinnabar-like semiconducting phase at the rather moderately high pressure of about 1 GPa. If pressure is further increased (to ~15 GPa in HgSe and ~8 GPa in HgTe) the cinnabar phase transforms into the NaCl-type structure and at even higher pressures (~28 GPa in HgSe and ~10 GPa in HgTe) this NaCl phase transforms in turn into the Cmcm phase, so named after its space group. The Cmcm structure is an orthorhombic distortion of the NaCl structure, and plays an important role in the high-pressure behavior of the II-VI and III-V families of binary compounds, where it is adopted by many of its members at high enough pressure[1,2]. At a lower pressure range, an interesting feature of both HgSe and HgTe is the observation of a transition from the zincblende phase to an orthorhombic phase with space group C2221 which is a distortion of zincblende[1] . The C2221 phase is observed at pressures at which the sluggish zincblende→cinnabar transition has already begun but has not yet been completed, and it transforms into the cinnabar phase as the pressure is further increased. In this work we show the results of a first-principles theoretical study of HgSe and HgTe under high pressure, performed within the framework of the density functional theory and the plane-wave pseudopotential scheme. We study both the energetics and local dynamical stability of the structural phases, focusing particularly on the “hidden” transition to the C2221 phase. Our study sheds light on the nature of the transitions and the stability of the phases under compression, and reveals peculiarities in the behavior of these materials within the II-VI and related III-V families. We provide a full structural evolution of the phases and detailed comparisons with existing experimental results.
[1] R.J. Nelmes and M.I. McMahon, Semiconductors and Semimetals 54, 145 (2008). [2] A. Mujica, A. Rubio, A. Muñoz, and R.J. Needs, Rev. Mod. Phys. 75, 863 (2003).
*E-mail : [email protected]
Keywords: Mercury chalcogenides, structural stability, high pressure, computational methods
56
Ab initio and Raman studies of phase transitions in wolframite-type CdWO4
at high pressure
A. Mujica1*, P. Rodríguez-Hernández1, S. Radescu1, A. Muñoz1, R. Lacomba-Perales2, D. Errandonea3, D. Martínez-García2, J. C. Chervin4, and A. Polian4
1MALTA Consolider Team, Departamento de Física Fundamental II, and Instituto de Materiales y Nanotecnología, Universidad de La Laguna, La Laguna 38205, Tenerife, Spain
2MALTA Consolider Team, Departamento de Física Aplicada - ICMUV, Universitat de València, Edificio de Investigación, C/ Dr. Moliner 50, 46100 Burjassot, Valencia, Spain
3MALTA Consolider Team, Departamento de Física Aplicada - ICMUV, Fundación General de la Universitat de València, Edificio de Investigación, C/ Dr. Moliner 50, 46100 Burjassot,
Valencia, Spain 4Institut de Minéralogie et de Physique des Milieux Condensés, Université Pierre et Marie
Curie, Paris 6 et 7, CNRS UMR 7590, 140 rue de Lourmel, F-75015 Paris
Metal tungstates are a relevant class of inorganic compounds with many practical applications including laser crystals, catalysis, and scintillation detectors. Cadmium tungstate CdWO4, a member of this family, is a wide-gap semiconductor with fundamental energy gap close to 4 eV. At ambient conditions it crystallizes in the wolframite structure. In this work we have studied the energetics of the wolframite phase of CdWO4 as well as several other high-pressure candidate structural phases and have performed a detailed comparison with high-pressure experimental results. The calculations (which included the evolution of the phonon frequencies at the zone center) were done within the framework of the density-functional theory (with exchange-correlation contribution approximated by a generalized gradient form) and the plane wave pseudopotential method. Our ab initio total-energy and lattice-dynamics calculations for the different phases of CdWO4 were combined with roomtemperature Raman scattering experiments performed up to 43 GPa. This combination of computational methods and experimental techniques helped in the characterization of the crystalline structure of the observed high-pressure phases. Experimental and theoretical results suggest the coexistence of two structures from 20 to 35 GPa, one with tetragonal symmetry and the other with triclinic symmetry. Beyond 35 GPa the monoclinic b-fergusonite structure is proposed as that of the stable phase of CdWO4 [1].
[1] R. Lacomba-Perales, D. Errandonea, D. Martinez-Garcia, P. Rodríguez-Hernández, S. Radescu, A. Mujica, A. Muñoz, J. C. Chervin, and A. Polian, Phys. Rev. B 79, 094105 (2009).
* E-mail : [email protected]
Keywords: cadmium tungstate, structural and dynamical properties, ab initio computational methods, Raman
57
First-principles study of the phonon spectrum of ZnAl2O4 and ZnGa2O4 under high pressure
S. López1*, A. Muñoz2, P. Rodríguez-Hernández2, and A. H. Romero1 1CINVESTAV-Queretaro Libramiento Norponiente No 2000 Real de Juriquilla
76230 Queretaro, Qro, México. 2MALTA Consolider Team, Departamento de Física Fundamental II, and Instituto de
Materiales y Nanotecnología, Universidad de La Laguna, La Laguna 38205, Tenerife, Spain
Cubic oxide spinel AM2O4 compounds (A: bivalent cation and M: trivalent cation) occur in many geological settings of the Earth’s crust and mantle, as well as in lunar rocks and meteorites. The study of their high-pressure structural properties is important for improving the understanding of the constituents of our planet. In this work we present total energy calculations of zinc gallate, Zn Ga2O4, and gahnite, ZnAl2O4, cubic spinels, under hydrostatic pressure. The calculations (which include the evolution of the phonon frequencies at the zone center) were done within the framework of the density-functional theory (with exchange-correlation contribution approximated by the local density approximation, LDA) and the plane wave pseudopotential method. We will present the results of our ab initio total-energy and lattice-dynamics calculations, reporting the phonon-dispersion, the Raman, and the Infrared modes, the pressure coefficients and the Grüneissen parameters, of the ambient pressure phase and for the recently reported high pressure phases of both compounds [1,2]
[1] D. Errandonea, R. S. Kumar, F.J. Manjón, V. Ursaki, and E. Rusu, Phys. Rev. B 73, 0205204, (2009).
[2] Sinhué López, P. Rodríguez-Hernández, A. H. Romero, and A. Muñoz, Phys. Rev B, in press (2009).
* E-mail : [email protected]
Keywords: Zinc Gallate and gahnite, dynamical properties, ab initio computational methods, Raman
58
Ab initio calculations of the high pressure phase transition in MnWO4
S. López1*, A. Muñoz2, P. Rodríguez-Hernández2 and A. H. Romero1 1CINVESTAV-Queretaro Libramiento Norponiente No 2000 Real de Juriquilla
76230 Queretaro, Qro, México. 2MALTA Consolider Team, Departamento de Física Fundamental II, and Instituto de
Materiales y Nanotecnología, Universidad de La Laguna, La Laguna 38205, Tenerife, Spain
The ABO4 compounds have been studied intensively for several decades, mainly due to their interesting optical and electronic properties. These compounds crystallize in different structures depending on the size and charge of cations. In the literature one can find many reports about the characterization of various properties in a large set of compounds ABO4 (A = Ca, Sr, Cd, Zn, Pb, B = Mo, W). Given the importance of these compounds, in the last decade there has been a lot of work on the effects that suffer when subject to high pressures [1, 2]. In this work we perform an ab initio density functional theory study of the wolframite structure and the possible high pressure phase transitions in MnWO4 compound. Also in this work, we perform a comparison of our results with other phase transitions for similar ABO4 compounds, e.g. MgWO4.
[1] D. Herrandonea, F. Manjón, Progress Mat. Sci. 53, 711 (2008). [2] J. López-Solano, P. Rodriguez-Hernández, et al., Phys. Stat. Sol. (b) 244, 325 (2007)
* E-mail: [email protected]
Keywords: ABO4 compounds, wolframite MnWO4, phase transitions, ab initio calculations
59
Entropy and high-temperature pressure scales
P. I. Dorogokupets*
Institute of the Earth’s Crust, Irkutsk, Russia
At high temperature (T > D/2) the quasiharmonic phonon part of the Helmholtz free energy in the Debye approach (Zharkov et al, 1971) can be replaced by the Einstein model,
)/exp(1lnR3 TTnqh
F (Girifalco, 1973), without loss of accuracy. Differentiating this
expression with respect to volume and temperature and adding a room-temperature isotherm and term describing intrinsic anharmonicity we receive pressure and entropy in the Mie-Grüneisen-Einstein approach:
,10R2
310
1)/exp(1)/exp(R3
1)'4(4
31
2
3),(
3
0
20
20
3
00
3/23/53/70
xV
mTTxan
xVTTn
xKxxKTVP
m (1)
00
0
0
00
00 exp1ln1)/exp(
/exp1ln
1)/exp(
/3
0TTxa
TT
T
TT
TnRSS m
TT(2)
where K0 (GPa) is the isothermal bulk modulus, K = dK0/dP, x = V/V0, V0 (cm3) is volume at the
reference condition, R = 8.3145 J mol–1
K–1
is the gas constant, n is the number of atoms per a unit cell, is the volume dependent Einstein temperature, which corresponds with the Debye temperature as E=D(3/5)
0.5≈0.755xD, = –(ln/lnV)T, ]/)1)(exp[( 00
xx
(Al'tshuler et al., 1987), x)( 0 , T0 is the reference temperature (298.15), a0 (K)
and m are intrinsic anharmonicity parameters. We have all reasons to hold, that P-V-T relations calculated from much more complex equations of state can be approximated by the equation (1) with reasonable accuracy.
Fig. 1. Calculated entropy of MgO and Pt in comparison with thermochemical data.
Solving equation (1) for x at given T and P=0, we can calculate entropy from equation (2), which should coincide with the thermochemical data. However, Fig. 1 shows that most of EoSs of MgO and Pt do not pass the test on entropy, and deviations for MgO and Pt have a different sign. Hence, they misrepresent the calculated pressure up to several GPa at expansion and at compression x~1.
In this report we shall discuss these problems and new self-consistent high-temperature pressure scales on base of thermodynamic equations of state.
This work was supported by the Russian Foundation for Basic Research (No. 09-05-00208).
*E-mail : [email protected]
70
80
90
100
110
120
130
1400 1700 2000 2300 2600 2900Temperature (K)
ST -
S298 (
J(m
ol K
)-1)
Dorogokupets & Oganov 2007Robie et al. 1978Gurvich et al. 1981Wu et al. 2008Tange et al. 2009Speziale et al. 2001, # 1Speziale et al. 2001, # 2Brosh et al. 2008Kennett & Jackson 2009+/- 5%
MgO
30
40
50
60
1000 1300 1600 1900
Temperature (K)
ST -
S2
98 (
J(m
ol K
)-1)
Dorogokupets & Oganov 2007
Robie et al. 1978Sun et al. 2008
Matsui et al. 2009
Fei et al. 2007
Holmes et al. 1989Zha et al. 2008
+/- 5%
Pt
60
Thermodynamic properties of electrons in metals and semi-empirical equations of state
P.R. Levashov*,M.E. Veysman, K.V. Khishchenko
Joint Institute for High Temperatures, Moscow, Russia
Thermodynamic properties of electrons are important under strongly non-equilibrium conditions of femtosecond laser irradiation. Most often these properties are not required directly, but modern femtosecond laser facilities increase the importance of this knowledge. Two-temperature hydrodynamic simulation requires equations of state both for ions and electrons. Traditionally the equation of states for electronic subsystem is calculated using the density functional theory.
On the other hand, in semiempirical equations of state free electrons in metals are considered as independent and one uses the equation of state of ideal Fermi-gas. In order to approximately take into account the interaction between electrons and excitation of electrons one could use more realistic expression for the density of states of electrons in metals. In this work we use the results of DFT calculations by two codes [1] and [2] of a density of states of Ag and Au and derive a simple thermodynamic model for the description of influence of d-electrons of these metals. We consider heat capacity, isothermal sound velocity, and electron-phonon coupling constant and note significant distinction of these values from the ideal Fermi-gas model as it was stated earlier [3]. These improvements are being included into the existing wide-range equations of state for metals.
The authors thank G. V. Sin’ko and N. A. Smirnov for helpful discussions. This work has been doing under RFBR financial support, grants 08-08-01055 and 09-08-01129.
[1] G. Kresse, J. Hafner, Phys. Rev. B 47, 558 (1993); ibid. 49, 14251 (1994). [2] S.Yu. Savrasov, Phys. Rev. B 54, 16470 (1996). [3] Z. Lin, L. V. Zhigilei, Phys. Rev. B 77, 075133 (2008).
*E-mail : [email protected]
Keywords : DFT, thermodynamics of electrons, EOS
61
Multiphase equations of state for Be and Mg at high pressures
K. V. Khishchenko*
Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow, Russia
Equations of state for metals at high pressures are interesting for both basic researches and applications. In this work, a thermodynamic approach to modeling of phase diagrams for metals over a wide range of densities and temperatures is used. New multiphase equations of state for beryllium and magnesium are presented with taking into account polymorphic transitions, melting and evaporation effects. Thermodynamic characteristics of the materials are calculated, and obtained results are compared with available experimental data at high pressures. Proposed equations of state can be used efficiently in numerical simulations of different high-pressure processes.
*E-mail : [email protected]
Keywords : Equation of state, phase diagram, beryllium, magnesium
62
63
Food Sciences
Lectures Association, dissociation and interactions of milk proteins under pressure ___________ 65
Pasting properties of high pressure treated starch suspensions ____________________ 66
Influence of high pressure and elevated temperature on bacterial spores-
inactivation mechanisms above 500 MPa ______________________________ 67
In-situ Investigation of the Turbulent-Laminar Transition of Temperature
Fluctuation during the Pressure Building up to 300 MPa __________________ 68
Rheological properties of biomatter at high pressure – measurement techniques
and relevance for high pressure processes ______________________________ 69
IgE Binding of Apple Allergens Preserved after Treatments at High Pressure _________ 70
Influence of high pressure treatment on allergenicity of rDau c1 and carrot juice
demonstrated by in vitro and in vivo tests ______________________________ 71
Textural properties of fresh cheese made from milk treated by Ultra-High
Pressure Homogenisation ___________________________________________ 72
Posters FS 01 : Citrinin Inactivation Model Study by High Hydrostatic Pressure Treated
Black Table Olives __________________________________________________ 73
FS 02 : Allergenicity of main celery allergen rApi g1 and high pressure treatment _____ 74
FS 03 : Thermal diffusivity estimation of mashed potatoes and olive oil at high
pressure __________________________________________________________ 75
FS 04 : Allergenicity of main birch allergen rBet v1 and high pressure treatment ______ 76
FS 05 : High hydrostatic pressure effects on lactic acid bacteria (LAB), oleuropein
hydrolizing capacity and aerobic mesophilic bacteria of black table
olives: differantions by chemometrics _________________________________ 77
FS 06 : The effect of high pressure on selected physiological properties of
Lactobacillus species________________________________________________ 78
FS 07 : Effect of pressurization on antibacterial properties of Lactobacillus
strains ___________________________________________________________ 79
FS 08 : High pressure processing of foods and packaging materials _________________ 80
FS 09 : Antibiotic resistance of pressurized strains of the Lactobacillus species________ 81
FS 10 : Effects of high pressure on colour and polyphenoloxidase, peroxidase and
β-glucosidase activities in the strawberry puree _________________________ 82
FS 11 : Determination of the isobaric heat capacity of liquid samples by solution
of the heat diffusion equation ________________________________________ 83
FS12 : Observations of a high pressure phase creation in oleic acid _________________ 84
FS13 : Determination of thermodynamic parameters of oleic acid under high
pressure. _________________________________________________________ 85
64
FS 14 : Raman spectroscopy research of triolein under high pressure _______________ 86
FS 15 : The compressibility studies of some vegetable oils up to 1 GPa ______________ 87
FS 16 : Pressure-induced changes in electronic absorption spectrum in oleic acid _____ 88
FS 17 : High pressure inactivation of Pseudomonas in black truffle. Comparison
with Pseudomonas fluorescens in tryptone soya broth ____________________ 89
FS 18 : Submicron emulsions processed by ultra-high pressure homogenisation ______ 90
FS 19 : Cell cultures as a biological tool to study effects of high-pressure
processing on food components ______________________________________ 91
FS 20 : Inactivation of Mycobacterium smegmatis in skimmed and whole milk by
means of high hydrostatic pressure ___________________________________ 92
FS 21 : Pressure unfolding of the apple main allergen Mal d1. An in situ high
pressure FTIR study ________________________________________________ 93
FS 22 : High pressure treatment of marinated poultry products to improve shelf
life and modify meat structure _______________________________________ 94
FS 23 : Effect of combined high pressure–temperature treatments with different
pressurization gradients and NaCl content on the texture of sausage
batter ___________________________________________________________ 95
65
Association, dissociation and interactions of milk proteins under pressure
A.L. Kelly1 * and T. Huppertz2 1 Department of Food and Nutritional Sciences, University College Cork, Ireland
2 NIZO food research, Ede, The Netherlands
The milk protein system, includes two major families of proteins with very different properties, i.e., the caseins and whey proteins. The majority of protein in milk is casein, which in raw milk is found in the form of large colloidal aggregates called micelles, containing
thousands of molecules of the four members of the rheomorphic casein family (s1-, s2-, -
and -casein) and, in a crucial stabilising influence, nanoclusters of colloidal calcium phosphate (CCP). Intermolecular interactions between casein are minimal at ~150 MPa, whereas the solubility of CCP increases with pressure. Primarily, as a result of the solubilisation of CCP, casein micelles are disrupted under pressure. Micellar disruption is more extensive at higher pressure and at lower casein concentration, pH and temperature and, in the presence of calcium-sequestering agents. On holding casein micelles for prolonged times (>10 min) at 200-300 MPa, initial disruption of casein micelles is followed by subsequent reformation of casein particles, probably due to the fact that association of protein as a result of weak cohesive interactions is favoured. This process is more extensive at high temperature, indicating the importance of hydrophobic bonding in the process. When >~75% of CCP is solubilised, reformation of casein particles under pressure does not occur. As a result of changes that occur under pressure, casein micelles in HP-treated system differ considerably from their untreated counterparts, e.g., in size and hydration, as well as their functionality e.g., in cheese, yoghurt and ice cream. The other class of milk proteins, the globular whey proteins, are unfolded under high pressure. The unfolding of beta-lactoglobulin exposes a free sulphydryl group, which can subsequently interact with other cysteine-containing protein though sulphydrlyl-disulphide interchange reactions, e.g., with other whey proteins or with caseins, either in the micellar or non-micellar phase. Interactions of whey proteins with caseins do not affect changes in casein micelles under pressure, but do strongly affect the functionality of casein micelles in HP-treated dairy systems. In this presentation, the state of knowledge of this area developed during the last decade will be reviewed, in the light of the insights gained into how pressure affects protein structure, conformation and properties.
*E-mail : [email protected]
Keywords : casein; high pressure; milk protein; interactions
66
Pasting properties of high pressure treated starch suspensions
H. Simonin, S. Marzouki, C. Guyon, M. Orlowska, A. Le Bail, M. de Lamballerie*
GEPEA, ENITIAA, BP82225, 443222 Nantes cedex 3, France
High pressure (HP) technology offers a new possibility of starch application in food products, for example as fat substitute. In fact, HP is a promising technology to discover novel textures which may retain flavours and nutrients while providing food safety. Most HP gelatinized starches maintain their granular morphology, with very little swelling but rapid retrogadation
[1]. However waxy starches are more pressure sensitive and can show a
complete disintegration of granules after pressurization[2]
. The mechanism of starch gelatinisation during the HP treatment, as well as the properties of starch gels obtained under HP conditions, are still under investigation. In this study the properties of rice and maize waxy starch suspensions were studied after or during HP treatments at 500 MPa. Particularly, the evolution of pasting properties of starches previously suspended in a gel was studied according to the duration of the HP treatment. Pressure treatment of starch (waxy rice, maize and waxy maize) was performed at 500 MPa during 10-20 or 30 minutes using either 10% native starch-water suspensions or 10% native starch-4% pregelatinized wheat starch-water suspensions. These latest suspensions were used to test the rheological properties. It was analysed by performing flow curves of starch suspensions using a stress controlled rheometer. A centrifugation technique was used to examine the degree of swelling of native starch suspensions. A high pressure cell associated with an inverse light microscope was used to carry out in situ observation of 1% native starch-water suspensions along the pressurization time. As expected, waxy rice starch was the more pressure sensitive among studied starches regarding swelling degree of the gel and microscopic structure. After 10 minutes at 500 MPa, the granular structure disappeared totally and the gel obtained reached its maximal viscosity. It was more viscous than the two maize starches suspensions. Both maize starch gels swelled gradually during 30 minutes of pressurization with a slightly higher swelling degree for the waxy starch. Regarding microscopic structure, maize starch granules grew gradually and kept their granular structure even after 100 minutes at 500 MPa. Whereas waxy maize starch granules kept their original form during 5 minutes at 500 MPa, then more and more granules lost their structure to form a continuous gel phase along the treatment. Viscosity of both gels increased gradually during 30 minutes at 500 MPa, but waxy starch gave the more viscous gels. This study shows that HP gelatinization of waxy starch results in a gradual destructuration of granules whereas non-waxy starch shows continuous swelling of granules. Both phenomena lead to a regular increase in viscosity in the starch suspension and can provide a range of viscosity when starch is previously suspended in a gel. Moreover, using non waxy maize starch, it is possible to obtain a multicomponent gel mixture with granule remnant playing the role of a filling agent with ordered structure.
[1] R. Stute, Heilbronn, R.W. Klingler, S. Boguslawski, M.N. Eshtiaghi, D. Knorr, Starch - Starke 48, 399 (1996).
[2] W. Blaszczak, J. Fornal, V.I. Kiseleva, V.P. Yuryev, A.I. Sergeev, J. Sadowska, Carbohydrate Polymers 68, 387 (2007).
*E-mail : [email protected]
Keywords: high pressure, starch, gelatinization
67
Influence of high pressure and elevated temperature on bacterial spores-inactivation mechanisms above 500 MPa
K. Reineke1*, A. Mathys1, V. Heinz2, D. Knorr1 1 Berlin University of Technology, Department of Food Biotechnology and Food Process
Engineering, Koenigin-Luise-Str. 22, D-14195 Berlin, Germany 2German Institute of Food Technology, p.o.box: 1165, D-49601, Quakenbrueck, Germany
A combination of high pressure and elevated temperature enables the possibility to reduce the thermal load of a food product and to retain its quality during sterilization. The inactivation mechanisms of bacterial spores during this process have to be completely known and understood to establish this technology successfully in the food industry. At low pressures in the range of 100-200 MPa and ambient temperatures a spore germination caused by the activation of the germinant receptors is possible, but a part of the whole spore population is still in the dormant state, which could cause foodborne diseases in the processed product. Consequently, higher pressures and temperatures are needed for the sterilization of foods. Applying very high pressure and temperature to spore suspension in buffer systems, phenomena like the dissociation equilibrium shift in the buffer solution, a possible spore agglomeration and the adiabatic heat of compression has to be taken into account. To investigate the effect of all these parameters, inactivation experiments under isothermal and isobaric conditions above 500 MPa and 60 °C with genetic modified Bacillus subtilis spores were performed. Two different strains of spores lacking the germinant receptors and
one of the cortex lytic enzymes (FB114 [ ger3 sleB] and FB115 [ ger3 cwlJ] and its wild type strain (PS832) were treated in ACES buffer solution (0.05 M, pH 7). The three different samples were treated in time in a SITEC-high pressure unit (Type 0101-7000s) with a teflon cylinder as insulation. The temperature was monitored by a dummy sample container at the upper plug of the high pressure vessel. Thermal treatments (100-110 °C) of wild type spores (PS832) in thin glass capillaries were carried out in ACES- and PBS-buffer solution (0.05 M, pH 7) as well as in ringer solution. The initial cell concentration (around 2*108 cells ml-1) and the particle size distribution were measured with a flow particle image analyzer before every high pressure treatment. The FB114 and FB115 spores germinated under atmospheric conditions very poorly (3*10
5
cells ml-1
) caused by the lack of the nutrient germinant receptors. After a pressure treatment at 550 MPa, 37 °C and 5 min more than 8*10
7 cells ml
-1 could be germinated by high pressure.
This results could be explained by a pressure induced opening the dipicolinic acid channels. After a 1 h treatment nearly all spores (1.7*10
8 cells ml
-1) were germinated by high pressure.
An increase of pressures and temperatures results in a strongly increased inactivation of all spore strains. As found previously for Geobacillus stearothermophilus spores, pressure around over 550 MPa and temperatures above 70°C seem to be a promising process window for high pressure thermal sterilization. This research improves the understanding of spore inactivation during high pressure thermal sterilization and strongly indicates pressures and temperatures above 600 MPa and 70 °C as possible process conditions.
* E-mail : [email protected] Keywords : High pressure thermal sterilization, inactivation mechanisms, bacterial spores
68
In situ investigation of the turbulent-laminar transition of temperature fluctuation during the pressure building up to 300 MPa
K. Song*, J. Jovanovic, C. Rauh. A. Delgado
Lehrstuhl für Strömungsmechanik, Friedrich-Alexander Univ. Cauerstr.4 91058 Erlangen, Germany
The investigation of fluid flow under high pressure up to 300 MPa has been developing extensively during recent years[1-4]. The range of applications of high pressure technologies spreads from food processing through chemical, bio-chemical and pharmaceutical applications to mechanical engineering. This results in high demand for experimental data as well as theoretical background of various phenomena occurring in the fluids during high pressure process. Up-to-date research shows that the properties of many substances and the phenomena occurring under increased pressure differ significantly from their properties in ambient conditions. Song et al. showed for the first time that a sudden increase of pressure in liquids can completely re-laminarize the turbulent flow[3-4]. This paper focuses on investigation of the fluctuations in the liquid’s temperature field during the pressure build-up phase. The 1.5 litre pressure autoclave is fed with silicon oil (hexamethyldisiloxane) via a nozzle with a diameter of 1.6 mm. The investigation using High Pressure-Hotwire Anemometry (HP-HWA) concerns the free jet flowing out from the nozzle into the vessel. The pressure of 300 MPa is reached within 52 s, the temperature due to the compression increases from 18 to 60 °C, and the Reynolds number (Re) varies from 10000 to 2000. Initially fully turbulent flow starts to be damped by increasing viscous forces which grow due to the pressure ramp. When viscous forces prevail over fluid’s inertia, the turbulence can break down. The transition in the temperature field from turbulence to laminar occurs at the level of Re≈3600 which is typical for turbulent flows. The results show great regularity in the occurrence of the turbulence break-down due to the increase of viscosity and compressibility effects. The other critical parameters for the turbulence-laminar transition are also obtained. The knowledge gathered in the experiments could be adapted for various fields of industry. For example, in internal combustion engines, it would enable keeping fully laminar flame thus controlling the combustion better and obtaining better efficiency. On the other hand, when the laminarization is undesired, such conditions could be avoided, e.g. in HP-food processing the turbulence in high pressure vessel assured more uniform pasteurization and enzyme inactivation.
[1] M. Pehl, F. Werner, A. Delgado, Experiments in Fluids 29, 302 (2000) [2] P.K. Kitsubun, C. Hartmann, A. Delgado, Proc. Appl. Math. Mech. 5, 573 (2005) [3] K. Song, C. Rauh, A. Delgado, Proc. Appl. Math. Mech. 8, 10603 (2008) [4] K. Song, A. Al-Salaymeh, J. Jovanovic, C.Rauh, A. Delgado, Ann. New York Acad. Sci., vol.
High- Pressure Bioscience and Biotechnology-5th International Conference (submitted)
E-mail : [email protected]
Keywords: high pressure, Hotwire Anemometer, turbulence, transition
69
Rheological properties of biomatter at high pressure measurement techniques and relevance for high pressure processes
L. Kulisiewicz*, C. Rauh, A. Delgado
Institute of Fluid Mechanics, University Erlangen-Nuremberg, Cauerstr. 4, 91058 Erlangen, Germany
Rheological properties belong to basic transport quantities influencing the energy and mass transfer on micro- and macroscale. Furthermore, rheological investigations provide insight into the molecular structure of the substance and into the phenomena governing the microstructural processes. Hence, rheological characterisation is of fundamental importance in engineering and research on processes involving high hydrostatic pressures (up to 1 GPa), such as high pressure food treatment, deep see exploitation, tribology, supercritical fluids techniques and others.
In the present work practically relevant rheological investigations on fluid and also soft solid systems under high pressure are presented and their relevance for high pressure processes is discussed. The investigations on liquids were carried out using a rolling ball viscosimeter developed by Först et al.[1]. In situ measurements reveal typically an exponential increase of dynamic viscosity η of liquids with pressure. Impact of this behaviour on high pressure processes, particularly on distribution of temperature and reaction rate is discussed with use of dimensional analysis of fundamental governing equations of fluid mechanics. Several conclusions of general kind can be made concerning temperature homogeneity in high pressure vessels, development of boundary layer and turbulence. Rheological investigations of soft solids (e.g. protein gels) under high pressure require special approach providing nondestructive measurement. In this work the oscillatory high pressure rheometer developed by Kulisiewicz et al.[2] is used for measurement of the storage modulus and loss tangent of gels. By means of rheological modelling the characteristic parameters of the gel network, i.e. number of junctions per molecular chain and their length is calculated and conclusions on influence of high pressure process parameters on gel-like food commodities are drawn.
[1] P. Först, F. Werner, A. Delgado, Rheol. Acta 39, 566 (2000) [2] L. Kulisiewicz, A. Baars, A. Delgado, Bull. Pol. Acad. Sci.:Tech. Sci. 55, 239 (2007)
*E-mail : [email protected]
Keywords: rheology, viscosity, measurement techniques, gel
70
IgE Binding of Apple Allergens Preserved after Treatments at High Pressure
A. Fernández*1, P. Butz2 and B. Tauscher2 1Institute of Agrochemistry and Food Technology (CSIC), Apdo. Correos 73,
46100 Burjassot, Valencia, Spain 2Max-Rubner Institut, Haid-und-Neustr. 9, 76131 Karlsruhe, Germany
IgE binding capacity of an apple extract (Golden Delicious) after combined pressure/temperature treatments was analysed using pools of sera of Spanish allergic patients. Effects of high pressure on the major protein bands after SDS electrophoresis were tested after transference to nitrocellulose membranes. Additionally, a competitive RAST inhibition was performed with native proteins, and allergen stability was evaluated after 10 months storage. Immunoblots showed that high pressure treatments up to 800 MPa for 10 min and 60 ºC were not able to reduce the IgE binding capacity of the apple extracts. However, high pressure treatments at 80 °C originated a decrease in the capacity of IgE binding of apple extracts assayed by immunoblotting. This effect could not be corroborated by RAST, probably due to pressure/heat resistance of one of the major apple allergens, Mal d1. Generally, the retention of IgE binding capacity of samples kept in the dried state at -18 °C was comparable to fresh extracts, while samples preserved in solution showed a lower IgE binding potential also after pressure/temperature combinations.
Acknowledgements: Project DAAD-INIA; Hospital La Paz (Madrid, Spain), Dr. Miguel Blanca and Javier Álvarez
* E-mail: [email protected]
Keywords: high pressure, IgE binding, RAST, immunoblots
71
Influence of high pressure treatment on allergenicity of rDau c1 and carrot juice demonstrated by in vitro and in vivo tests
M. Heroldova1*, H. Vavrova1, P. Kucera1, I. Setinova2, S. Honzova2, M. Kminkova3, J. Strohalm3, P. Novotna3, A. Proskova3, M. Houska3
1Department of Allergy and Clinical Immunology of the Faculty Hospital Kralovske Vinohrady, Prague, Czech Republic
2Centre of Immunology, Imumed, Prague, Czech Republic 3Food Research Institute Prague, Prague, Czech Republic
The aim of our study was to detect the influence of high pressure treatment (HPT) on allergenicity of recombinant allergen rDau c1 and carrot juice using in vitro and in vivo tests.
The buffer solution of recombinant main carrot allergen r Dau c1 for basophil activation test (BAT) and Western blot (WB) was used. Blood samples from patients with birch pollen allergy and symptoms of oral allergy syndrome (OAS) reacted with rDau c1 in BAT. Dau c1 was pre-treated by pressure 500 MPa for 10 minutes and different temperatures (30, 40, 50°C) and pressure from 400 to 550 MPa for 3 and 10 minutes. Neither the HPT from 400 to 550 MPa for 3 and 10 minutes nor the HPT at 500 MPa for 10 minutes and temperature 30,40 and 50°C had the influence on solution of rDau c1 in BAT. At temperature 30 and 50°C 15 % decrease of basophile activation was found.
In WB method serum samples of birch pollen allergic patients reacted with solution of rDau c1 treated by HP 500 MPa for 10 minutes at temperature 30, 40 and 50°C. This HPT of rDau c1 did not influence the immune reactivity of rDau c1 in WB test.
The structural changes of rDau c1 caused by HPT studied by circular dichroismus CD spectra were found. Mild increase of beta-helical structure was observed. The main changes were seen in rDau c1 samples treated 10 min. at 500 MPa and temperature 50°C.
The influence of HPT on allergenicity of carrot juice was studied. The results of skin prick tests (SPT) and BAT did not show any influence of HPT on allergenicity of carrot juice. Pressure of 500 MPa for 10 minutes and temperature 30, 40 and 50°C did not inactivate allergen Dau c1 in carrot juice in WB. HPT from 450 to 550 MPa for 3 and 10 minutes at temperature 30°C had no influence on immune reactivity of Dau c1 in carrot juice.
19 patients underwent double-blind, placebo-controlled food challenge (DBPCFC). 13 of them had reaction on placebo and were discarded, 1 patient did not react at any material (placebo, HPT material and fresh frozen carrot juice), 3 patients had positive test (reacted on HPT material and non-treated fresh frozen carrot juice) and 2 patients had negative reaction (reacted only on fresh frozen material). In our study we did not confirm the influence of HPT on allergenicity of rDau c1 and carrot juice using in vitro and in vivo tests.
This work was supported by the grant No. 2B06139
*E-mail : [email protected]
Keywords: carrot, Dau c 1, allergen, high pressure
72
Textural properties of fresh cheese made from milk treated by Ultra-High Pressure Homogenisation
A. Zamora, B. Guamis, A.J. Trujillo*
Centre Especial de Recerca Planta de Tecnologia dels Aliments (CERPTA), XaRTA, XiT, MALTA Consolider Group, Departament de Ciència Animal i dels Aliments,
Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
The aim of the study was to evaluate the effect of homogenising milk with Ultra-High Pressure Homogenisation (UHPH) on the textural properties of a starter-free fresh cheese. UHPH (300 MPa at 30ºC) significantly reduced the size of milk particles and improved the coagulation properties by reducing rennet clotting time and increasing optical density of curds compared to pasteurisation (PA; 80ºC for 15 s) and homogenisation-pasteurisation (HP; 18 MPa at 60ºC, 80ºC for 15 s). A sensory panel described UHPH-cheeses as crumbly, grainy and hard. Textural analysis showed that both the Young’s modulus and the stress at fracture of UHPH-cheeses were much higher. However, the strain at fracture of UHPH-cheeses was similar to those of HP-cheeses. In addition, G* of the rheological analysis significantly differed; UHPH-cheeses presented the highest G* followed by HP- and PA-cheeses. Concerning the water content of cheeses, the sensory panel found UHPH-cheeses much drier than HP-cheeses. However, UHPH-cheeses showed slightly higher moisture content compared to HP-cheeses. Both homogenisations, especially UHPH, triggered a change in the typology of water retained by decreasing the amount of water type II. The temperature needed to change from one type to the other was significantly higher in UHPH-cheeses. Forced whey drainage through centrifugation showed that the water-holding capacity of UHPH-cheeses was significantly higher to that of HP- and PA-cheeses. Confocal images revealed that matrices of UHPH-cheeses were tighter with smaller interfacial spaces, thus water would be tightly entrapped in the protein network. In conclusion, UHPH triggered textural changes which were detected by sensory evaluation. Instrumental analysis helped to understand that two phenomena were at the base of the changes: the drastic decrease in size of milk particles would lead to harder and less elastic cheeses, and the change in the water typology and water-binding capacity of the cheese matrix would lead to a drier mouth-feeling.
* E-Mail : [email protected]
Keywords: Ultra-high pressure homogenisation; cheese; microstructure
73
Citrinin Inactivation Model Study by High Hydrostatic Pressure Treated Black Table Olives
H. Alpas*1, Ö. Tokuşoğlu2, F. Bozoğlu1, S. Buzrul1
1 Food Engineering Department, Middle East Technical University, Ankara, Turkey 2 Celal Bayar University, Manisa, Turkey
Black table olives are more consumed breakfast foodstuffs especially in all Mediterranean. Recently, there is an increased risk of citrinin (CIT) mycotoxin in table olives. CIT has a nephrotoxic, genotoxic potential based on in vitro tests and possibly a carcinogenic effect for humans. The inactivation capacity of the spiked citrinin (CIT) in black table olive pastes (Vakum FL) via two temperature and two pressure conditions by high hydrostatic pressure (HHP) process was carried out. Olive pastes were subjected to HHP treatment for 5 minutes at 250 MPa for two temperature values (25±1°C; 35±1°C) whereas at 350 MPa for two temperatures (25±1°C; 35±1°C). HHP treated and control black table olive pastes were analyzed by the isocratic high performance liquid chromatography (HPLC) using fluorescence detection (Ex. 333 nm; Em: 495nm) and 5 μm, ODS2, 4.6mm× 250mm column with the mobil phase mixture of acetonitrile /water / formic acid (60/38/2, v/v/v) (pH 2.5). The proposed weibull model for these four conditions was compared with response surface methodology (RSM) for inactivation of citrinin by HHP. The prediction capabilities of proposed models were acquired.
* E-mail: [email protected] Keywords : Citrinin, HHP, inactivation
74
Allergenicity of main celery allergen rApi g1 and high pressure treatment M. Houska*1, M. Kminkova1, J. Strohalm1, I. Setinova2, M. Heroldova3, P. Novotna1,
S. Honzova2, H. Vavrova3, P. Kucera3, A. Proskova1 1Food Research Institute Prague 2Center of Immunology, Imumed
3Department of Allergology and Clinical Immunology of the Faculty Hospital Kralovske Vinohrady, Prague, Czech Republic
The structural changes and allergenicity of recombinant main celery allergen rApi g1 caused by the high pressure were studied. We have treated the buffer solutions of rApi g1 by high pressure at 500 MPa for pressure holding times 10 and 20 minutes and holding time temperatures 30, 40 and 50°C. The structural changes were studied by circular dichroismus CD spectra. The allergenic reaction of the rApi g1 was tested by the Western blot. The greatest changes of the structure were found at samples treated by 500 MPa at 50°C. The samples treated at this temperature at pressure levels 450, 500 a 550 MPa held for 10 and 20 minutes showed that protein structure changes are positively correlated with pressure. Western blot evidenced that pressure 500 MPa held for 10-20 minutes at temperatures 30-50°C did not change the allergenicity of the rApi g1 protein compared with untreated sample.
Acknowledgement: The authors thank to Dr. Ondrej Julinek IChT Prague for precise analysis of the structure changes by CD dichroismus method. This work was supported by the grant No. 2B06139
*E-mail : [email protected] Keywords: celery, Api g1, allergen, high pressure
75
Thermal diffusivity estimation of mashed potatoes and olive oil at high pressure
A. Landfeld, J. Strohalm, K. Kýhos, K. Hoke, R. Zitny1, M. Houska*
Food Research Institute Prague 1Czech Technical University in Prague Czech Republic
The effect of high pressure on thermal diffusivity of mashed potatoes and olive oil was studied. The sample was placed at Cu cup at high pressure chamber. Nominal pressures were 400 MPa and 500 MPa and temperature ranged 20 – 105°C. The thermal diffusivity was estimated from time-temperature decay during pressure holding time. Temperature was measured at three different positions in the sample (wall, centre and at given radial distance). These data were compared with optimized numerical solution (finite element method). Numerical solution was fit to data by optimization of input thermal diffusivity at initial and final temperatures and for two positions in the sample. Wall temperature data were used as given boundary condition. Thermal diffusivity for both samples grows with temperature. The thermal diffusivity of mashed potatoes increases with pressure and of olive oil decreases with pressure.
*E-mail : [email protected] Keywords: thermal diffusivity, olive oil, mashed potatoes, high pressure
76
Allergenicity of main birch allergen rBet v1 and high pressure treatment
I. Setinova*2, M. Kminkova1, J. Strohalm1, , M. Heroldova3, P. Novotna1, S. Honzova2,
H. Vavrova3, P. Kucera3, A. Proskova1, M. Houska1 1Food Research Institute Prague 2Center of Immunology, Imumed
3Department of Allergology and Clinical Immunology of the Faculty Hospital Kralovske Vinohrady, Prague, Czech Republic
The aim of our study was to find out the influence of the high pressure on the structural changes and allergenicity of recombinant main birch allergen rBet v1. We have treated the buffer solutions of rBet v1 by high pressure in range 450-550 MPa for pressure holding times 10 minutes at temperatures 30-50°C. The structural changes were studied by circular dichroismus CD spectra. The allergenic reaction of the rBet v1 was tested by the Western blot. The greatest changes of the structure were found at samples treated by 450 MPa at 30°C. The samples treated at this temperature at pressure levels 500 and 550 MPa held for 10 minutes did not show any structure changes. The pressure 450 – 550 MPa held for 10 minutes at temperatures 30, 40 and 50 °C did not change the allergenicity of the rBet v1 protein compared with untreated sample in Western Blot method.
Acknowledgement: The authors thank to Dr. Ondrej Julinek IChT Prague for precise analysis of the structure changes by CD dichroismus method. This work was supported by the grant No. 2B06139
*E-mail : [email protected] Keywords: high pressure treatment, allergen Bet v1, birch
77
High hydrostatic pressure effects on lactic acid bacteria (LAB), oleuropein hydrolizing capacity and aerobic mesophilic bacteria of black table olives:
differantions by chemometrics
F. Bozoğlu*1, Ö. Tokuşoğlu2 H. Alpas1 1 Food Engineering Department, Middle East Technical University, Ankara, Turkey
2 Celal Bayar University, Manisa, Turkey
Black table olives are valuable commodity worldwide that are consumed as whole, stuffed or sliced based mainly on International Olive Oil Council (IOOC) directives. The aims of this study were to enumerate lactic acid bacteria (LAB), aerobic mesofilic bacteria (AMB) at naturally fermented black olives produced in two company of olives,Turkey after HHP treatment and to detect lactic acid (LA) and pH levels at control and HHP-treated olives. Each 50 g of HHP treated and control olives via stomacher and was filled to each cryo tubes aseptic microbiological conditions prior to HHP process. Black olive pastes were exposed to HHP application for 5 min at both 250 MPa and 350 MPa for both temperature including 25°C and 35°C. For control and HHP-treated samples; MRS agar medium (Oxoid) with 0.17 g/L of cycloheximide (Sigma), incubated at 30°C for 4 days in anaerobiosis for lactic acid bacteria (LAB) and plate count agar (PCA) incubated at 30±1 °C for 48 h for aerobic mesophilic bacteria (AMB). Oleuropein (OLE) hydrolizing capacity was determined by HPLC. Titratable acidity as lactic acid (LA) and pH value were determined according to the Turkish Standards. The flora contained predominantly Lactobacillus plantarum and also Leuconostoc mesenteroides subsp., Leuconostoc spp. Lactobacilli were enumerated as 9.3×10
1 – 8.4×10
5 cfu/g for control
olives. HHP treatment at 5 min/250 MPa/25 °C not significantly altered the LAB (p<0.01) while treatment at 5 min/350 MPa /35 °C reduced the lactic acid bacterial growth (4.8×10
1-
7.56×104 cfu/g). Hydrolyzing capacity of bitter phenolic OLE was less decreased at 350
MPa/35 °C whereas more decreased at 250 MPa/25 °C for 5 min duration (p<0.01). LA concentration was found as 0.65 - 1.22 mol/L at 5 min/250 MPa/25 °C. Total Aerobic Mesofilic Bacteria were determined as 3.48 - 4.63 log cfu/g at control while < 2.00 log cfu/g after HHP treatment at 5 min at 350 MPa /35 °C which reducing level as 55-96% (p<0.01). The prediction capabilities and differentations of proposed models were acquired.
*1+ Ö.Tokuşoğlu, H.Alpas, F.Bozoğlu, 135-26 Technical Research Paper. 2008 IFT Annual Meeting+Food Expo. 2008, 183, June 28-July 1, New Orleans, LA, USA.
[2]Unified Qualitative Standard Applying to Table
*E-mail : [email protected] Keywords : HHP, LAB, TAMB, Oleuropein
78
The effect of high pressure on selected physiological properties of Lactobacillus species
A. Grześkiewicz*, A. Reps, A. Jankowska, K. Wiśniewska
Chair of Food Biotechnology, Faculty of Food Science, University of Warmia and Mazury, Olsztyn, Poland
Results of the current studies indicate that high pressure can alter the physiological properties of micro-organisms allowing growth in extreme environmental conditions.
The aim of the study was to determine the effect of pressure (30, 60, 90 and 300 MPa/ 1 min/18°C) on survival and growth of selected 6 strains of Lactobacillus acidophilus, 2 Lactobacillus paracasei, 9 Lactobacillus casei and 5 Lactobacillus delbrueckii ssp bulgaricus, in an enviroment with varying concentrations of salts and varying pH.
The number of surviving bacteria was determined before and after pressurization, as the bacteria were grown on MRS at pH 5.4, on MRS with the addition of 2% and 5% NaCl, and on MRS at pH 2 and 4.
The number of CFU was slightly reduced after pressurization at 30, 60 and 90 MPa. Pressurization in the 30-90 MPa range did not affect the intensity of the growth of bacteria in conditions with varying acidity and salt content. In contrast, the pressure 300 MPa resulted in a higher reduction of CFU of the tested strains and weakened the growth of the strains tested at different pH and salt concentrations.
Most examined strains exhibited no growth on MRS, pH 2, regardles whether the cells were pressurized or not.
Significant differences in sensitivity to high pressures were found in bacteria of the same species.
Bacteria of the species Lactobacillus delbrueckii ssp bulgaricus were the most sensitive to high pressure.
*E-mail : [email protected] Keywords: pressurization, Lactobacillus, physiological properties
79
Effect of pressurization on antibacterial properties of Lactobacillus strains
A. Jankowska*, A. Grześkiewicz, K. Wiśniewska, A. Reps
Chair of Food Biotechnology, University of Warmia and Mazury, Olsztyn, Poland
The capability to produce antibacterial substances, including lactic and acetic acid, hydrogen peroxide, diacetyl, reuterine, bacteriocins and a number of others, is a strain-specific characteristic. The antimicrobial activity is also affected by extrinsic factors, i.e. culture medium composition, hydration, aeration, culture age, temperature and incubation time [1,2].
The objective of the study was to determine the effect of high pressures on antibacterial properties of selected strains of the Lactobacillus species.
After 18-h incubation on a liquid MRS medium, cultures of Lactobacillus casei, Lactobacillus delbrueckii ssp. bulgaricus and Lactobactobacillus acidophilus strains were subjected to a high pressure treatment at 30, 60, 90, and 300 MPa/1 min, at a temperature of 18°C. In the non-pressurized and pressurized cultures, the antibacterial activity was determined with a modified well method against test strains of the genus Enterobacteriaceae: Klebsiella pneumoniae, Proteus, Enterobacter cloaceae, and Escherichia coli.
The cultures were additionally assayed for an acidifying activity, capability to produce hydrogen peroxide, and for bacterial count with the plate method. The susceptibility of the bacteria pressurized at 30-90 MPa was diversified and depended on the strain and not on its species affiliation. A pressure of 300 MPa evoked a considerable reduction in the survivability of the strains examined, with strains of the species Lactobacillus delbrueckii ssp. bulgaricus being the most susceptible to the pressure treatment. As compared to pressures of 30-90 MPa, the pressure treatment at 300 MPa caused the inhibition of the acidifying activity of the strains analyzed. In turn, the pressures applied had no impact on the quantity of hydrogen peroxide synthesized. An increase in pressure was accompanied by a diminishing antibacterial activity of the investigated Lactobacillus strains. A pressure of 300 MPa resulted in a considerable reduction in, and even at complete loss of the capability to inhibit the growth of the test bacteria by the analyzed strains of the Lactobacillus species.
[1] M. Arici, B. Bilgin, O. Sagdic, C. Ozdemir, Food Microbiology. 21, 19 (2004). [2] S. P. Voravuthikunchai, S. Bilasoi, O. Supamala, Anaerobe. 12, 221 (2006).
*E-mail : [email protected] Keywords: high pressure, Lactobacillus, antibacterial activity
80
High pressure processing of foods and packaging materials
A. Largeteau1*, I. Angulo2, J.P. Coulet3 and G. Demazeau1 1CNRS, University Bordeaux, ICMCB site ENSCPB, 87 Av. Dr Schweitzer,
Pessac, F-33608, France 2Gaiker Technologival Center – Department of Plastics and Composites –
Parque Technologico Edificio 202, 48170 Zamudio, Spain 3Amcor Flexibles – R D laboratory – BP 45 – Route des Chalais – F-16300 Barbezieux, France
Due to the weak energy conveyed in a liquid phase submitted to high pressure conditions, such a thermodynamical parameter was developed in Biosciences, in particular in two different domains: Food processing [1,2] and Biology[3,4]. High Pressure Processing (HPP) is one of the promising methods for microbiological safety and preservation of the organoleptic properties. Such applications were initiated during the first part of the XX century in particular by P.W Bridgman[5] in US, J and J. Basset in France[6]. In order to prevent the use of aseptic environment, pre-packaging of biological products has been preferentially developed[7, 8].
Packaging must be flexible enough to transfer pressure to the product without break and without change of its physico-chemical properties. Different polymers have been tested for preparing pouches filled with liquid (FSLs) simulating Foods and then treated under HPP. The effect of HPP on mechanical properties (tensile strength and seal strength), permeability (oxygen and water vapor), global migration in different food stimulants (water, acetic acid 3%, ethyl alcohol 10%, iso-octane) have been studied and compared.
In this work, two different packaging films with multilayer PA/PE: VIROFLEXAL PA/PE (20/60μm) coextrusion and RILTHENE PA/PE (20/60 μm) laminated from Amcor Flexibles have been evaluated. These films have been treated at various hydrostatic pressures (P= 400 MPa and 500 MPa) at T= +20°C and P= 200 MPa at T= -20°C for a time of exposure close to 15 min. The physico-chemical characterizations before and after the high pressure treatments were: the tensile strength, the sealing strength, the oxygen barrier, the global migration. If VIROFLEXAL seems to be appropriated for food packaging at ambient temperature conditions (+20°C), on the contrary RILTHENE could be a promising packaging at low temperatures (≈-20°C) for developing HHP in inactivation of pathogens for biological applications.
*1+ R. Hayashi, “Engineering and Food” p.815-826, W.E.L. Spiess and H. Shubert Ed.Vol.2 Elsevier Applied Science (London) (1989)
[2] D. Knorr, 47, 156 (1993) [3] C. Balny, K. Heremans, P. Masson, Biofutur, 112, 37 (1992) [4] Y. Rigaldie, G. Demazeau, Annales Pharmaceutiques Françaises, 62, 116 (2004) [5] P.W. Bridgman, J. Biological Chem. 19, 511 (1914) [6] J. Basset, M. Macheboeuf, C. R. Acad. Sci. 196, 67 (1932) [7] Y. Lambert, G. Demazeau, A. Largeteau, S. Laborde-Croubit, M. Cabannes, J.M. Bouvier,
High Pres. Res. 19, 207 (2000) [8] A. Largeteau, I. Angulo, J.P. Coulet, G. Demazeau, International Conference on High
Pressure Science and Technology. Joint 20th AIRAPT-43rd EHPRG, Karlsruhe: Proceedings on CD-ROM, 2005. ISBN-923704-49-6. 2005, Karlsruhe
*E-mail : [email protected] Keywords: High Pressure Processing, Packaging in HHP Food Science
81
Antibiotic resistance of pressurized strains of the Lactobacillus species
A. Jankowska*, K. Wiśniewska, A. Reps, A. Grześkiewicz
Chair of Food Biotechnology, University of Warmia and Mazury, Olsztyn, Poland
In the case of lactic fermentation bacteria that are often applied in antibiotic therapy, the resistance to antibiotics is a desirable trait because its enables colonizing the human gastrointestinal tract during treatment with antibiotics or immediately after therapy [1].
The study was aimed at determining the impact of higher pressures on the antibiotic resistance of selected strains of the Lactobacillus species.
After incubation for 18 h on a liquid MRS medium, cultures of Lactobacillus casei, Lactobacillus delbrueckii ssp. bulgaricus and Lactobactobacillus acidophilus were subjected to a high pressure treatment at 30, 60, 90, and 300 MPa/1min at a temperature of 18°C. The non-pressurized and pressurized cultures were determined for resistance to antibiotics, including: erythromycin, ampicillin, kanamycin, gentamycin, tetracycline, penicillin, and neomycin, with the disc diffusion method. The concentration of Lactobacillus strain cells in the culture medium reached 10
4-10
5 cfu/ml. In addition, the bacterial count was assayed with
the plate method.
The non-pressurized and pressurized cultures were determined for resistance to antibiotics, including: erythromycin, ampicillin, kanamycin, gentamycin, tetracycline, penicillin, and neomycin, with the disc diffusion method. the concentration of Lactobacillus strain cells in the culture medium reached 10
4-10
5 cfu/ml. In addition, the bacterial count was assayed with the
plate method. The examined strains of Lactobacillus acidophilus displayed the highest susceptibility to ampicillin and erythromycin. Pressurization at 90 MPa evoked an increase in the resistance of the strains examined to antibiotics, whereas a tangible decline in resistance was observed in all investigated strains of Lactobacillus acidophilus pressurized at 300 MPa. Strains of Lactobacilus casei were exhibiting lower susceptibility to kanamycin and erythromycin. For most of the Lactobacilus casei strains examined, the resistance to antibiotics was diminishing along with an increase in the pressure applied. In turn, a slight increase of the antibiotic resistance of Lactobacilus casei T14 strain against most of the antibiotics was observed upon pressure treatments at 30, 60 and 90 MPa. A pressure of 300 MPa caused an increase in the susceptibility to the antibiotics applied. The strain Lactobacillus delbrueckii ssp. bulgaricus 0851 exhibited susceptibility to neomycin already when pressurized at 300 MPa, whereas the strain Lactobacillus delbrueckii ssp. bulgaricus T151 was susceptible to that antibiotic at pressures of 90 and 300 MPa. Pressurization over a pressure range of 30-90 MPa had no significant effect on the survivability of the strains examined. In contrast, a pressure of 300 MPa was found to reduce the number of Lactobacillus strains to a considerable extent.
[1] S.B. Levy, B. Marshall, Nat. Med. Rev. 2004, 10, 122.
*E-mail :[email protected] Keywords: high pressure, Lactobacillus, antibiotic resistance
82
Effects of high pressure on colour and polyphenoloxidase, peroxidase and β-glucosidase activities in the strawberry puree
C. Verret1, P. Ballestra1, D. Zeckler1, A. Largeteau2 G. Demazeau2 and A. El Moueffak1 1Equipe de Recherche Agroalimentaire Périgourdine (ERAP) IUT Périgueux
Université Montesquieu Bordeaux IV site universitaire, 24019 Perigueux cedex, France 2Groupe Hautes Pressions ICMCB-ENSCPB
Université Bordeaux I 131 cours de la libération, 33405 Talence, France.
The strawberry puree was obtained from a new variety, Cilady, provided by the CIREF (Centre Inter-régional de Recherche et d’Expérimentation de la Fraise – Dordogne). This variety presents a characteristic flavour [1], [2], a firm texture and sustained colour, researched qualities by food transformation industries. The attractive red color of strawberry puree is a commercially valued property that is highly degraded due to heat processing. For strawberry puree, anthocyanins are responsible for bright red colour. The main problem is their low stability during storage [3].
The effects of high pressure on three important enzymes involved in colour, polyphenoloxidase (PPO), peroxidase (POD) and β-glucosidase in strawberry puree are studied. Puree samples are pressurised under 300, 400 and 500 MPa for 5, 10, 15 and 20 min at 20°C. After application of pressure, enzymatic activities (A) were measured and compared to untreated puree enzymatic activities (A0). For same conditions, the colour (a, b, L) and anthocyanins are evaluted. The study’s objective is to choose the treament conditions for to stabilize the strawberry puree colour.
[1] M. Navarro, C. Verret, P. Pardon and A. El Moueffak, High Pressure Research 22, 693 (2002).
[2] M. Navarro, C. Verret, P. Pardon and A. El Moueffak, Proceeding of the 2th International Conference on High Pressure Bioscience and Biotechnology 2002, 403.
[3] I. Oey, M. Lille, A. Van Loey and M. Hendrickx, Trends in food Science and technology 19, 320 (2008).
*E-mail : [email protected] Keywords : High pressure, Colour, Alteration enzymes, anthocyanins
83
Determination of the isobaric heat capacity of liquid samples by solution of the heat diffusion equation
M. Wierzbicki*, R. Kościesza, R. M. Siegoczyński
Warsaw University of Technology, Faculty of Physics, ul. Koszykowa 75, 00-662 Warszawa, Poland.
We present a method to determine the isobaric heat capacity of a liquid sample from a single temperature sensor data. The numerical solution of the heat diffusion equation is performed for a particular geometry and thermal diffusivity constants of the pressure chamber. The data from the temperature sensor is used as a heat source for internal boundary conditions. The heat diffusion equation is solved on a square grid in cylindrical coordinates. Temperature gradient is integrated over the working area of the pressure chamber yielding the heat flux. The correction to the heat capacity due to the isobaric condition is calculated from the numerical approximation to the equation-of-state surface in the thermodynamical space. Keywords: isobaric heat capacity, numerical solution of the heat diffusion, oleic acid, heat flux, numerical approximation to the equation-of-state
*E-mail : [email protected]
84
Observations of a high pressure phase creation in oleic acid
R. Kościesza*1,L. Kulisiewicz2, A. Delgado2 1Warsaw University of Technology, Faculty of Physics,
Koszykowa 75, 00- 662 Warszawa Poland 2University Erlangen-Nuremberg, Cauerstr. 4, 91058 Erlangen Germany.
Oleic acid is one of the unsaturated fatty acids, frequently appearing in food products, such as edible fats and oils. A molecule of oleic acid possesses a double carbon bond C=C which is responsible for a transition to a new phase when the pressure is applied. This paper presents results of the optical observations of such transition. The observations were made in two cases: of static p – T conditions and dynamic application of the pressure. Obtained visualization reveals differences in creation of the phase and in its further appearance. Some crystal forms may be recognized. These results are of interest for food engineers due to increasing meaning of high pressure food preservation, nutritionists and medical scientists interested in the matter of the fatty acids. Furthermore, a contribution to understanding the effects of pressure on cellular membranes can be made, since their main components are the lipids.
*E-mail : [email protected] Keywords high pressure phase transition, oleic acid, crystal forms
85
Determination of thermodynamic parameters of oleic acid under high pressure.
M. Wierzbicki, R. Kościesza, D. B. Tefelski, R. M. Siegoczyński*
Warsaw University of Technology, Faculty of Physics, ul. Koszykowa 75, 00-662 Warszawa, Poland.
We present high pressure research of oleic acid. The pVT data from a few compression and decompression cycles was used to determine an approximation to the equation-of-state surface in the thermodynamical space. From this approximation we evaluated termodynamical derivatives of oleic acid such as isothermal compressibility and isobaric expansivity as a function of pressure. The analysis of the pVT diagram can answer the question of order of the phase change induced by the high pressure application. The thermodynamic parameters can be utilized in further calculations, yielding isobaric specific heat of the sample before and after the phase transition.
*E-mail : [email protected] Keywords : isothermal compressibility, isobaric expansivity, isobaric specific heat, approximation to the equation-of-state
86
Raman spectroscopy research of triolein under high pressure
D. B. Tefelski*, C. Jastrzębski, M. Wierzbicki, R. M. Siegoczyński, A. J. Rostocki, K. Wieja, R. Kościesza
Warsaw University of Technology, Faculty of Physics, ul. Koszykowa 75, 00-662 Warszawa, Poland
A high pressure Raman spectroscopy research of triolein has been made. Triolein is a triacylglyceride (TAG) of oleic acid. It is an unsaturated fat, present in natural oils such as olive oil. As a basic food component and as an energy storage molecule it has en essential meaning for food and fuel industry.
To generate pressure in our experiment we used high pressure cylindrical chamber with sapphire windows, presented in [1]. We applied pressure up to 750 MPa. Raman spectrometer in “macro” configuration was utilized, which enabled the laser beam to penetrate through the sapphire windows and focus inside the chamber. Raman spectroscopy gives us information about changes of particle vibrational modes which are connected with structural changes of triolein under a pressure.
Interesting changes in triglycerides C—H stretching region at 2650 – 3100 cm-1
were observed under high pressure. We also observed changes in ester carbonyl (C=O) stretching region 1700 – 1780 cm
-1 and C—C stretching region at 1050 – 1150 cm
-1. The overall luminescence of
the sample decreases under pressure, making possible to set longer spectrum acquisition time and obtain more details of the spectrum. The registered changes suggest that high pressure solid phase of triolein is organized as β – polymorphic as was reported in articles [2,3] (with temperature induced phase transitions). We have shown that Raman spectroscopy in TAGs under pressure reveals useful information about its structural changes.
*1+ R. M. Siegoczyoski, R. Kościesza, D. B. Tefelski, A. Kos, High Pressure Research 29, 61 (2009)
[2] Chikayo Akita, Tatsuya Kawaguchi, Fumitoshi Kaneko, J. Phys. Chem. B 110, 4346 (2006) [3] E. Da Silva and D. Rousseau, Phys. Chem. Chem. Phys. 10, 4606 (2008)
*E-mail : [email protected] Keywords: Raman spectroscopy, triacylglycerols, high pressure, phase transitions
87
The compressibility studies of some vegetable oils up to 1 GPa
A. J. Rostocki*1, D. B. Tefelski1, S. Ptasznik2 1Warsaw University of Technology, Faculty of Physics,
Koszykowa 75, 00-662 Warszawa Poland 2Meat and Fat Research Institute, Jubilerska 4, 04-190 Warszawa Poland
The paper presents compressibility studies of some vegetable oils within the range of 1GPa. The measurement of the volume were done for rapeseed oil, soy oil, sunflower oil and linseed oil at constant temperature. On this basis the modified Tait equation coefficients were evaluated. In case of rapeseed oil, soy oil and sunflower oil the discontinuity of P-V characteristic for phase transition has been observed. The value of Tait coefficients for the pressure above the phase transition suggest that the high pressure phase is solidified. The experiment was conducted with computer based data acquisition system with software written in National Instruments LabVIEWTM graphical programming language. Piston displacement was measured by electronic digital calliper with RS232 interface.
*E-mail : [email protected] Keywords: compressibility, vegetable oils, Tait equation
88
Pressure-induced changes in electronic absorption spectrum in oleic acid
K. Wieja*, R. Tarakowski, R.M. Siegoczyński, A.J. Rostocki
Warsaw University of Technology, Faculty of Physics, Koszykowa 75 00-662 Warsaw, Poland
Small absorption of light has been observed in the visible region of spectrum in oleic acid. The strong increase of the absorption was observed in the near ultraviolet region. The increase of absorption in the visible region after the application of pressure has been observed using the apparatus constructed in our lab. A bit of Rhodamine 6G [C28H31N2O3Cl] has been added to oleic acid [C18H34O2] and the examination of a mixture showed the reshaping of the absorption chart as a function of light wavelength. Pressure induced changes of the VIS absorption spectrum in mixture of Rhodamine 6G and oleic acid have been observed comparing to the absorption spectrum of mixture of Rhodamine 6G in ethanol. The analysis of absorption bands of mixtures Rhodamine 6G in ethanol and Rhodamine 6G in oleic acid has been approximated sum of Gaussian curves. The analyses of these absorption charts have been showed that probably VIS absorption of mixture Rhodamine 6G in oleic acid is result of imposition of the absorption spectrum of Rhodamine 6G and to be formed charge transfer complexes.
*E-mail : [email protected] Keywords: Absorption, Rhodamine 6G, Oleic acid, High pressure
89
High pressure inactivation of Pseudomonas in black truffle. Comparison with Pseudomonas fluorescens in tryptone soya broth
P .Ballestra1, C. Verret1, C. Cruz1, A. Largeteau2, G. Demazeau2 and A. El Moueffak1 1Equipe de Recherche Agroalimentaire Périgourdine (ERAP) IUT Périgueux
Université Montesquieu Bordeaux IV site universitaire, 24019 Perigueux cedex, France 2Groupe Hautes Pressions ICMCB-ENSCPB Université Bordeaux I 131 cours de la libération,
33405 Talence, France.
Pseudomonas is one of the most common genera in black Perigord truffle [1]. Its inactivation by high pressures (100-500 MPa / 10 min) applied on truffles at sub-zero or low temperatures (-18°C, 4°C or 20°C) was studied and compared with those of Pseudomonas fluorescens in tryptone soya broth.
Pressurization of truffles at 300 MPa/4°C reduced the bacterial count of Pseudomonas by 5.5 log cycles. Higher pressures, 400 or 500 MPa, at 4 or 20°C, allowed to slightly increase the level of destruction to the value of 6.5 log cycles but did not permit to completely inactivate Pseudomonas. The results showed a residual charge of about 10 CFU/g.
Pressure-shift freezing of truffles, which consists in applying a pressure of 200 MPa/–18°C for 10 min and then in releasing quickly this pressure to induce freezing, reduced the population of Pseudomonas by 3.5 log cycles. The level of inactivation was higher than those obtained with a classical freezing [1].
The application of high pressures on suspensions of Pseudomonas fluorescens in tryptone soya broth induced more extensive reductions. For example, pressurization of suspensions at 300 MPa/4°C or 200 MPa/-18°C (pressure-shift freezing) led to a complete inactivation of P. fluorescens population. At 4 or 20°C, the level of inactivation increased with pressure (100-300 MPa). At 200 MPa, it decreased as the pressurization temperature increased.
Endogenous Pseudomonas in truffle was shown to be more resistant to high pressure treatments than P. fluorescens used for inoculation of broths. Even if some species of endogenous Pseudomonas may be naturally more resistant to pressure than P. fluorescens, it can be supposed that truffles exert a protective effect on endogenous Pseudomonas at the time of pressurization, more particularly at sub-zero temperature.
[1] P. Ballestra, C. Verret, C. Cruz, A. Largeteau, G. Demazeau and A. El Moueffak, Poster, High Pressure Science and Technology, AIRAPT 19th - 41th EHPRG, Bordeaux, 2003.
*E-mail : [email protected] Keywords : High pressure, Truffle, Inactivation, Pseudomonas fluorescens, Pseudomonas.
90
Submicron emulsions processed by ultra-high pressure homogenisation
D. Chevalier-Lucia*, M. Cortés-Muñoz and E. Dumay
Université Montpellier 2, UMR Ingénierie des Agropolymères et Technologies Emergentes, 34095 Montpellier, France
Effects of dynamic high pressure (or ultra-high pressure homogenisation, UHPH) of protein dispersions and protein-stabilised emulsions have been recently studied, using a high pressure homogeniser equipped with a high pressure (HP) valve immediately followed by cooling heat exchangers [1-4]. Model O/W emulsions at pH 6.3, and containing (w/w) 4.3% whey proteins plus 15-45% peanut oil were processed by UHPH at a pre-emulsion temperature of 24°C. Pressure and temperature measured at the inlet and the immediate outlet of the HP valve permitted to evaluate mechanical and thermal energies involved in the process, as respectively calculated from the pressure drop and the short-life temperature increase of the fluid recorded when passing through the HP valve. The effect of oil content, homogenisation pressure (100-300 MPa) or recycling (up to 3 homogenisation passes through the HP valve) at 200 MPa was investigated on the oil droplet size distribution, size indices and viscosity. Increase in homogenisation pressure decreased the droplet size leading to submicron emulsions at pressure ≥ 200 MPa. Monomodal distributions in the nano-scale range were achieved by emulsion recycling at 200 MPa. Rheological behaviour of emulsions varied as a function of the oil droplet size and the oil volume fraction.
[1] M. Cortés-Muñoz, D. Chevalier-Lucia, E. Dumay, Food Hydrocolloids 23, 640 (2009). [2] A. Grácia-Juliá, M. René, M. Cortés-Muñoz, L. Picart, T. Lόpez-Pedemonte, D. Chevalier,
E. Dumay, Food Hydrocolloids 22, 1014 (2008). [3] L. Picart, M. Thiebaud, M. René, J. P. Guiraud, J. C. Cheftel, E. Dumay, Journal of Dairy
Research 73, 454 (2006). [4] M. Thiebaud, E. Dumay, L. Picart, J. P. Guiraud, J. C. Cheftel, International Dairy Journal 13,
427 (2003).
*E-mail : [email protected] Keywords: Ultra-high pressure homogenisation, Dynamic high pressure, Submicron emulsions, Whey proteins
91
Cell cultures as a biological tool to study effects of high-pressure processing on food components
A. Benzaria1*, M. René-Trouillefou1, B. Caporiccio2 and E. Dumay1 1Université Montpellier 2, UMR Ingénierie des Agropolymères et Technologies Emergentes,
F-34095 Montpellier, France 2Université Montpellier 2, UMR Prévention des Malnutritions et Pathologies Associées,
Equipe de Nutrition, F-34095 Montpellier, France
Biological indicators for food processing were studied with a view to characterise the effects of high pressure processing on model proteins such as microorganism enterotoxin or dairy proteins. Cell-toxicity using Caco-2 cells[1], toxin superantigenicity as assessed by T-cell proliferation[2] or protein immunoreactivity evaluated by antibody binding have been studied to complete usual physico-chemical[3] or biophysical determinations. The behaviour of processed proteins on cell monolayers was investigated by assessing the amount of transported proteins through the cells and by confocal microscopy imaging. Combining biological and physico-chemical tools brings new insights in the domain of pressure-induced effects on food components.
[1] M. Maresca, E. Dumay, J. Fantini, B. Caporiccio, Microbes and Infection 9, 1507 (2007). [2] A. Benzaria, N. Meskini, M. Dubois, M. Croset, G. Nemoz, M. Lagarde, A. F. Prigent,
Nutrition 22, 628 (2006). [3] A. Grácia-Juliá, M. René, M. Cortés-Muñoz, L. Picart, T. Lόpez-Pedemonte, D. Chevalier, E.
Dumay, Food Hydrocolloids 22, 1014 (2008).
* E-mail : [email protected] Key-words: High pressure, Enterotoxin, Protein aggregates, T-cell proliferation, Cell cultures
92
Inactivation of Mycobacterium smegmatis in skimmed and whole milk by means of high hydrostatic pressure
R.M. Velazquez-Estrada, M.M. Hernandez-Herrero, T.J. López-Pedemonte, B. Guamis-López and A.X. Roig-Sagués*
Centre Especial de Recerca-Planta de Tecnologia dels Aliments (CERPTA), Departament de Ciència Animal i dels Aliments, Facultat de Veterinària, edifici V,
Universitat Autònoma de Barcelona, 08193, Bellaterra (Barcelona), Spain
Three strains of Mycobacterium smegmatis (CECT 3017, 3020 and 3032) were inoculated at an approximate load of 6.5 log CFU/ml into sterilized skimmed and whole milk to evaluate inactivation by high hydrostatic pressure. Milk samples were stabilized at the required temperature (6°C) and then immediately subjected to 10 min of HHP treatment at 300, 400, or 500 MPa. Viable and injured bacterial counts were obtained by means of a differential plating method using Tryptone Soy Agar enriched with yeast extract (TSAYE) and the same medium with salt (TSAYE+NaCl). Samples were analyzed 2 hours after applying the pressure treatments and after 5 and 8 days of storage at 4°C. Lethality was calculated as the difference between the logarithms of colony counts of the untreated and treated samples (log No- log N). Lethality of Mycobacterium smegmatis increased with the pressure of the treatment until achieving the maximum at 500 MPa. Sub-lethally injured cells were only observed after 400 MPa. Counts in control and pressurized samples did not vary during the subsequent cold storage at 4ºC. Not significant differences were observed between strains. Differences were neither observed between skimmed and whole milk.
*E-mail : [email protected] Mycobacterium, High Hydrostatic Pressure, milk
93
Pressure unfolding of the apple main allergen Mal d1. An in situ high pressure FTIR study
L. Smeller
Dept. Biophysics and Radiation Biology, Semmelweis University, Budapest
Allergy is a disease with growing prevalence. One type of the allergy is caused by foods or food products. Mal d1 is the main allergen found in apple, which can trigger very serious reactions in allergenic patients.
High pressure treatment has been used for a long time to increase food quality and shelf life. Analogous to this treatment of food application of high pressure was suggested to eliminate the allergen activity of apple juices
[1]. Recently however a systematic study on allergen activity
of the main apple allergen Mal d1 demonstrated the lack of the decrease in the allergen activity after pressure treatment up to 500 MPa
[2].
Our aim was to investigate whether the pressure treatment in this range can unfold the protein. All the previous studies were done after the pressure treatment, while our approach the FTIR spectroscopy can provide information about the secondary structure
[3] of the
allergen under pressure (in situ).
Our results show a clear change in the secondary structure, which is reflected in the position of the amide I band of the infrared spectrum, which shifted from 1636 cm
-1 to 1642 cm
-1 upon
application of pressure. The first is characteristic for the beta structure, while the latter for the unfolded one. A simultaneous broadening of the amide I band supports the denaturation of the allergen. The middle point of the transition is at 250 MPa. The conformational transition was not reversible.
It seems that our results are contradictory to those which show no effect on the allergenicity. At the present we cannot have any explanation for the discrepancy. Our efforts are focused on clarifying the environmental factors which could lead to stabilization of the protein.
Acknowledgement: Recombinant Mal d1 was kindly provided by allergology centre Imumed Ltd. Prague, Czech Republic
[1] R. Meyer-Pittroff, H. Behrendt, and J. Ring, High Pressure Res. 27, 63 (2007). [2] Milan Houska, Martina Heroldova, Helena Vavrova, Petr Kucera, Ivana Setinova, Marie
Havranova, Stanislava Honzova, Jan Strohalm, Milena Kminkova, Alexandra Proskova and Pavla Novotna, High Pressure Res., 29, 14 (2009).
[3] Smeller, L., Biochim. Biophys. Acta - Protein Struct. Molec. Enzymol. 1595, 11 (2002).
*E-mail : [email protected] Keywords Allergen Mal d1, FTIR, Unfolding, Protein
94
High pressure treatment of marinated poultry products to improve shelf life and modify meat structure
F. Tintchev, S. Toepfl, U. Bindrich and V. Heinz
German Institute of Food Technologies, Prof.-von-Klitzing-Str. 7, D-49610 Quakenbrueck, Germany
Application of high pressure provides an unique potential for decontamination of fresh, heat sensitive products. The applicability in the final pack as well as the low energy requirements are major advantages in comparison to conventional, thermal processing.
The aim of the project is focussed on prolongation of shelf life of fresh, marinated poultry products by application of high hydrostatic pressure treatment. By selection of suitable processing parameters and marinade formulation shelf life increase and product safety improvement was studied while minimizing undesired changes in sensorial and physical product quality. The impact of the pH value or the salt and phosphate content - which can be varied by using marinades - on microbial decontamination and changes in product properties have been systematically investigated.
Shelf life of marinated turkey meat was determined by analysis of total microbial count, lactic acid bacteria, Enterobacteriaceae spp. and Pseudomonas spp.. The impact on marinade pH on product structural and sensory properties was studied by evaluation of shear force, drip loss and colour parameters.
Microbiological analysis during storage over four weeks showed that microbial count of the HP- treated samples was comparable to fresh ones. Total microbial count, Enterobacteriaceae spp. and Pseudomonas spp of untreated samples reached contamination of above 10
7 cfu/g
already after two weeks of storage.
Generally turkey structure was positively affected after marinating which was expressed in a softer and juicier meat matrix. Significant correlation between pH-value and textural properties of the HP- treated marinated turkey meat was found. Higher pH values affected the meat structure properties and colour parameters positively and reduced high pressure sensibility. Improved water holding capacity and shear force decrease after high pressure treatment of the alkaline marinated Samples was observed. Furthermore a reduction of unwanted colour changes of the basis samples compared to the neutral and acidified samples was found.
In summary marinating poultry meat can improve structural and sensorial properties resulted after high pressure treatment due to a complex mechanism of many biochemical and physical processes. Studying it a great potential to modify and generate desired structure and minimize the negative influence of the high pressure could result. Furthermore a great advantage for the poultry industry could be achieved prolonging the storage time of poultry meat to more than 30 days, an 15 days increase of distribution time than the standard storage.
Email : [email protected] Keywords: marinated poultry meat, high pressure, shelf life, modified meat structure
95
Effect of combined high pressure–temperature treatments with different pressurization gradients and NaCl content on the texture of sausage batter
F. Tintchev, S. Toepfl, U. Bindrich and V. Heinz
German Institute of Food Technologies, Prof.-von-Klitzing-Str. 7, D-49610 Quakenbrueck, Germany
The combined use of pressure and temperature offers promising possibilities for novel textural characteristics of meat sausages. It is known that high pressure- temperature treatments at different holding times affect the processes of myofibrillar tissue disintegration, denaturation, protein solubilisation and gelatinization, which leads to rheological effects resulting in changes in firmness, microstructure and water holding capacity (WHC).
Sausage batter is a poly-dispersed system with visco-elastic behaviour. After heating to 70°C it builds through denaturation an internal protein network with immobilized fat and water converting them into a solid state. The aim of this study was to investigate the mechanism of batter structure modification based on combinations of high pressure/temperature treatments for different holding times and different NaCl/phosphate contents as an alternative to common sausage processing, using lower temperatures and reduced NaCl content.
Sausage batter was treated at 0-600 MPa and 0-50 °C at different holding times. Samples were analyzed by scanning electron microscopy (SEM), drip loss, cook loss, oscillation test and SDS-PAGE. Batter protein solubilisation at low pressures of 100-300 MPa as a function of different holding times, temperatures and NaCl concentrations was investigated.
A significant influence of the pressurization gradient (PG) on the batter structure was found. Samples treated with 2,5 MPa/s were softer and with weaker WHC than these treated with higher PG (40 MPa/s). To evaluate the impact of PG, SEM investigations were done. The dependency on the pressure build- up time were visualized showing that low PG of 2,5 MPa/s form a secondary network. It was caused by soluble proteins which migrate into the serum phase at lower pressures (100-300 MPa) and denaturate there at higher pressures (500-600 MPa) and tempearatures. This parallel matrix was observed to overlay the main matrix increasing its contact area with the water and the fat particles, which results in better WHC and firmness increase. The optimal protein migration (solubilisation) was found at 300 MPa, depending on NaCl content, holding time and temperature.
Organoleprical tests of samples done according to the common recipe showed a significant salty taste after high pressure treatment. Therefore rheological analysis of samples with reduced NaCl content in the range of 0.5- 1% was performed. The samples with 1% NaCl were found to be firmer and with better WHC compared to these with 2 % NaCl.
Combined high pressure/temperature treatments present a huge potential for meat batter modification possibilities including NaCl reduction, as well as structure formation and inactivation in one process step.
Email : [email protected] Keywords: pork batter, high pressure treatment, structure modification, reduced NaCl
96
97
Biosciences
Lectures Mechanical properties of amyloid fibrils from x-ray diffraction experiments in
the diamond anvil cell ______________________________________________ 99
Non denaturating pressure effect on protein-water dynamics and structure ________ 100
Structure-function study of tetrameric urate oxidase studied with fluorescent
spectroscopy, SAXS and X-ray crystallography under high hydrostatic
pressure. ________________________________________________________ 101
Isothermal compressibility of macromolecular crystals and macromolecules: the
case of Cu,Zn superoxide dismutase protein. ___________________________ 102
Kinetic Methods under High Pressure are Helpful for Understanding Protein
Reaction Mechanisms _____________________________________________ 103
The Kinetics and Mechanisms of Pressure-Jump Induced Phase Transitions of
Lyotropic Lipid Mesophases _________________________________________ 104
Role of High Pressure and various factors on the inactivation of pathogens in
biological media __________________________________________________ 105
Pressure Effects on the morphology and migration of mammalian cells ____________ 106
Posters BS 01 : Impact of the composition of the biological medium on pressure
inactivation of micro-organisms._____________________________________ 107
BS 02 : Relationship between the volume properties and pressure stability of
helical rich proteins _______________________________________________ 108
BS 03 : Investigation of L-histidine.HCl.H2O crystals by Raman spectroscopy
under high pressure conditions ______________________________________ 109
BS 04 : High pressure vibrational properties of L-isoleucine crystals _______________ 110
BS 05 : High pressure vibrational properties of L-proline _________________________ 111
BS 06 : Role of the metastable states in the sequential character of the
aggregation of the pressure treated lysozyme _________________________ 112
BS 07 : Thermodynamics of the pressure unfolding of phosphoglycerate kinase _____ 113
98
99
Mechanical properties of amyloid fibrils from x-ray diffraction experiments in the diamond anvil cell
F. Meersman1,2,*, R. Quesada Cabrera2, P.F. McMillan2 & V. Dmitriev3 1Department of Chemistry, Katholieke Universiteit Leuven, B-3001 Leuven, Belgium
2Department of Chemistry, University College London, London, United Kingdom 3Swiss-Norwegian Beam Lines at ESRF, Grenoble, France
Amyloid fibrils are fibrous structures that originate from the self-assembly of polypeptides. Their formation is linked to debilitating diseases associated with protein misfolding including Alzheimer’s and type II diabetes and to prion diseases such as vCJD *1+. In recent years, it has been suggested that such protein and polypeptide fibrils might provide useful novel nanomaterials, for instance as scaffolding to support conducting nanowires [2,3]. Among their interesting properties is their high resistance to chemical and physical perturbations including heat and pressure[4]. A recent analysis of the mechanical properties of insulin fibrils revealed that they possess high strength and stiffness comparable to steel or silk [5].
Here we present the results of a study on the high pressure stability and compressibility of mature amyloid fibrils of insulin and the transthyretin 105-115 (TTR105-115) peptide. These fibrils were investigated by synchrotron x-ray diffraction in a diamond anvil cell using aqueous solution or in silicone oil as pressure-transmitting media. The diffraction results allow a direct estimation of the compression of the cross-β structure, yielding a bulk modulus of ~7-10 GPa, depending on the pressure-transmitting medium. In structural terms the findings provide independent evidence for some recent structural models of amyloid fibrils, and also show how water interacts with the peptide backbone in the fibrillar structure.
[1] Chiti, F. & Dobson, C.M. Annu. Rev. Biochem. 75, 333-366 (2006). [2] Scheibel, T. et al. Proc. Natl. Acad. Sci. USA 100, 4527-4532 (2003). [3] Baldwin, A.J. et al. J. Am. Chem. Soc. 128, 2162-2163 (2006). [4] Meersman, F. & Dobson, C.M. Biochim. Biophys. Acta 1764, 452-460 (2006). [5] Smith, J.F. et al. Proc. Natl. Acad. Sci. USA 103, 15806-15811 (2006).
*E-mail : [email protected]
100
Non denaturating pressure effect on protein-water dynamics and structure
M. G. Ortore1*, , A. Paciaroni2, F. Spinozzi1, P. Mariani1, H. Amenitsch3, J. Ollivier 4 , L. Barbosa1 and D. Russo *
Dipartimento SAIFET, Sezione Scienze Fisiche, Università Politecnica delle Marche and CNISM, Ancona (Italy)
Dipartimento di Fisica, Università degli Studi di Perugia and CNISM, Perugia (Italy) ELETTRA Snchrotron, Trieste( Italy)
4Institut Laue-Langevin (FR)5CNR-INFM & CRS-SOFT c/o Institut Laue-Langevin (FR)
Small angle X-ray scattering and elastic and quasielastic neutron scattering experiments are used to investigate the changes of protein-protein interactions, low resolution structure and internal dynamics of henn egg-white lysozyme as a function of pressure up to 2000 bar. We find that increasing the pressure up to 1500 bar lysozyme completely maintains its globular structure and that the only effect due to pressure can be traced in modifications in the attractive potential between molecules. However, global and local protein dynamics changes at a threshold pressure. We observe an excess variation of the diffusion coefficient compared to water viscosity, likely arising from a change on the hydration water features. We also probe a clear evolution of the internal protein dynamics from diffusing to more localized motions. A new solvent configuration of the first hydration layer could be the origin of the observed local mobility change. Therefore, even small volume changes of hydration water configuration could be reflected through a significant change of protein mean square fluctuations. We discuss the pressure structure and dynamics results in the context of protein-water interface and hydration water dynamics.
* E-mail: [email protected] , [email protected]
101
Structure-function study of tetrameric urate oxidase studied with fluorescent spectroscopy, SAXS and X-ray crystallography
under high hydrostatic pressure.
E. Girard*1,2, S. Marchal3, J. Perez2, S. Finet4, R. Kahn1, R. Fourme2, G. Marassio5, A.C. Dhaussy6, T. Prangé7, M. Giffard8, F. Dulin5, F. Bonneté8, R. Lange3, J.H. Abraini5,
M. Mezouar9, and N. Colloc’h5 1Institut de Biologie Structurale J.-P. Ebel, UMR5075 CEA-CNRS-UJF, 41 rue Jules Horowitz,
38027 Grenoble cedex, France 2Synchrotron-SOLEIL, BP48 Saint Aubin, 91192 Gif sur Yvette, France
3INSERM, U710, Place Eugène Bataillon, 34095 Montpellier, France; Univ. Montpellier 2, 34095 Montpellier, France
4PBSF, FRE 2852–CNRS–Univ. Paris 6, 7 quai Saint Bernard, 75252 Paris, France 5CI-NAPS, UMR6232–UCBN–CNRS, Centre CYCERON, bd Becquerel, 14704 Caen, France
6CRISTMAT ENSICAEN, bd Maréchal Juin, 14000 Caen, France 7LCRB, UMR 8015-Univ. Paris 5 -CNRS, 4 avenue de l’Observatoire, 75270 Paris, France
8CINaM, CNRS UPR 3118, Campus de Luminy, case 913, 13288 Marseille cedex 9, France 9ESRF, BP220, 38027 Grenoble, France
Urate oxidase is a homotetrameric enzyme which has its active sites located at interfaces between sub-units. The enzyme activity is then directly related to the integrity of the tetramer. To study the pressure-induced structural and functional modifications of the enzyme, we use three complementary biophysical techniques under high hydrostatic pressure: fluorescent spectroscopy, SAXS and X-ray crystallography. Activity measurements under pressure and after decompression of pressure-incubated protein were also performed.
Above a pressure of around 200 MPa, the tetramer was irreversibly dissociated into monomers, prior to aggregation. The presence of a ligand in each active site stabilized the tetramer against pressure.
A global model consistent with all experimental results is proposed. The first effect of pressure is to perturb the tetramer making it less active. At higher pressure, the active site is sufficiently perturbed to make the ligand leave its binding pocket. Analysis of the X-ray structure at 150 MPa shows slightly longer distances between the ligand and the protein, which can be interpreted as the premices of ligand departure.
In the structure under pressure, the volume of a large hydrophobic cavity located close to the active site is diminished while the volume of the active site pocket is increased. A high energy conformer, with a larger active site ready to accommodate the substrate and especially the large non-planar product of the enzymatic reaction, may have been trapped by pressure. Combined to the enzyme activity measurements, this X-ray structure evidenced the role of the hydrophobic cavity in the catalytic mechanism of urate oxidase.
*E-mail : [email protected] Keywords: Urate oxidase, pressure-induced dissociation, enzymatic activity, high-energy conformers
102
Isothermal compressibility of macromolecular crystals and macromolecules: the case of Cu,Zn superoxide dismutase protein.
I. Ascone*1, E. Girard2, R. Kahn2, A.C. Dhaussy3, T. Prangé4 and R. Fourme1
1Synchrotron-Soleil, BP48 Saint Aubin, 91192 Gif sur Yvette, France 2IBS, 41 rue Jules Horowitz, 38027 Grenoble, France
3CRISMAT, Ensicaen, 6 Boulevard du Maréchal Juin, 14000 Caen, France 4LCRB, UMR 8015-Univ. Paris 5-CNRS, 4 avenue de l’Observatoire, 75270 Paris, France
We report a new approach [1] for determining the crystal and molecular compressibility in the case of macromolecules using high-pressure macromolecular crystallography (HPMX) [2].
Calculations require the accurate measure of unit-cell parameters as a function of pressure and the crystal structures refined at high pressure. Molecular volumes determined by HPMX also allowed to study the compressibility of the solvent phase in crystals. This approach has been used for the calculation of the intrinsic compressibility, and its variation as a function of pressure, for both an A-DNA octanucleotide, d(GGTATACC)2 and of a globular protein, hen egg-white lysozyme (HEWL) [3] Similarly, albeit less complete, information was obtained on bovine erythrocyte Cu,Zn superoxide dismutase (CuZnSOD), and a B-DNA dodecamer. In the case of orthorhombic CuZnSOD crystals, a low apparent compressibility of crystals has been obtained. This result is discussed in terms of a strong decrease of solvent compressibility in the crystalline environment and of a pressure-dependent solvent intake in the crystal unit-cell.
[1] I. Ascone, E. Girard, R. Kahn, A.C. Dhaussy, T. Prangé and R. Fourme (2009) in preparation. [2] Fourme R., Girard E., Kahn R., Dhaussy A.-C., Ascone I. Annual review of biophysics 38,
153-71 (2009) [3] Fourme, R., Kahn, R., Mezouar, M., Girard, E., Hoerentrup, C., Prange, T. & Ascone, I. J
Synchrotron Radiat 8, 1149 (2001).
*E-mail : [email protected] Keywords: compressibility, high-pressure macromolecular crystallography, Cu,Zn superoxide dismutase protein
103
Kinetic methods under high pressure are helpful for understanding protein reaction mechanisms
S. Marchal1, J. Torrent1, M. Vilanova2, R. Phillips3, A. Munro4, N. Colloc’h5, R. Lange*1 1INSERM U710, Montpellier, France
2Universitat de Girona, Girona, Spain 3University of Georgia, Athens, USA
4University of Strathclyde, Glasgow, Scotland 5UMR 6232-CNRS, Centre Cyceron, Caen, France
Here we are reviewing high pressure stopped-flow (HPSF) and pressure-jump methods for analyzing enzyme reactions and protein folding/unfolding kinetics. Depending on the type of the involved chemical interactions, elementary steps of enzyme reactions are either accelerated or decelerated by pressure. In some cases, this property can be used to change the rate-limiting step of a complex reaction. Hence, individual reaction steps may be revealed which are hidden under atmospheric pressure. We used this approach to study the reaction mechanisms of ligand binding to nitric oxide synthase and cytochrome P450
[1], of the open-
closed allosteric transition of tryptophan synthase[2,3]
, and of the activity of urate oxidase.
For studying protein folding/unfolding we chose ribonuclease A as model. Its folding and unfolding was induced by downward and upward pressure-jumps of small amplitude (40 MPa) in a range from atmospheric pressure up to 600 MPa. Analysis of the activation volumes indicated different possible reaction paths
[4-6]. These paths were found to depend strongly on
specific amino acid residues belonging to the protein chain folding initiation site.
[1] Marchal, H.M. Girvan, A.C.F. Gorren, B. Mayer, A.W. Munro, C. Balny, R. Lange, Biophys. J. 85, 3303 (2003).
[2] R.S. Phillips, E.W. Miles, P. McPhie, S. Marchal, C. Georges, Y. Dupont, R. Lange, J. Am. Chem. Soc. 130, 13580 (2008).
[3] S. Marchal, J. Font, M. Ribo, M. Vilanova, R. Phillips, R. Lange, J. Torrent, Acc. Chem. Res. 2009, in press.
[4] J. Font, J. Torrent, M. Ribo, D.V. Laurents, C. Balny, M. Vilanova, R. Lange, Biophys. J. 91, 2264 (2006).
[5] J. Font, A. Benito, R. Lange, M. Ribó, M. Vilanova, Protein Sci. 15, 1 (2006). [6] J. Torrent, S. Marchal, M. Ribo, M. Vilanova, C. Georges, Y. Dupont, R. Lange, Biophys J. 94,
4056 (2008).
* E-mail: [email protected] Keywords : Stopped-flow, pressure-jump, enzyme activity, protein folding
104
The kinetics and mechanisms of pressure-jump induced phase transitions of lyotropic lipid mesophases
C. Jeworrek* and R. Winter
Department of Chemistry, Physical Chemistry I – Biophysical Chemistry, TU Dortmund, Otto-Hahn-Str. 6, D-44227 Dortmund, Germany
Lipid bilayers, which provide valuable model systems for biomembranes, display a variety of polymorphic phases, depending on their molecular structure and environmental conditions, such as pH, ionic strength, temperature and pressure. By using calorimetric, spectroscopic and diffraction techniques, the temperature and pressure dependent structure and phase behavior of one- and two-component lipid systems, differing in chain configuration and headgroup structure, have been studied in recent years[1-4], but only little is known about their kinetic and non-equilibrium behavior. The pressure-jump relaxation technique in combination with timeresolved small angle X-ray scattering measurements (TRSAXS) is a powerful tool to investigate the kinetics of processes in biological samples, like phase transitions in lipid membranes, the folding/unfolding reaction of proteins as well as the interaction of proteins with membranes. The pressure-jump relaxation technique has several advantages: pressure propagates rapidly so that sample homogeneity is less of a problem, pressure-jumps can be performed bidirectionally, that is, in the pressurization and depressurization directions, and the amplitude of the pressure-jump can be easily and repeatedly varied to a level of high accuracy.
Here, we present data on structural and kinetic aspects of two different lipid systems investigated by the pressure-jump relaxation technique in combination using time-resolved synchrotron SAXS methodology. The three-component lipid bilayer system DOPC:DPPC:cholesterol 1:2:1, which serves as a canonical model raft mixture taking into account the heterogeneity of natural membranes, shows several lamellar-to-lamellar lipid bilayer phase transitions in the temperature range from 10 to 65 oC at pressures ranging from ambient pressure up to 3 kbar (300 MPa). Transitions in both the forward and reverse directions have been measured revealing the transition kinetics between ordered, disordered and heterogeneous lipid bilayer phases[5].The other lipid system, DMPC:DHPC 3.2:1, which forms magnetically alignable bicellar structures, is often used for high pressure NMR studies of proteins. At low temperatures, the system forms bicelles. Upon increasing the temperature, a transition to a nematic phase is observed which gives way to formation of multilamellar vesicles with porelike defects in the bilayers above about 50 oC. The temperature-pressure dependent phase behavior of the binary lipid system DMPC/DHPC has been explored and the transition kinetics between the various phases has been determined.
[1] R. Winter, D. Lopes, S. Grudzielanek, K. Vogtt, J. Non-Equilib. Thermodyn. 32, 41 (2007) [2] R. Winter and R. Köhling, J. Phys.: Condens. Matter 16, 327 (2004) [3] I. Daniel, P. Oger, and R. Winter; Chem. Soc. Rev. 35, 858 (2006) [4] R. Winter and C. Jeworrek, Soft Matter, in press [5] C. Jeworrek, M. Pühse, and R. Winter, Langmuir 24, 11851(2008)
*E-mail : [email protected] Keywords: TRSAXS, pressure jump relaxation technique, lipid phase transition
105
Role of high pressure and various factors on the inactivation of pathogens in biological media
N. Rivalain1, G. Demazeau1, J. Roquain2, A. Largeteau1, J.M. Boiron3, J.P. Maurel3, Z. Ivanovic3.
1CNRS, Université de Bordeaux, ICMCB, site de l’ENSCPB, 87 avenue du Dr. A. Schweitzer, 33608 PESSAC cedex (France)
2Université de Bordeaux - Victor Ségalen- 146 rue Léo-Saignat - 33076 Bordeaux Cedex (France) 3Etablissement Français du Sang Aquitaine Limousin ,
Place Amélie Raba-Léon, 33035 Bordeaux Cedex(France)
The inactivation of pathogens is an important challenge for assuring the safety of various products (foods or/and biological media).
Historically, temperature treatment (in particular pasteurization) was developed for the production of microbiologically safe foods. Over the last thirty years, the use of high hydrostatic pressures (HHP) treatments to inactivate pathogens in foods while retaining the their organoleptic properties has been investigated. One limitation in the development of such processes is often the pressure level required for the inactivation of some resistant pathogens such as Gram-positive bacteria (for example S. aureus).
When the treated product is a biological medium the main challenge is to inactivate the pathogens while retaining the therapeutic properties; in particular the fragile active components.
This presentation will focus on the inactivation of S. aureus in different biological media using pressure and various factors.
*E-mail : [email protected] Keywords : High Hydrostatic Pressure treatments, Safety of Biological media, Preservation of therapeutic properties.
106
Pressure effects on the morphology and migration of mammalian cells
J. Schroeder*1, C.R. Keese2,J. G. Feder3 and I. Giaever1,2. 1Department of Physics, Rensselaer Polytechnic Institute, Troy NY, USA
2Applied Biophysics Inc. Troy NY, USA 3Physics Department, University of Oslo, Oslo, Norway.
Impedance measurements on cells in tissue culture are a relatively new way to monitor how cells change due to chemical or physical alterations in the environment. We have applied a method referred to as Electrical Cell-substrate Impedance Sensing or ECIS to check how cell behavior changes due to high static pressures. In ECIS cells are cultured upon small, 250 micrometer diameter, gold electrodes whose complex impedance is measured with a weak AC signal. When cells attach and spread on these electrodes, their insulating membranes constrain the current, forcing it to flow beneath and between the cells. This results in impedance changes that can be measured and interpreted to quantify cell behavior [1]. The current used is less than a microampere and has no detectable effect upon the cells; hence, the measurement is noninvasive.
A high-pressure vessel has been modified to accommodate electrodes suitable for ECIS measurements allowing studies of cells up to 2 kbar. The cells are first grown to confluence at atmospheric pressure in a CO2 independent medium, and then introduced into the high-pressure chamber for testing. Data from the biosensor will be presented showing how cell morphology change due to various pressure levels.
In addition to morphology changes it is also possible to measure cell migration as a function of pressure. Normally cell migration is measured by scraping (wounding) a small channel in a confluent cell layer. In ECIS, a high voltage pulse is applied for a few second, killing the cells on the small electrode [2] . Then cells from the area surrounding the electrode will crawl in and repopulate the electrode resulting in impedance changes as shown on the figure above.
[1] Giaever, I. and Keese, C.R., "Micromotion of Mammalian Cells Measured Electrically", PNAS USA. 88, 7896 (1991)
[2] Keese, Charles R., Wegener, Joachim, Walker, Sarah R., and Giaever, Ivar. "Electrical Wound-healing assay for cell in vitro". PNAS USA. 101,1554 (2004).
*E-mail : [email protected] Keywords:(pressure effects, mammalian cells, morphology, cell migration )
107
Impact of the composition of the biological medium on pressure inactivation of micro-organisms.
N. Rivalain1, G. Demazeau1, J. Roquain2, A. Largeteau1, J.M. Boiron3, J.P. Maurel3, Z. Ivanovic3.
1CNRS, Université de Bordeaux, ICMCB,site de l’ENSCPB, 87 avenue du Dr. A. Schweitzer, 33608 PESSAC cedex (France)
2Université de Bordeaux - Victor Ségalen- 146 rue Léo-Saignat - 33076 Bordeaux Cedex (France)
3Etablissement Français du Sang Aquitaine Limousin, Place Amélie Raba-Léon, 33035 Bordeaux Cedex(France)
In the research fields involving the inactivation of micro-organisms, it was underlined that the food composition played an important role on the required pressure level.
Using Staphylococcus aureus as a well known pathogen and keeping all the parameters characterizing the High Hydrostatic Pressure Process constant , the impact of the composition of different biological media on the inactivation efficiency was investigated. It was found that the pressure level required for the inactivation of S.aureus is strongly correlated to the composition of such biological media.
*E-mail : [email protected] Keywords : High Hydrostatic Pressure treatments, S. aureus inactivation, Composition of the Biological media
108
Relationship between the volume properties and pressure stability of helical rich proteins
T. Takekiyo* and Y. Yoshimura
Department of Applied Chemistry, National Defense Academy, 1-10-20, Hashirimizu, Yokosuka, Kanagawa, 239-8686, Japan.
Pressure denaturation of proteins in aqueous solution has been investigated using various experimental methods such as NMR and FT-IR spectroscopies
[1]. In recent FT-IR spectroscopic
studies, Meersman et al. [2]
showed that the α-helix structures of myoglobin broke above 400 MPa, and completely denaturated at 700 MPa. Desai et al.
[3] reported the α-helix structures
of trp-repressor were maintained at 800 MPa. Subsequently, we have reported that the α-helix structures of oligopeptide
[4,5], polypeptide
[6], and de novo designed helical protein
[7] was
stabilized under high pressure. Even for the similar α-helical proteins and peptides, the pressure stabilities of the secondary structure are different from each other. In this study, we have calculated the volume properties of various helical peptides and proteins to investigate the relationship between the pressure stability and volume properties of helical proteins using simple volume calculation method. We have calculated the van der Waals volume (Vw), molecular volume (VM), and intra-cavity volume (Vc) using various probe radiuses. Our result showed that the intra-cavity volume per amino acid residue (Vc/a.a) of peptides and proteins non-linearly increases with increasing amino acid residues. We suggest that the non-linear increase of Vc/a.a value of peptides and proteins may relate to the pressure stability of helical protein.
[1] W. Dzwolak, M. Kato, Y. Taniguchi, Biochim. Biophys. Acta 1595, 131 (2002). [2] F. Meersman, L. Smeller, K. Heremans, Biophys. J. 82, 2635 (2002). [3] G. Desai, G. Panick, M. Zein, R. Winter, C. A. Royer, J. Mol. Biol. 288, 461 (1999). [4] T. Takekiyo, A. Shimizu, M. Kato, Y. Taniguchi, Biochim. Biophys. Acta 1750, 1 (2005). [5] T. Takekiyo, T. Imai, M. Kato, Y. Taniguchi, Biochim. Biophys. Acta 1764, 355 (2006). [6] T. Takekiyo, Y. Yoshimura, A. Okuno, A. Shimizu, M. Kato, Y. Taniguchi, J. of Phys.:Conf. Ser.
121, 042003 (2008). [7] T. Takekiyo, N. Takeda, Y. Isogai, M. Kato, Y. Taniguchi, Biopolymers 85, 185 (2006).
*E-mail : [email protected] Keywords; Helical protein, Pressure stability, Volume calculation
109
Investigation of L-histidine.HCl.H2O crystals by Raman spectroscopy under high pressure conditions
G.P. De Sousa*1, P.T.C. Freire1, F.E.A. Melo1, J. Mendes Filho1, J.A. Lima Jr.2 1Universidade Federal do Ceará, Fortaleza, Brazil
2Universidade Estadual do Ceará, Limoeiro do Norte-CE, Brazil
Since the publication of the first work on high pressure properties of an amino acid crystal[1] a great number of studies on this subject has been published[2]. They deal mainly with vibrational and structural aspects of crystals. From these studies was possible to understand that most of investigated amino acid crystals present some kind of anomalies under high pressure conditions and, in some cases, solid-solid phase transitions. For example, just to cite the simplest chiral amino acid, it was discovered that L-alanine undergoes a phase transition from a orthorhombic to a tetragonal structure at ~ 2.2 GPa[3]. In the present work we will show results related to L-histidine.HCl.H2O crystal by Raman spectroscopy. We have investigated the spectral region 30 – 3500 cm
-1 with spectra being recorded up to 7.5 GPa.
From the spectra we were able to note a series of modifications between 2.7 and 3.0 GPa. The main changes are: (i) disappearing of two bands around 3375 cm-1 and the appearing of a new band above 3400 cm
-1; (ii) frequency jump of a band at ~ 3150 cm
-1; (iii) the splitting of a
band at ~ 1620 cm-1
, which is associated to a stretching vibration of C = O; (iv) jump of frequency of a band at 700 cm
-1, which is associated to a deformation vibration of CO2 unit;
(v) disappearing of bands at ~ 520 cm-1
; (vi) splitting of a band at 180 cm-1
. All this picture points to a phase transition undergone by L-histidine.HCl.H2O at pressure values between 2.7 and 3.0 GPa. We remember that L-histidine.HCl.H2O crystallizes in a P212121 orthorhombic structure and the molecules are held together by a complex network of hydrogen bonds. The pressure, as occur with other amino acid crystals, changes the conformation of the molecules via deformation of hydrogen bond, eventually changing the symmetry of the unit cell. Possibly the phase transition undergone by the material investigated in our work is due the change of hydrogen bond between the oxygen of CO2 units and hydrogen of NH3 units, as occurs with other amino acid crystals; studies of the structural properties of the crystal under high pressure through X-ray diffraction are being performed.
[1] A. J. D. Moreno, P. T. C. Freire, F. E. A. Melo, M. A. A. Silva, I. Guedes, J. M. Filho, Sol. State Commun. 1997, 103, 655.
[2] E. V. Boldyreva, E. V. Kolesnik, T. N. Drebushchak, H. Sowa, H. Ahsbahs, Y. V. Seryotkin, Z. Kristallogr. 2006, 221, 150 (and references therein).
[3] A. M. R. Teixeira, P. T. C. Freire, A. J. D. Moreno, J. M. Sasaki, A. P. Ayala, J. M. Filho, F. E. A. Melo, Sol. State Commun. 2000, 116, 405.
*E-mail : [email protected] Keywords: amino acid, Raman spectroscopy, phase transition
110
High pressure vibrational properties of L-isoleucine crystals
P.T.C. Freire*1, A.S. Sabino1, G.P. De Sousa1, C. Luz-Lima1, F.E.A. Melo1, J. Mendes Filho1
1Universidade Federal do Ceará, Fortaleza,Brazil
Amino acids are the building blocks of all proteins. The simplest amino acids are the aliphatic ones: glycine, L-alanine, L-valine, L-leucine and L-isoleucine. Under high pressure conditions glycine presents a complex behavior, depending on the original polymorph crystal (α, β or γ) put into the diamond anvil cell [1]. L-alanine, L-valine and L-leucine were also investigated under high pressure conditions and for all of them it was possible to observe anomalies in the Raman spectra of the crystals. Such anomalies were associated both to conformational change of the molecules in the unit cell or to a solid-solid phase transition undergone by the crystal [2-4]. In this work we present the Raman spectra of L-isoleucine crystal for pressures up to 7.5 GPa. In the high wavenumber region of the spectrum 2800 – 3100 cm
-1, where one
can observe bands associated to stretching vibrations of CH and CH3, it was possible to note changes in the bands profiles which can be related to molecular conformational modification in the unit cell. The spectral region between 600 and 1150 cm
-1,
a region where bands associated to stretching of C-C and bending of CO2 appears, among others, it was observed several modifications of the band profiles at ~ 2.2 and 5 GPa. In particular, it is very clear the disappearing of a band associated to stretching of C-N, as well as, the increasing of intensity of a band associated to C-C stretching. Additionally, modification in the low wavenumber region at the same pressures confirms the changes observed in the internal mode region of the spectra, indicating that L-isoleucine crystal presents pressure induced anomalies at 2.2 and 5 GPa (Figure 1).
[1] E. V. Boldyreva, Crystalline amino acids. In Models, Mysteries, and Magic of Molecules; J.C.A.Boeyens, J.F. Ogilvie, Eds. Springer-Verlag: New York, 2007; pp. 169 – 194.
[2] A. M. R. Teixeira, P. T. C. Freire, A. J. D. Moreno, J. M. Sasaki, A. P. Ayala, J. M. Filho, F. E. A. Melo, Sol. State Commun. 116, 405 (2000).
[3] J. H. Silva, V. Lemos, P. T. C. Freire, F. E. A. Melo, J. M. Filho, J. A. Lima Jr., P. S. Pizani, phys. stat. sol. (b) 246, 553 (2009).
[4] P. F. Façanha Filho, P. T. C. Freire, F. E. A. Melo, V. Lemos, J. M. Filho, P. S. Pizani, D. Z. Rossatto, J. Raman Spectrosc. 40, 46 (2009).
*E-mail : [email protected] Keywords: Raman spectroscopy, amino acid, phase transition
Figure 1: wavenumber vs pressure of L-isoleucine crystal
111
High pressure vibrational properties of L-proline
B.T.O. Abagaro1, V. Lemos*1, P.T.C. Freire1, J.A. Lima Jr2, F.E.A. Melo1, J. Mendes Filho1
1Universidade Federal do Ceará, Fortaleza,Brazil 2Universidade Estadual do Ceará, Limoeiro do Norte, Brazil
Proline is known to be a cryoprotectant for plants, bacteria, invertebrates, protozoa and algae, and, for animals, it participates in the formation of several proteins. In this contribution we report results on the effects of hydrostatic pressure applied on the crystal of the amino acid L-proline, using Raman spectroscopy as probe of changes of its vibrational properties. In the solid state L-proline occurs in the zwitterionic form; differently from the other protein-
forming amino acid the -group is secondary. At atmospheric pressure the crystal L-proline belongs to a space group with point symmetry C1. The 45 vibrational modes give rise to a richly structured Raman spectrum with Raman bands spreading through the complete spectral region comprised between 50 cm
-1 and 3000 cm
-1. Under pressure the Raman
spectrum changes to a much less structured profile with broadening of peaks and a generalized decreasing of intensities. The changes are strong enough to make the peaks disappear in several regions while in some of them just weak, broad bands prevail for pressures as high as 9 GPa. In particular, it was observed a great modification of Raman profile in the low wavenumber region, where the lattice modes of the crystal are expected to occur. Important changes in the profile were also observed in the wavenumber region where C-H stretching vibrations generally occur. Such modifications were interpreted in terms of conformational change of proline molecules in the unit cell. On releasing the pressure from this value, a fully structured Raman spectrum is recovered.
*E-mail : [email protected] Keywords: Raman spectroscopy, amino acid, phase transition
112
Role of the metastable states in the sequential character of the aggregation of the pressure treated lysozyme
K. Szigeti, D. Lakatos, L. Smeller*
Semmelweis University Dept. Biophysics and Radiation Biology Budapest, Hungary
Importance of the pressure induced metastable protein conformations in the misfolding and aggregation has been recognized recently. These partially disordered metastable intermediates can be gates for the misfolding pathway that leads sometimes to pathological structures, like fibrous aggregates. We have shown that high pressure is a very useful tool in the study of metastable states, because of the pressure sensitivity of some of the aggregates [1]. FTIR spectroscopy allows us to follow simultaneously the secondary structure, the packing (tertiary structure) and the aggregation of the protein using the amide I, amide II and the 1616 cm
-1 bands respectively.
We performed a systematic study of the temperature-pressure phase diagram of lysozyme and found a two-step unfolding profile both in the pressure and temperature directions. Hydrogen/deuterium exchange results show evidence for the molten globule formation at 57°C @130 MPa and 580 MPa @30°C, which are considerable lower values than those of the complete unfolding (e.g. 75°C@130MPa).
Kinetics of the refolding of the protein after a pressure unfolding cycle shows, that the complete refolding is a rather slow process, with a time constant in the order of magnitude of few hours. The partially refolded structures present in this time range have different aggregation propensity, depending on the temperature. The kinetics of the aggregate formation has a multiexponential character.
Analyzing the time dependence of the amide I band shape we found that the strengthening of the intermolecular hydrogen bond network was accompanied by decrease of the folded secondary structure content.
A theoretical model describing the sequential role of the aggregation has been developed and tested using the kinetic results obtained on the pressure treated lysozyme.
[1] L Smeller, Acta - Protein Structure et Molecular Enzymology 1595, 11 (2002). [2] L. Smeller, F. Meersman, K. Heremans, Biochim Biophys. Acta Proteins Proteomics 1764,
497 (2006)
* E-mail : [email protected] Keywords: protein, aggregation, infrared spectroscopy, metastable states
113
Thermodynamics of the pressure unfolding of phosphoglycerate kinase
S. Osváth, L.M. Quynh, and L. Smeller*
Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
Due to the relationship between compressibility and volume fluctuations, high pressure studies provide vital insight into protein dynamics and function. Most high pressure experiments were performed on small and fast folding proteins, or model peptides. Here we show that a detailed kinetic study is necessary to extract reliable information from the high pressure induced structural conversion of large, slowly folding proteins. The pressure jump unfolding kinetics of yeast phosphoglycerate kinase (PGK) was recorded at pressures between 50 and 150 MPa. The time dependence of the conformational state of the protein was followed by tryptophan fluorescence measurements from 30 s to 2 hours. The observed changes were described by a three-state model, and the volume change, the activation volume as well as the midpoint pressure of the transitions between the folded, intermediate and unfolded states were determined. An interesting feature of the pressure unfolding of PGK was that the unfolding process speeds up with increasing pressure, which is the consequence of negative activation volumes.
* E-mail : [email protected] Key words: protein folding; phosphoglycerate kinase; high pressure; unfolding
114
Paper has been withdrawn by the authors
R. Hazael1, D. Vanlint2, E. Bailey1, A. Aertsen2, C. Michiels2, F. Meersman2, P. F McMillan1
1 University College London, Christopher Ingold Laboratories, 20 Gordon St, London WC1H 0AJ
2 Katholieke Universiteit Leuven, Centre for Food and Microbial Technology, Centr. Levensmidd.- & Microb. Technol., Kasteelpark Arenberg 22, Heverlee, Belgium
115
Advances in Laboratory Techniques
Lectures Determination of thermal conductivity of materials in laser-heated DAC ___________ 117
Ruby microcrystal as a stress sensor _________________________________________ 118
New measurements on helium at High pressure. _______________________________ 119
Laser Ultrasonics in Diamond Anvil Cell (LU-DAC) technique for elastic properties
measurements at high pressures _____________________________________ 120
Posters LT 01 : Practical, affordable and precise: Diamond-Cells and Laser- Heating
System __________________________________________________________ 121
LT 02 : Experimental and Theoretical Analysis of Moissanite Anvil Cells for
Uniaxial Stress Experiments on Carbon-based Materials _________________ 122
LT 03 : Influence of structure and orientation of graphite on its polymorphic
transformation under shock compression _____________________________ 123
LT 04 : Influence of initial temperature of graphite on parameters and kinetic of
transformation into diamond at shock-wave loading ____________________ 124
LT 05 : High pressure luminescence study in Sm3+
:K-Ba-Al fluorophosphate
glasses __________________________________________________________ 125
LT 06 : A new DTA set-up for measuring high pressure phase transitions ___________ 126
LT 07 : High pressure Raman spectra of Na2MoO4.2H2O crystals __________________ 127
LT 08 : Turnbuckle diamond anvil cell for magnetic measurements in a SQUID
magnetometer ___________________________________________________ 128
LT 09 : New approaches for probing of phase transitions under pressure ___________ 129
LT 10 : Composite fabric pressure cell for a SQUID magnetometer ________________ 130
LT 11 : Toroidal diamond anvils ____________________________________________ 131
LT 12 : Hydrostatic limits of 11 pressure transmitting media _____________________ 132
LT 13 : High-Pressure Hydrogen Storage for On-Board Applications and for
Coupling Renewable Energies to the Electric Grid _______________________ 133
LT 14 : Implantation of Pressure-Temperature Sensors and Conductive
Electrodes in Diamond Anvils (i-anvils): First Results _____________________ 134
LT 15 : A new diamond anvil cell for in situ spectroscopy study of geological
fluids ___________________________________________________________ 135
LT 16 : Electrical characterization of a quartz crystal in high pressure CO2 by
impedance analysis _______________________________________________ 136
LT 17 : Raman spectroscopy study of nitromethane in a shear diamond anvil cell ____ 137
116
117
Determination of thermal conductivity of materials in laser-heated DAC
Z. Konopkova1, P. Lazor*1, A. F. Goncharov2, V.V. Struzhkin2 1Department of Earth Sciences, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden
2Geophysical Laboratory, Carnegie Institution, 5251 Broad Branch Rd. NW, Washington DC, 20015, USA
Thermal conductivity of materials in planetary interiors belongs to key parameters controlling thermal evolution and dynamics of planets. Yet it is insufficiently constrained, in particular under the deep mantle and core conditions. For example, thermal conductivity of iron alloy in the Earth’s core has been recently revised by a factor of two [1]. Laser-heated diamond anvil cell technique offers, in principle, possibility for the experimental determination of thermal conductivity at extreme conditions, provided that the boundary conditions of sample assemblage are precisely characterized and controlled. Indeed, feasibility of such studies has been demonstrated in a number of heat-transfer simulations in DAC utilizing finite element method [e.g. 2], as well as in a recent pioneering study on the transient heat propagation facilitated by a pulsed laser heating [3].
We will present results of steady-state heat transfer experiments combined with numerical simulations (COMSOL) on the high pressure thermal conductivity of iron in LHDAC, carried out in the HP laboratory as well as at the APS. We assess the effects of uncertainties and trade-offs between various parameters on the determination of conductivity. For the explored case of a thin foil of iron embedded in MgO, the key parameters, which have to be measured with a high precision and accuracy include radial temperature gradients on both sides of the foil, power distribution profile in the laser beam, and exact 3D geometry of the sample assemblage, including the pressure medium and adjacent gasket. Determination of the amount of absorbed laser power, especially at high temperatures, represents a challenge. State-of-the-art measurements will have to address also the effects of spatially varying thermal stress during a laser heating, and of the extrinsic anisotropy in thermal conductivity induced by preferred-orientation effects and a large uniaxial stress component. Diffusion, chemical reaction, and oxidation at the sample - pressure medium interface may result in the creation of a thin but potentially significant thermal barrier affecting the heat flow. We will discuss these issues and outline possibilities for a solution.
[1] F. D. Stacey, D. E. Loper, Phys. Earth Planet. Int. 2007, , 13. [2] B. Kiefer, T. S. Duffy, J. Appl. Phys. 2005, , 114902. [3] P. Beck, A. F. Goncharov, V. V. Struzhkin, B. Militzer, H. K. Mao, R. J. Hemley, Appl. Phys.
Lett. 2007, , 181914.
E-mail : [email protected]
Thermal conductivity, pressure, laser-heated diamond anvil cell, iron
118
Ruby microcrystal as a stress sensor
K. Takemura*
National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044, Japan
Ruby is a standard pressure gauge in the high-pressure experiments with a diamond-anvil cell (DAC)[1]. Crashed ruby grains or powders have been used for this purpose. Small ruby spheres of 1-50 micron size[2] are also used in many laboratories. Ruby spheres have sharp and strong luminescence, if properly prepared. One can easily find a sphere with suitable size for desired experiments. These characteristics have made the ruby sphere popular in recent years. However, it has one disadvantage: unknown crystallographic orientation. The R1-R2 separation of the ruby luminescence lines is a good measure of hydrostaticity, and the effect of nonhydrostatic stress has been thoroughly studied[3]. If uniaxial stress is applied along the a-crystallographic direction, the R1-R2 separation increases, while if the stress is applied along the c-direction, the separation decreases. Hence the exact stress state in a DAC is difficult to evaluate from the R1-R2 separation of ruby spheres (and grains or powders) with unknown orientation. In order to overcome the problem, we have prepared ruby microcrystal with welldefined crystallographic orientation. So far, we have made small ruby cubes of ~10 x 10 x 6 micron and micro-disks of 10 micron diameter and 3 micron thickness. The details of sample preparation and its performance in the DAC experiments will be presented.
[1] K. Syassen, High Press. Res. 28, 75 (2008). [2] J. C. Chervin, B. Canny, M. Mancinelli, High Press. Res. 21, 305 (2001). [3] M. Chai, J. M. Brown, Geophys. Res. Lett. 23, 3539 (1996).
*E-mail : [email protected]
Keywords: ruby, diamond-anvil cell, uniaxial stress
119
New measurements on helium at high pressure.
P. Loubeyre*1, S. Brygoo1, F. Occelli1, P. Celliers2, J. Eggert2, G. Collins2, R. Jeanloz3 1CEA, Bruyères-le-Châtel, 91297 Arpajon. France
2LLNL, Livermore, California, 94551. USA 3University of California, Berkeley, California. USA.
Helium is the second most abundant element in the universe and its phase diagram continues to be a rich playground for condensed matter physics. Specifically under pressure, the determination of its equation of state and the domain in phase space where condensed helium makes the transition to the electrically conducting state are of particular interest.
However up to now the measurements under pressure have been quite limited and done more than 15 years ago. The equation of state was measured in the solid, under static compression by x-ray diffraction up to 58 GPa, and in the fluid, under dynamical compression up to 56 GPa. We will present recent experiments that significantly extend these previous determinations. First, single crystal x-ray diffraction at the ESRF has been measured up to 200 GPa at 300 K and at 6 K. No phase transition is observed. Second, Hugoniot data have been obtained in the 100 GPa pressure range by laser shock compression of samples statically pre-compressed in diamond anvil cells. Third, reflectivity measurements in the dense fluid show the insulator to conductor transition in dense helium. A density dependence of the electronic gap is disclosed.
These experimental data will be compared to various recent calculations and that constitutes a stringent test of the various physical models describing the ionization of helium at conditions found in astrophysical objects. An updated phase diagram of helium will finally be presented.
[1] J. Eggert, S. Brygoo, P.Loubeyre et al Phys. Rev. Lett. 100, 124503 (2008).
*E-mail : [email protected]. Keywords (Helium, Insulator/metal, Equation of state).
120
Laser ultrasonics in diamond anvil cell (lu-dac) technique for elastic properties measurements at high pressures
N. Chigarev1, P. Zinin2, L.C. Ming2, G. Amulele2, A. Bulou3, V. Gusev3
1LAUM, CNRS, Université du Maine, Avenue Olivier Messiaen, 72085 Le Mans, France 2HIGP, University of Hawaii, Honolulu, Hawaii, USA
3LPEC, CNRS, Université du Maine, Avenue, Olivier Messiaen, 72085 Le Mans, France
Acousto-optical method of Brullouin scattering is traditionally applied for characterization of the material elasticity
1. Only recently the opto-acousto-optical methods, which in additional
to optical detection of acoustic waves exploit optical generation of acoustic waves, have been proposed for the same purpose
2-4. The method of impulsive stimulated light scattering (ISLS)
2
includes generation of quasi-monochromatic interface acoustic waves by laser-induced grating. The method of picosecond laser ultrasonics (PLU)
3 is based on the generation and
detection of the bulk plane longitudinal acoustic pulses by femtosecond lasers. In this communication we present for the application in diamond anvil cell (DAC) the technique of laser ultrasonics (LU) in point-source-point-receiver configuration
4 (LU-DAC technique) which
is based on optical generation and detection of diffracting longitudinal and shear acoustic pulses.
The beams of pulsed subnanosecond 1064 nm Nd:YAG and continuous 532 nm lasers are focused on the surface of the sample by the same objective through diamond window of the cell Fig. 1.
Figure 1. Scheme of the LU-DAC technique. The rays ABD and ACD correspond to longitudinal and longitudinal mode-converted into shear acoustic pulses propagation.
Both longitudinal and shear strain pulses are launched into the system by the absorption of pulsed laser radiation in point A and detected at point D due to modulation of CW laser reflectivity by acoustic arrivals. The arriving times τ(d) of the echoes corresponding to several different distances between laser beams d are measured. The sound velocities and film thickness h are determined from the fit of the experimental points. We present the measurements of the elastic properties of several transparent and opaque materials by this technique. In addition to bulk acoustic modes the LU-DAC technique provides, similar to ISLS technique
2, an opportunity of monitoring interface and skimming
bulk waves propagating along the diamond/material surface. In comparison with PLU technique
3 LU-DAC provides opportunity to directly investigate shear acoustic velocity of
materials by monitoring shear or mode-converted, or head waves and does not require additional information on variation of sample thickness with pressure.
[1] A. Polian, M. Grimsditch, Phys. Rev. B 27, 6409 (1983). [2] J. C. Crowhurst et al., J. Phys.: Condens. Matter 16, S1137 (2004). [3] F. Decremps, L. Belliard, B. Perrin, M. Gauthier, Phys. Rev. Lett. 100, 035502 (2008). [4] N. Chigarev, et al., Appl. Phys. Lett. 93, 181905 (2008).
121
Practical, affordable and precise: diamond-cells and laser- heating system
R. Boehler
Max-Planck-Institut für Chemie, Postfach 3060, D-55020 Mainz, Germany
A compact, double-sided laser-heating system for diamond-cell synchrotron applications is described. The pre-aligned optical table contains laser, spectrometer, all optics and mechanical drives for visual observation and rapid alignment and for measuring temperatures and pressures. This unit can be set up at most synchrotron beamlines within about one hour. The cost of all components is below 50 k€. The diamond cells are designed for symmetrical optical access and large aperture, which allow off-axis laser-heating and large diffraction angles. We carried out measurements on iron, molybdenum, tungsten and xenon up to over one megabar and up to over 4000 K at the X-ray diffraction beamline ID 27 at the European Synchrotron Facility (ESRF) and obtained first spectra of molten iron at the X-ray absorption beamline ID 24.
* E-mail : [email protected]
122
Experimental and theoretical analysis of moissanite anvil cells for uniaxial stress experiments on carbon-based materials
E. del Corro*1, M. Taravillo1, P. Pertierra2, M.A. Salvadó2, J.M. Recio2, V. García-Baonza 1
1MALTA-Consolider Team, Dpto. Química Física I, Universidad Complutense de Madrid, Spain
2MALTA-Consolider Team, Dpto. Química Física y Analítica, Universidad de Oviedo, Spain
The interest in nano-science has stimulated an increasing research on graphite and other carbon related materials. The behaviour of these materials with increasing pressure has been extensively studied in the hydrostatic regime. Our current interest concerns the effect of uniaxial stress on such carbon-based materials. For this purpose we use Raman spectroscopy. Carbon based materials exhibit Raman features in the spectral range where the most intense signal of diamond appears. Moissanite is a better suited anvil
1 to conduct our experiments
2 as
its Raman features (second order spectrum), in the spectral window of interest, are less intense than that of diamond. Moreover, this overlapping represents an advantage since the local effective stress can be estimated from the Raman spectra of moissanite without using a pressure marker, thus avoiding bridging between the anvils since the sample must be placed directly onto the anvil surface. A typical stress profile across the moissanite anvil cell (MAC) of one of our experiments is shown in the following figure.
Stress profile inside the MAC measured along the black line indicated in the photograph.
In order to systematize these experiments, it is essential to know the mechanical properties of moissanite under both uniaxial and hydrostatic pressure conditions. In this work we present a combined experimental and theoretical study of moissanite in both regimes. We measured the Raman spectrum of moissanite under uniaxial stress. A blueshift of the spectra is observed and this variation is compared with DFT-LDA calculations. These calculations have also been performed for hydrostatic conditions and compared with existing experimental works.
3,4
[1] J. Xu, H. K. Mao, R. J. Hemley, E. Hines, J. Phys.: Condens. Matter 14, 11543 (2002). [2] E. del Corro, J. González, M. Taravillo, E. Flahaut, V. G. Baonza, Nano Lett. 8, 2215 (2008). [3] J. Liu, Y. K. Vohra, Phys. Rev. Lett. 72, 4105 (1994). [4] Z. Liu, J. Xu, H. P.Scott, Q. Williams, H. K. Mao, R. J. Hemley, Rev. Sci. Instrum. 75, 5026
(2004).
*E-mail : [email protected]
Keywords: moissanite, uniaxial pressure, Raman spectroscopy, DFT calculations
123
Influence of structure and orientation of graphite on its polymorphic transformation under shock compression
G.G. Bezruchko1*, G.I. Kanel2, S.V. Razorenov1, A.S. Savinykh1, V.V. Milyavskiy2, K.V. Khishchenko2
1 Institute of Problems of Chemical Physics RAS, Chernogolovka, Russia 2Joint Institute for High Temperatures RAS, Moscow, Russia
Measurements of the transition pressure and rate under shock compression of different graphites at different sample orientations have been carried out with the goal to verify possible mechanisms of the graphite-diamond transformation. The materials tested were highly ordered synthetic graphite plates and samples prepared by pressing of powders of highly ordered pure graphite and several kinds of natural graphite. In experiments the VISAR wave profiles were measured using the LiF windows in the transformation pressure region. It has been found the shock direction significantly affects the detected pressure of the transformation and its rate. Results of the measurements show that means shifts in basal planes complicate high-rate graphite–diamond transformation. The effect is more pronounced in more ordered graphite. It was found also the transformation pressure increases and the transformation rate decreases as the degree of three-dimensional ordering of graphite decreases. Content of rhombohedral phase (up to 30%) does not much influence on the transformation parameters.
*E-mail : [email protected]
Keywords: Graphite, phase transformation, shock wave, interferometer VISAR
124
Influence of initial temperature of graphite on parameters and kinetic of transformation into diamond at shock-wave loading
A.S. Savinykh*1, G.I. Kanel2, S.V. Razorenov1, G.S. Bezruchko1, K.V. Khishchenko2 1Institute of Problems of Chemical Physics of RAS, Chernogolovka, Russia
2 Joint Institute for High Temperatures of RAS, Moscow, Russia
Transformation into diamond-like phase in shock-compressed natural graphite of two types was studied at normal and elevated temperatures. In the experiments, the velocity histories of the interface between the sample and LiF window were recorded. The shock-wave loadings were created by impact of aluminum flyer plates accelerated up to velocity ~3130 m/s. The interpretation of the data obtained was carried out using the wide-range equations of state of graphite, LiF and aluminium at initial temperatures 20 and 470° С. Calibrating experiments for determination of correction of the constant of interferometer VISAR at high temperature were carried out. Thus, in this work, the technique of shock-wave experiments with LiF "window" at elevated temperatures was developed and it was shown, with increase initial temperature of graphite, the pressure of phase transition graphite – diamond decreases, the speed of the second shock wave and the speed of transformation graphite – diamond increase.
*E-mail : [email protected]
Shock wave, phase transition, graphite, profile of particle velocity.
125
High pressure luminescence study in Sm3+:K-Ba-Al fluorophosphate glasses
C.K. Jayasankar1*, L .Jyothi1, Ch. Basavapoornima1, Th. Tröster2, W. Sievers3 and G. Wortmann3
1 Department of Physics, Sri Venkateswara University, Tirupati-517 502, India 2Fakultät für Maschinenbau, Universität Paderborn, D-33098 Paderborn, Germany
3Department Physik, Universität Paderborn, D-33095 Paderborn, Germany
Pressure dependent fluorescence spectra and decay curves for the 4G5/2 level of Sm
3+ ions in
(56-x/2)P2O5 + 14K2O + (15-x/2)BaO + 9Al2O3 + 6KF + x Sm2O3 (where x = 0.1 and 1.0 mol %) glasses, referred as PKFBASm01 and PKFBASm10, have been studied up to 40.5 GPa at room temperature. With an increase in pressure continuous red shifts of the
4G5/2→
6HJ (J = 9/2, 7/2
and 5/2) multiplet transitions as well as progressive increase in the magnitude of the splittings for these transitions are observed. The magnitude of red shift for
4G5/2→
6H9/2,7/2, 5/2 transitions
are found to be -5.3, -4.7 and -5.2 cm-1
/GPa for PKFBASm01 glass and -4.7, -4.5 and -5.2 cm
-1/GPa for PKFBASm10 glass, respectively (Fig.1). The decay curves for the
4G5/2
level of Sm3+
ions in PKFBASm01 are found to exhibit single exponential behavior at ambient pressure and become non-exponential at high pressures accompanied by shortening of lifetimes (Fig. 2(a)) where as these curves are found to exhibit non-exponential nature in KFBASm10 glass for the entire pressure range studied (Fig. 2(b)). A generalized Yokoto-Tanimoto model has been used to explain the pressure-induced non-exponential nature of the decay curves. The decrease in lifetime of the
4G5/2 level with pressure can be attributed to
the increase in the crystal-field strength felt by the Sm3+
ions due to volume reduction accompanied by a simultaneous increase in the electronic transition probabilities. The results are comparable to those of similar studies on Sm3+-doped lithium borate[1] and niobium phosphate[2] glasses.
Fig.1.Emission spectra of (a) PKFBASm01 and (b) PKFBASm10 glasses at different pressures.
Fig.2.Decay profiles for the 4G5/2 level of Sm
3+
in (a) PKFBASm01 and (b)PKFBASm10 glasses at different pressures.
Acknowledgements: This work has been carried out under a Major Research Project supported by DAE-BRNS, Govt. of India (No. 2007/34/25-BRNS/2415, dt. 18-01-2008).
[1] C.K.Jayasankar, V.Venkatramu, P.Babu, Th. Tröster, W. Sievers , G. Wortmann and W.B.Holzapfel, J.App. Phys. 97, 093523 (2005).
[2] R.Praveena, V.Venkatramu, P.Babu, Th. Tröster, W. Sievers, G. Wortmann J.Phys.: Condens Matter, 21, 035108 (2009).
*E-mail : [email protected]
Keywords: Sm3+
:glasses, Luminescence at extreme conditions, Decay curves, Energy transfer
126
A new DTA set-up for measuring high pressure phase transitions
C. Goujon*, M. Legendre, P. Plaindoux, A. Prat and R. Bruyère
Institut Néel / CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9, France.
Differential Thermal Analysis (DTA) is a widely used experimental technique to study phase transitions during controlled heating or cooling. The measurement of a temperature difference between a sample and a reference leads to the detection of first order transitions, such as melting, crystallization, decomposition, and some second order transformations such as vitreous transitions or magnetic ordering.
However, investigations to adapt this technique to high pressure cells are still restricted [1-5]. The small volume available to insert thermocouples and the large deformations undergone by the solid transmitting medium make in-situ temperature measurements very difficult to perform and require a special design of the sample holder.
In this study, we propose a new assembly to carry out DTA in Conac anvil-type apparatus. As for a standard DTA set-up, two symmetrical crucibles, respectively for the sample and the reference, are inserted in the high pressure cell. The temperatures of both crucibles and the differential signal DT between the sample and the reference are measured by two Pt-Pt 10% Rh thermocouples (S type) of diameter 0.25 mm placed just under the crucibles. The performances of the system allow the thermal analysis of powder samples up to 6 GPa and 1500°C.
The presentation will describe the features of this new assembly and, as preliminary results, the melting points under high pressure of different pure elements or compounds.
[1] G.C. Kennedy, R.C. Newton, in Solids Under Pressure, edited by W. Paul and D. Warschauer, McGraw-Hill Book Company, Inc., New York, 1962.
[2] A. Jayaraman, R.C. Newton, J.M. McDonough, Phys. Rev. 159, 527 (1967). [3] V.A. Sidorov, Appl. Phys. Lett. 72, 2174 (1998). [4] C. Susse, R. Epaix, B. Vodar, CRAS 258, 4513 (1964). [5] T.G. Ramesh, V. Shubha, J. Mater. Sci. 41, 1617 (2006).
*E-mail : [email protected]
Keywords : Differential thermal analysis, Conac anvils, phase transitions
127
High pressure Raman spectra of Na2MoO4.2H2O crystals
C. Luz-Lima*, P.T.C. Freire, G.D. Saraiva, W. Paraguassu, A.G. Souza Filho, J. Mendes Filho
1Universidade Federal do Ceará, Fortaleza,Brazil 2Universidade Estadual do Ceará, Quixadá, Brazil
3Universidade Federal do Maranhão, São Luis, Brazil
Raman spectroscopy measurements of polycrystalline Na2MoO4.2H2O under high pressure conditions (0 – 10 GPa) were performed. Na2MoO4.2H2O belongs to a set of inorganic compounds with general formula Y2XO4.nH2O, where Y= (Na, Ca), X= (Mo, S, W, Mn) and n = (0, 1, 2, 3, 4,…) has been the subject of considerable interest in recent years due their very interesting physico-chemical properties
[1]. The present study allowed us to monitor the
stretching and bending vibrations of MoO4 ions as well as the translational modes in the 50 – 1000 cm
-1 wavenumber spectral region as a function of pressure. Upon increasing pressure
the Raman spectra remain qualitatively similar up to 3.0 GPa. At this pressure it is observed some changes in the Raman spectrum. Changes are also observed at ~ 3.6 GPa, such as the collapse of external modes which is an indicative of a structural phase transition from a low to a higher symmetry phase. The first transition was classified as conformational, where the crystal remains in the orthorhombic structure, but changes the space group. The second phase transition, from the phase β to the phase δ has characteristics of a structural phase transition where the material changes from an orthorhombic symmetry possibly to a tetragonal one. In this second phase transition some interesting aspects are observed and
discussed, such as the softening of the stretching modes which exhibit a negative dɷ/dP slope, similar to the that observed for NaAl(MoO4)2
[2]. When pressure is released the original phase
is obtained when we use the nujol as hydrostatic pressure transmitting medium. However, when we use the ethanol:methanol 1:4 mixture as compression medium, the alcohol affects the sample promoting a partial dehydration. As a consequence, the original phase is not obtained after decompression due the interaction between pressure transmitting medium and the sample.
[1] V. P. Mahadevan, T. Pradeep, M. J. Bushiri, R. S. Jayasree, V. U. Nayar, Spect. Acta A 35, 867 (1997).
[2] W. Paraguassu, A.G. Souza Filho, M. Maczka, P.T.C. Freire, F.E.A. Melo, J. Mendes Filho, J. Hanuza, J. Phys. Cond. Matter 16, 5151 (2004).
*E-mail :[email protected]
Keywords: Raman spectroscopy, molibdate, phase transition
128
Turnbuckle diamond anvil cell for magnetic measurements in a SQUID magnetometer
G. Giriat, W. Wang, K. V. Kamenev*
School of Engineering & Centre for Science at Extreme Conditions, University of Edinburgh, Edinburgh, UK
The Magnetic Property Measurement System (MPMS) from Quantum Design is probably the most advanced, user friendly and, therefore, the most popular Superconductive Quantum Interference Device (SQUID) magnetometer in the world. There has been two opposed anvil designs of high pressure cells designed to work with this magnetometer and generating pressure in excess of 2 GPa
[1-2]. One of the challenges in these designs is accommodating and
using the mechanism for aligning the diamonds. Here we present a simple design (Fig. 1) based on the turnbuckle principle
[3]. The body of the cell and the gasket are made of non-
magnetic BERYLCO-25 alloy. The pressure cell is fully symmetric with respect to the sample and weighs only 1.5 g. This results in a low magnetic background which made it possible to use this cell for studies of weakly magnetic materials.
Fig. 1 Turnbuckle diamond anvil cell for magnetic measurements (dimensions are in mm).
[1] M. Mito et al, Jpn. J. Appl. Phys. 40, Part 1, No. 11, 6641 (2001). [2] P. L. Alireza, G. G. Lonzarich, Rev. Sci. Instrum. 80, 023906 (2009). [3] M. Kano et al, J. Phys. Soc. Jpn. 76, Suppl. A, 56 (2007).
*E-mail : [email protected]
Turnbuckle design; Diamond anvil cell; SQUID magnetometer
129
New approaches for probing of phase transitions under pressure
V.V. Shchennikov* and S.V. Ovsyannikov
High Pressure Group, The Institute of Metal Physics, Urals Division of the Russian Academy of Sciences, 18 S. Kovalevskaya Str. Yekaterinburg 620041, Russia
New effective methods for probing of phase transitions under pressure are steadily developed. Thus, simultaneous measurements of traditional X-ray diffraction and the electrical resistivity of a sample [1] were found to be more effective than those performed separately. A surface nanoindentation of a material also can bring some information concerning phase transitions under pressure [2].
In this work a new combined technique consisting in simultaneous measurements of electronic and mechanical properties is reported as a tool for probing of phase transitions under pressure. The electronic properties include the electrical resistance and the thermoelectric power. A technique of their measurements under pressure was reported earlier (e.g. [3]). A variation in mechanical properties of a material under pressure application may be related to phase transitions. Thus, a volumetric effect during a transition as well as a change in the compressibility in a high-pressure phase may be revealed by investigation of a material contraction. At surface nanoindentaion the phase transitions were noticed by pop-out and bend anomalies in load-displacement curves [2]. Meanwhile, a direct measurement of a contraction of the whole sample under pressurization inside an anvil cell remains challenging. In this work we report a technique that permits direct measurement of displacement of an anvil (plunger) under pressurization with assistance of an electronic dilatometer with a sensitivity of about 7.5 µV/nm. Then if a sample is compressed directly between anvils one can in-situ observe anomalies in a sample’s contraction. Advantages and disadvantages of this method are discussed. Several examples (Ce, CeNi, Bi2Te3, GaAs, ZnO, ZnSe, Si, and some others) of the technique application are displayed.
The research was supported by the Russian Foundation for Basic Research (RFBR).
[1] A.Yu. Kuznetsov, V. Dmitriev, Y. Volkova, A. Kurnosov, N. Dubrovinskaya, and L. Dubrovinsky, High Press. Res. 27, 213 (2007).
[2] V. Domnich, Y. Gogotsi, S. Dub, Appl. Phys. Lett. 76, 2214 (2000). [3] S.V. Ovsyannikov, V.V. Shchennikov, G.V. Vorontsov, A.Y. Manakov, A.Y. Likhacheva, V.A. Kulbachinskii, J. Appl. Phys. 104, 053713 (2008).
* E-mail :[email protected]
Keywords: phase transition, pressure, compressibility, thermopower
130
Composite fabric pressure cell for a SQUID magnetometer
G. Giriat*, K. V. Kamenev
School of Engineering & Centre for Science at Extreme Conditions, University of Edinburgh, Edinburgh, UK
Magnetic susceptibility is one of the key parameters characterising magnetic properties of materials and its accurate measurements have become routine with the introduction of magnetometers based on a superconducting quantum interference device (SQUID). Adding pressure as a clean way of tuning magnetic properties of material required the creation of pressure cells for the SQUID magnetometers. There has been several designs reported in the past 10 years of both piston-cylinder and opposed anvil types.
However all of these pressure cells have one major limitation - they perform well in dc susceptibility measurements but are not suitable for ac measurements. This is due to the Eddie currents set in the metallic body of the cell. Measurements show that for frequencies higher than 10 Hz the screening effect of the currents set in the cell can obscure the sample significantly.
To overcome this problem we designed a hybrid pressure cell made with use of advanced composite fabric[1]. The fabric forms the body of the cell and the end parts, located away from the sample and the pick-up coils of the SQUID, are made of BeCu. The BeCu/fabric interface shape has been optimized using finite element analysis method and is shown to withstand the stress resulting from a sample pressure of 20 kbar. The pressure cell is transparent to oscillating magnetic field in the whole range of frequencies and has a very low magnetic background in dc measurements.
Fig. 1. Composite pressure cell. The dot (red) shows the sample position. 1-End part -BeCu; 2-Core; 3- Zylon fibre reinforcement; 4- Zylon fabric; 5- Single layer of Zylon fibre; (Dimensions are in mm).
[1] D. Naik, S. Sankaran, B. Mobasher, S. Rajan, J.M. Pereira, Int. J. Impact Eng. 1,1 (2009).
*Email : [email protected]
Keywords : Pressure cell; Composite material; SQUID magnetometer; ac susceptibility.
131
Toroidal diamond anvils
I.A. Trojan and M.I. Eremets
Max-Planck-Institut für Chemie, Postfach 3060, 55020 Mainz, Germany
We modified diamond anvils by making a deepening in the culet and a toroidal groove around (Fig. 1). This geometry can be considered as a combination of beveled diamond anvil which allows high pressure to be achieved with toroidal or cupped large volume cells [1] which provide an enhanced pressure volume. We machined the deepening and the groove with the aid of focused ArF excimer 193 nm laser.
Fig. 1. Left- top view of diamond anvil with a deepening in the center and a toroidal groove. (b) Profile of toroidal diamond anvils. The anvils of diameter 400 μm are beveled at 8.5°.
These diamond anvils gave us an immediate advantage in the sample volume. For the cell shown in Fig1b the thickness of the sample was ≈14–15 μm estimated as the sum of the depths of the cavities in the diamonds ≈5–6 μm and the residual thickness of the gasket at megabar pressures. Typically, this thickness is 3–5 μm with the flat culets. We tested this cell to 150 GPa by measuring X-ray diffraction from nitrogen in situ with laser heating [2]. We achieved 250 GPa in experiments of X-ray diffraction of nitrogen with toroidal cell of 40 μm diameter of culet. Thus toroidal anvils work at least to the same pressures as typical anvils with flat culets while much higher volume is achieved. The increase of volume and the thickness of the sample is crucial for laser heating experiments: the heated sample is well separated from diamond anvils, which are extremely efficient thermal sinks, and therefore higher temperatures can be achieved. An enhanced volume of the sample also allows for lower X-ray diffraction accumulation time and makes experiments with light elements - such as nitrogen which is weakly scattering X-rays - possible. The diamond anvil’s “toroid” also opens a possibility for neutron diffraction measurements at megabar pressures. We tested the cells with metallic (typically rhenium) and cBN/epoxy gaskets. The cBN/epoxy gasket provides an enhanced thickness and is nearly transparent for X-ray. This provides new opportunities: X-ray and neutron diffraction in direction perpendicular to the exiting beam, and also performing electrical and other transport measurements which require electrical leads. The toroidal cells are also suitable for optical, in particular, Raman measurements. The toroidal shape apparently provides more uniform hydrostatic pressure in the sample. Stresses inside the anvil are also different in comparison with the conical anvil, and therefore the pressure scale based on the shift of high-frequency edge of Raman spectrum of the stressed diamond should be modified.
[1] L.G. Khvostansev, V.N. Slesarev, and V.V. Brazhkin. High Pressure Research, 24, 371 (2004) [2] I.A. Trojan, et al., Appl. Phys. Lett. 93, 091907 (2008)
* E-mail : [email protected] Keywords toroidal anvils, high pressure, neutron scattering
132
Hydrostatic limits of 11 pressure transmitting media
S. Klotz*, J.C. Chervin, P. Munsch, G. Le Marchand
IMPMC, CNRS, Université P. et M. Curie, 140 rue de Lourmel, 75015 Paris
We present a systematic and comparative study of the pressure-induced solidification of 11 frequently used pressure transmitting fluids using the ruby-fluorescence technique [1]. These fluids are: 1:1 and 5:1 iso-n pentane, 4:1 deuterated methanol-ethanol, 16:3:1 deuterated methanol-ethanol-water, 1:1 FC84-FC87 Fluorinert, Daphne 7474, silicone oil, as well as nitrogen, neon, argon, and helium. The data provide practical guidelines for the use of these fluids in high pressure experiments up to 50 GPa.
The measurements were carried out in a diamond anvil cell (DAC) loaded with 5-10 ruby spheres of ~3-5 m diameter immersed in the pressure transmitting medium under investigation. We determined the standard deviation of the pressures indicated by the ruby spheres as a function of average pressure, similar to previous investigations [2,3]. This quantity is shown to be a very sensitive indicator for the onset of pressure gradients. We also determined the pressure dependence of the R1-line width and the R1-R2 splitting. Our findings confirm in general the more recent work based on x-ray diffraction indicators [4,5]. Of importance for the high pressure community is the result on the 16:3:1 ethanol-methanol-water mixture which is shown to have essentially the same hydrostatic pressure range than the 4:1 mixture, as well as the findings on solid N2, Ne, Ar, and He.
[1] S. Klotz, J.-C. Chervin, P. Munsch, G. Le Marchand, J. Phys. D: Appl. Phys. 42, 075413 (2009).
[2] G.J. Piermarini, S. Block, J.D. Barnett, J. Appl. Phys. 44, 5377 (1973). [3] P.M. Bell and H.-K Mao, Carn. Inst. of Washington Year Book vol. 80, 404 (1981). [4] R.J. Angel, M. Bujak, J. Zhao, G.D. Gatta, S.D. Jacobsen, J. Appl. Cryst. 40, 26 (2007). [5] K. Takemura and A. Dewaele, Phys. Rev. B 78, 104119 (2008).
*E-mail : [email protected]
Hydrostaticity, pressure transmitting media, DAC, ruby fluorescence
133
High-pressure hydrogen storage for on-board applications and for coupling renewable energies to the electric grid
F. Darkrim Lamari*1, B. Weinberger1, N. Fagnon1, N. Girodon-Boulandet1, R. Batisse2, L. Briottet3, P. Langlois1
1CNRS LIMHP, Université Paris 13, Villetaneuse, France 2GDF SUEZ, CRIGEN, Saint-Denis la Plaine, France
3CEA LITEN, Grenoble, France.
Hydrogen, as an energy vector, stands as a feasible, viable alternative to the current dual challenge posed by energy security concerns on one hand and greenhouse gas limitations themselves linked to climate change concerns on the other. When considered for storage, its implementation, such as to evaluate the performance of materials either as adsorbents or as containers, may rely on specific high-pressure devices that permit evaluating these materials under operating conditions. High-pressure technological advancement will therefore continuously be required in that domain for the years to come.
For on-board (i.e. vehicular) hydrogen storage applications, four main approaches are currently investigated : high-pressure compression, cryo-compression (liquid hydrogen), absorption on hydrides, and adsorption on porous solids. We focused on the adsorption approach that typically relates to materials exhibiting high specific areas (1000-3000 m
2.g
-1)
and microporous volumes (1-2 cm3.g
-1)[1]. For this purpose, we designed and built a novel,
still unique device, operating under pressures up to 70 MPa, in which various carbon materials produced by different academic partners have already been characterized[2-3]. The results show that narrow microporosity is a key factor for achieving high storage capacities. For renewable energy sources such as wind or photovoltaic, the major drawback, which strongly limits their penetration, relates to their inherent variability. Energy storage systems, such as pressurized hydrogen gas in dedicated pipeline sections possibly acting as a buffer storage for coupling to the electric grid on demand, have the potential for addressing this problem. For that purpose, we are redirecting, in terms of larger pressure variations, the use of a test bench previously designed and built for testing realistically damaged pipe sections, in the operating conditions of hydrogen gas transmission pipelines and in relation with defect failure assessment models, either under monotonic loading up to 30 MPa or under cyclic loading between 4 and 10 MPa[4].
[1] M. Lamari, A. Aoufi, P. Malbrunot, AIChE J. 46, 632 (2000). [2] F. Darkrim, J. Vermesse, P. Malbrunot, D. Levesque, J. Chem. Phys. 110 4020 (1999). [3] M.A. de la Casa-Lillo, F. Lamari-Darkrim, D. Cazorla-Amorós, A. Linares-Solano, J. Phys.
Chem. B 106, 10930 (2002). [4] R. Batisse, A. Cuni, S. Wastiaux, L. Briottet, P. Lemoine, G. de Dinechin, C. Chagnot, F.
Castilan, V. Klosek, P. Langlois, D. Vrel, N. Girodon-Boulandet, B. Weinberger, IGRC 2008 (6th Int. Gas union Research Conf.), Paris, October 8-10, 2008.
*E-mail : [email protected]
Keywords: Hydrogen; Adsorption; Energy Storage; Renewable Energy.
134
Implantation of pressure-temperature sensors and conductive electrodes in diamond anvils (i-anvils): first results
H. Bureau1*, S. Kubsky2, F. Datchi1, P. Munsch1, C. Gondé3, G. Simon1, B. Couzinet1, J.C. Chervin1, F. Nicolas2, L. Delbecq4, C. Boukari4, C. Bachelet4, F. Bouamrane5,
T. Bouvet5, J. Meijer6, M. Burchard7 1IMPMC, Université P. et M. Curie, CNRS,, Paris, France
2Synchrotron SOLEIL, Gif sur Yvette, France 3ISTO, Orléans, France
4CSNSM, IN2P3, Orsay, France 5U.M.R. CNRS/Thales, Palaiseau, France
6RUBION, Ruhr Universität Bochum, Germany 7Ruprecht-Karls Universität Heidelberg, Germany.
“Intelligent anvils” (i-anvils) allow in situ pressure (P) and temperature (T) measurements in experiments using a diamond anvil cell (DAC) [1, 2]. Boron and carbon micro-structures are implanted in the diamond anvil lattice a few micrometers below the surface, the sensors are located a few μm below the center of the diamond culet (sample chamber position). When conductive electrodes are implanted at the position of the sample chamber on the culet of the anvil, instead of P,T sensors, they allow in situ measurements of electrical properties of the loaded sample at high P,T conditions in a DAC. The principle consists of applying an electrical potential across the structures through external contacts placed on the slopes of the anvil. The resistivity of these structures is sensitive to pressure and temperature applied in the sample chamber. The electrical transport properties of the sample can be measured the same way when electrodes have been implanted on the culet. Provided that calibrations have been previously performed, P and T can be measured in situ during experiments. I-anvils were prepared by implantation of B and C ion beams in diamond anvils at the ARAMIS (CSNSM, Orsay) and RUBION (Bochum) facilities. We used copper micro-stencil-masks designed on purpose and prepared at Thales/CNRS using LIGA technologies. Annealing and external connections of the i-anvils have been prepared at The Surface Laboratory of SOLEIL Synchrotron. The diamonds were mounted in a specially designed DAC inspired from the Bassett, Chervin and Burchard-Zaitsev DAC’s *3,4,5+ (see Munsch et al., this volume). In situ calibrations have been performed. T calibration were made at room pressure (RP) against Ktype thermocouples attached to the i-anvil and through melting point measurements of well known chemical components loaded in the DAC (S2, NaNO3, CsCl, NaCl). P calibrations have been performed at room temperature (RT) using ruby as pressure gauge [6]. Results show that T sensors are reliable; they allow a precise knowledge of temperature into the sample chamber during an experiment. P sensors have been found to be reliable too at constant RT. Preliminary P calibration results obtained at 100°C are promising; they suggest that pressure measurements are possible at high temperature providing it remains constant. In situ electrical measurements are in progress.
[1] A.M. Zaitsev, M. Burchard, J. Meijer, et al. Phys. Stat. Sol. 185, 59 (2001). [2].H. Bureau, M. Burchard, S. Kubsky, et al., J. Meijer. High Pres. Res. 26, 251 (2006). [3] W.A.Bassett, A.H. Shen, M. Buckum, Rev. Scientific. Instr. 64, 2340 (1993). [4] J.C. Chervin, B. Canny, J.M. Besson, Ph. Pruzan. Rev. Sci. Instrum. 66, 2595 (1994). [5] M. Burchard, A.M. Zaitsev, W. Maresh, Rev. Scient. Instr. 74, 1263 (2003). [6] J.C. Chervin, B. Canny, M. Mancenelli, High Pres. Res., 21, 305 (2002). *E-mail : [email protected] Keywords: diamond anvil cells, pressure, temperature, conductivity
135
A new diamond anvil cell for in situ spectroscopy study of geological fluids
P. Munsch1*, H. Bureau1, B. Couzinet1, A Somogyi2, E. Foy3, G. Simon1, S. Kubsky2, J.C. Chervin1
1 IMPMC, Université P. et M. Curie, CNRS, Paris, France 2Synchrotron SOLEIL, Gif sur Yvette, France
3LPS, CEA Saclay, France.
In situ study of crust and upper mantle geological fluids require the use of diamonds anvils cells suitable for equilibrium conditions of that fluids under pressure (from few hundred MPa to over ten GPa) and under temperature (from room temperature to 1500°C ideally). In order to quantify the chemical transfers of elements between geological fluids (aqueous fluids, silicate melts, supercritical fluids) by X-ray, Raman and Infrared spectroscopy a new diamonds anvils cell has been developed. The design of this new cell has been inspired by advantages of different existing cells. The first one is the membrane cell [1] in which you can put either two standard diamond anvils, or one standard diamond anvil and a thin diamond window (~ 500μm) for low energy X-ray fluorescence experiments [2].
Following the Basset hydrothermal cell [3] design, furnaces have been mounted on each anvil’s seat to externally heat each diamond; an inert gas flow system has been put to prevent high temperature oxidation. The installation of an internal water cooling and electrical connexions for diamonds in which pressure and temperature sensors are implanted (ianvils, see Bureau & al. this volume) have been inspired by the Burchard-Zaitsev cell [4].
The new cell allow in situ XRF, XRD, FTIR and Raman characterisation of fluids of geological nature in their equilibrium conditions inside the crust and the upper mantle. XRF analysis obtained in Basset hydrothermal diamond anvil cell and with the new cell will be presented, compared and discussed.
[1] J.C. Chervin, B. Canny, J.M. Besson, Ph. Pruzan. Rev. Sci. Instrum. 66, 2595 (1994). [2] P. M. Oger, I Daniel, A Picard, Biochimica et Biophysica Acta, Proteins and Proteomics,
1764, 434 (2006). [3] W.A.Bassett, A.H. Shen, M. Buckum, Rev. Scientific. Instr. 64, 2340 (1993). [4] M. Burchard, A.M. Zaitsev, W. Maresh, Rev. Scient. Instr. 74, 1263 (2003).
*E-mail : [email protected] Keywords: diamond anvil cells, in situ X-rays analysis, spectroscopy
136
Electrical characterization of a quartz crystal in high pressure CO2 by impedance analysis
M. Cassiède*1, J. Pauly1, J.H. Paillol2, J.-L. Daridon1 1Laboratoire des Fluides Complexes – UMR 5150 – B.P. 1155 – 64013 Pau Cedex, France
2Laboratoire de Génie Electrique – Hélioparc Pau-Pyrénées – 64053 Pau Cedex 9
Quartz crystal microbalance (QCM) is a very accurate sensor for measuring small changes of mass of thin films spread on the quartz surface. Under certain conditions, the mass of the deposited film is directly related to the variation of the resonance frequency according to the Sauerbrey’s equation. Thus, the resonance frequency of quartz can be used for monitoring the mass change caused by solvent adsorption or dissolution inside the film. In particular, this technique was extensively used to measure low gas solubilities in polymer films. However, when a quartz crystal is immersed in a high pressure non-inert gas, various effects such as pressure, viscosity, roughness on the surface of the quartz, adsorption of gas or even gas film formation slipping at the solid-gas interface can influence the resonance frequency of the quartz crystal and consequently complicate the relation between mass and frequency changes.
In order to determine experimentally such effects in the case of a quartz crystal in contact with carbon dioxyde in the neighbourhood of the critical conditions, the resonance curve of the quartz crystal under gas pressure was examined with a network analyzer which allows determining both resonance frequency and half-band–half width on various overtones.
The experimental device consists in an autoclave cell designed to resist to pressures as high as 100 MPa. The cell can accomodate two QCM composed of a thin quartz strip sandwiched between two metallic electrodes. Each of them is connected throw high pressure electric contacts to a network analyser. The polished AT-cut quartz crystals used in this work vibrate in the thickness shear mode, at different fundamental frequencies 0 f ranging between 3 and 10 MHz.
Some experiments have been carried out up to 50 MPa to determine the behaviour of the quartz microbalance under gaseous and supercritical CO2. Then, the theoretical impedance curves are fitted to the experimental data in order to determine the RLC parameters of the Butterworth-van-Dyke equivalent circuit. We present the results obtained from a fitting procedure that uses the literature values for the density and the viscosity of CO2 [1]. We also explain the deviation from the theoretical values by the monolayers of gas physically adsorbed on the electrodes or slipping on the surface of the resonator [2].
[1] R. Lucklum, P. Hauptmann, Measurement science and technology 15, 1854 (2003) [2] C. D. Stockbridge, Vacuum microbalance techniques 3, 147 (1966)
*E-mail : [email protected] Keywords : Quartz crystal microbalance, High pressure CO2, Viscosity loading
137
Raman spectroscopy study of nitromethane in a shear diamond anvil cell
P. Hébert1*, A. Isambert2, J.P. Petitet3 and A. Zerr3 1CEA, DAM, LE RIPAULT, Monts, France 2Université Paris 7 – IPGP, Paris, France
3LPMTM, CNRS UPR 9001, Université Paris-Nord 13, Villetaneuse, France
A detailed description of the reaction mechanisms occurring in shock-induced decomposition of condensed energetic materials is very important for a comprehensive understanding of detonation. Besides pressure and temperature effects, shear stress has also been proposed to play an important role in the initiation and decomposition mechanisms [1,2]. Static high pressure experiments in Diamond Anvil Cells (DAC) are usually carried out to study the behaviour of energetic materials at detonation pressure and to get insights into the first steps of the initiation. In such experiments, the compression is quasi-hydrostatic and it is thus difficult to study precisely the effect of shear stress. In order to do so, a Shear Diamond Anvil Cell (SDAC) has been developed [3]. It is actually a classical DAC with a function that allows the upper diamond anvil to rotate about the compression axis relative to the opposite anvil.
In this paper, we present a Raman spectroscopy study of the effect of shear stress on the highpressure behaviour of nitromethane. Two major effects of shear stress are observed in our experiments. The first one is a lowering of the pressures at which the different structural modifications that nitromethane undergoes are observed. The second effect is observed at 28 GPa. At this pressure, a sudden decomposition of the sample occurs just after shear application. Observation of the sample after decomposition shows the presence of a black residue which is composed of carbon as indicated by the Raman spectrum.
[1] Manaa, M. R., Fried, L. E., and Reed, E. J., Journal of Computer-Aided Materials Design 10, 75 (2003).
[2] Kuklja, M.M. and Rashkeev, S.N., Applied Physics Letters, 90, 15913 (2007). [3] Blank, V. D. and Zerr, A. J., High Pressure Research, 8, 567 (1992).
*E-mail : [email protected] Keywords : shear diamond anvil cell, nitromethane, Raman spectroscopy
138
139
Advances in Large Facilities Techniques
Lectures The extreme conditions beamline at PETRA III, DESY: Possibilities to conduct
time resolved monochromatic and pink beam diffraction experiments in
laser heated DAC. _________________________________________________ 141
Melting in the diamond anvil cell using energy dispersive XAS ____________________ 142
Time-of-flight single-crystal neutron diffraction to 10 GPa _______________________ 143
Three dimensional X-ray diffraction study of MgGeO3 post-perovskite plastically
deformed at 80 GPa _______________________________________________ 144
X-ray FEL applications in extreme states of matter research _________________ 145
Application of charged particle beams of TWAC-ITEP accelerator for diagnostics
of high dynamic pressure processes __________________________________ 146
Current status of the high pressure neutron study at J-PARC _____________________ 147
Development of a new multi-purpose high pressure XRD, density and viscosity
measurements setup at beamline ID27 of the ESRF _____________________ 148
Posters LF 01 : High pressure local structural changes in amorphous and crystalline
GeO2 ____________________________________________________________ 149
LF 02 : Pressure-induced symmetry reduction in zircon-type orthovanadates ________ 150
LF 03 : The new MAR555 flat pannel detector at the high pressure diffraction
beamline ID09A __________________________________________________ 151
LF 04 : X-ray absorption study of hard ReB2 under high pressure __________________ 152
LF 05 : Simultaneous x-ray density and acoustic velocity measurements of
titanium dioxide __________________________________________________ 153
LF 06 : In-situ X-ray experiments using Diamond/SiC composite anvils prepared
with hot isostatic pressing (HIP) _____________________________________ 154
LF 07 : Pressure–Temperature phase diagram of strontium titanate SrTiO3 _________ 155
LF 08 : Rotational Paris-Edinburgh Cell for Single-Crystal Neutron Scattering ________ 156
LF 09 : A Drive for Changing Pressure in-situ in a Large Volume Pressure Cell for
Low Temperatures Neutron Scattering ________________________________ 157
LF 10 : Gas loading apparatus for Paris-Edinburgh cells _________________________ 158
LF 11 : Pressure Cell for Inelastic Neutron Scattering ____________________________ 159
LF 12 : Plasticity and stress in gold: application for high pressure experiments ______ 160
LF 13 : Energy Dispersive X-ray Absorption Spectroscopy applied to studies at
extreme conditions ________________________________________________ 161
LF 14 : High-Resolution Single-Crystal Neutron Diffraction to 10GPa at ILL __________ 162
LF 15 : Combining high pressure and coherent diffraction: a first feasibility test _____ 163
LF 16 : Next generation portable large volume high-P/T/stress cells at ESRF for
extreme chemistry, materials and Earth sciences _______________________ 164
140
141
The extreme conditions beamline at PETRA III, DESY: Possibilities to conduct time resolved monochromatic and pink beam
diffraction experiments in laser heated DAC.
H.-P. Liermann*1, W. Morgenroth2, A. Berghäuser3, A. Ehnes1, B. Winkler2, H. Franz1, E. Weckert1
1Deutsches Elektronen Synchrotron (DESY), Hamburg, Germany 2Department of Crystallography, University of Frankfurt, Frankfurt, Germany
3Department of Mineralogy, University of Hamburg, Hamburg, Germany.
Powder x-ray diffraction experiments in laser heated diamond anvil cells (DAC) have been a standard experimental technique used at all 3
rd generation extreme condition synchrotron
facilities over the last decades. However, the combination of single crystal diffraction at simultaneous high-pressure and –temperature using a laser heated DAC has not been realized. This is in part because single crystal diffraction pattern created by monochromatic beam can only be collected on an area detector when the sample within the DAC is rotated, resulting in the obstruction of the laser heating beam. However, rotations of the sample can be eliminated when one uses pink beam Laue diffraction.
In this work we describe the design of the “Extreme Conditions Beamline P02.2” at PETRA III, Hamburg, Germany, that will be used to conduct both monochromatic (8-70 keV) and pink beam diffraction experiments. Attention will be drawn to the pink beam capabilities of the station and the alternate use of monochromatic and pink x-ray beams and the possibility to conducted single crystal diffraction in the laser heated DAC. We will discuss the different stages of the beamline development and the high-pressure experimental techniques that we like to offer once commissioning of the beamline is completed. The possibility of conducting time resolved experiments in the dynamic DAC
[1] and the pulsed laser heated DAC
[2] in
conjunction with fast choppers will be discussed as well as the possibility to shade light on the nature of transient phase stages occurring during phase transition at simultaneous high-pressures and -temperatures.
[1] Evans WJ, Yoo CS, Lee GW, Cynn H., Lipp MJ, Visbeck K Rev. Sci. Inst. 78, 073904 (2007). [2] Goncharov AF, Beck P, Struzhkin VV, Hemley RJ and Crowhurst JC J. Phys. Chem. Solids 69
2217 (2008).
* E-mail: [email protected] Keywords: Extreme Conditions Research, Diamond Anvil Cell, Laser Heating, 3
rd Generation
Synchrotron
142
Melting in the diamond anvil cell using energy dispersive XAS
G. Aquilanti1,2, A. Trapananti1, R. Boehler3
1Sincrotrone Trieste, 34012 Basovizza Trieste, Italy 2ESRF, 6 rue Jules Horowitz 38043 Grenoble, France
3Max-Planck-Institut für Chemie, Postfach 3060, D-55020 Mainz, Germany
Science at extreme pressure conditions in diamond anvil cells (DAC) historically represents one of the main applications of energy dispersive x-ray absorption spectroscopy (EDXAS) and is well documented in the literature. However, applying pressure is not sufficient for studying chemical properties of matter or to have access to its different states: solid and liquid. Laser-heating in the diamond anvil cell has shown to be applicable for many fields of research ranging from mineral physics, to material synthesis through the study of basic physical and chemical properties in the high P-T regime. In this contribution we show the first melting XAS data in a laser heated DAC recorded at the beamline ID24 of the ESRF. The specific advantages of EDXAS for melting in the DAC using the laser heating techniques will be highlighted. Two examples will be shown: molten iron and germanium at Megabar pressures.
*E-mail : [email protected] Melting, EDXAS, laser heated DAC
143
Time-of-flight single-crystal neutron diffraction to 10 GPa
C.L. Bull*1, H. Hamidov1, M. Guthrie1♦, K. Komatsu1♠, M.J. Gutmann2, M. W. Johnson1,2, J. S. Loveday1 and R.J. Nelmes1
1SUPA, School of Physics and Astronomy, Centre for Science at Extreme Conditions, University of Edinburgh EH9 3JZ U.K
2ISIS Facility, Rutherford Appleton Laboratory, OX11 0QX, U.K.
We have successfully developed techniques for single-crystal data collection up to 10 GPa on the time-of-flight (ToF) Laue diffractometer, SXD, at the UK’s ISIS pulsed neutron source, using Paris-Edinburgh (PE) and other pressure cells, and thus reach well beyond the long-established limit of ~2 GPa for high-resolution single-crystal studies using neutrons. We have developed a mount to place the sample accurately on the beam centre, and the precise, tight, incident-beam collimation needed to limit background from the fast-neutron flux. The pressure-cell mount also provides for cooling down to 20 K. Methods have been developed to centre samples that cannot be accessed optically (inside opaque anvils) and maintain centring. ToF data collection makes use of fixed area detectors surrounding the sample position, and high-pressure studies – in which sample lattice parameters are often unknown – give rise to a special need for full calibration of the detectors (i) to measure lattice parameters very accurately and (ii) to determine the precise directions of diffracted beams in order to make corrections for attenuation by the cell. We have devised a calibration method, and have implemented procedures to correct for the wavelength dependent attenuation.
ToF Laue techniques allow many reflections to be measured in parallel, and a full data set can be collected from systems like KDP and DKDP (KH2PO4, KD2PO4) and squaric acid (H2C4O4) in relatively short times around three days. This provides advantages for solving structures to medium resolution and following structural changes with temperature and pressure. The SXD spectrum also provides a high flux of short wavelength neutrons, and thus the ability to collect reflections to short d-spacings of ~0.35 Å. But the fast neutron background is high in this range, and – unlike monochromatic data collection – ToF methods are inefficient at collecting key reflections for a long time to improve statistics.
We will present these ToF techniques and developments, and successful studies of KDP, DKDP and squaric acid up to 10 GPa, and also studies of ice VI and squaric acid at high pressure and low temperature. Results reveal that hydrogen bond centring is a progressive, gradual change rather than an abrupt transition – a good example of a study requiring a range of pressure greater than the ~2 GPa previously available.
On-going projects include the development of a device for gas-loading into the PE cells (details in another presentation: see A. Bocian, K. V. Kamenev et al), and attempts to take single-crystal studies using both gem and sintered-diamond anvils to higher pressures. Both are designed to extend the range of accessible science. Our programme at ISIS is greatly aided by an on-site laboratory we have created, with the support of ISIS, for development of gaskets, anvils and in-situ growth of crystals from liquids.
*E-mail : [email protected] Current address: Advanced Photon Source, Argonne National Laboratory, South Cass Ave,
Argonne, Illinois, U.S.A. Current address: Laboratory for Earthquake Chemistry, University of Tokyo, Japan
Keywords: Single-crystal, hydrogen bonding, neutron diffraction
144
Three dimensional X-ray diffraction study of MgGeO3 post-perovskite plastically deformed at 80 GPa
C. Nisr*1, G. Ribarik2, T. Ungar2, G. Vaughan3, P. Cordier1, S. Merkel1 1Laboratoire de Structure et Propriétés de l’Etat Solide, CNRS, Université Lille 1
59655 Villeneuve d’Ascq, France 2Department of General Physics, Eötvös University, Budapest, Hungary
3ESRF, Grenoble, France
Mechanicals properties of materials are strongly affected by microscopic defects such as dislocations. For high pressure materials that can not be quenched to be studied with Transmission Electron Microscopy (TEM), X-ray line profile analysis become a very useful method for characterizing dislocations [1,2].
The goal of this study is to apply the X-ray line profile analysis technique to study the dislocations and single crystal properties of MgGeO3 post-perovskite, an analogue of MgSiO3 (one of the main constituents of the D” layer in the interior of the earth), deformed in a Diamond Anvil Cell (DAC) at about 80 GPa.
MgGeO3 post-perovskite can not be made as single crystals, which are required for the line profile analysis. It lead us to use three dimensional X-ray diffraction (3DXRD) [3,4,5,6] for characterizing individual grain within polycrystals. This technique allows the extraction of position, orientation and elastic and plastic strain for several hundred grains simultaneously.
On ID11 at ESRF, the DAC is fixed to a sample stage that allows a ω-rotation around a vertical axis with a step of Δω. We focus a monochromatic high-energy X-ray beam perpendicular to the rotation axis and collect diffraction patterns with Δω=0.25 Data are collected on a detector close to the sample for indexation of the grains and a set of detectors in far position to obtain high resolution single crystals diffraction peaks.
At each ω value, grains with different orientation will give rise to diffraction spots that may appear or disappear with changes in ω. These spots enable us to identify individual grains within the polycrystal.
Once grains are indexed, information can be deduced. Positions and crystallographic orientations of each grain can be fitted. We can also look at characteristic orientations between grains, and characterize strain tensors.
When diffraction spots will be indexed, we will be able to correlate them with positions on the high resolution detector and start the evaluation of single-crystal X-ray diffraction patterns in terms of dislocations density and character. This will reveal critical information about the plastic properties of post-perovskite.
[1] W. Yuming, L. Shansan, L. Yenchin, J. Appl. Cryst. 15, 35 (1982). [2] T. Ungar, M. Leoni, P. Scardi, J. Appl. Cryst. 32, 290 (1999). [3] H.F. Poulsen, S. Garb, T. Loretzen, D. Juul Jensen, F. W. Poulsen, N. H. Andersen, T. Frello,
R. Feidenhans, H. Graafsma, J. Synchrotron Rad. 4, 147 (1997). [4] D. Juul Jensen, A. Kvick, E. M. Lauridsen, U. Lienert, L. Margulies, S. F. Nielsen, H. F.
Poulsen, Mat. Res. Soc. 590, 227 (2000). [5] L. Margulies, G. Winther, H. F. Poulsen, Science. 291, 2392 (2001). [6] E. M. Lauridsen, S. Schmidt, R. M. Suter, H. F. Poulsen, J. Appl. Cryst. 34, 744 (2001).
*E-mail : [email protected]
145
X-ray FEL applications in extreme states of matter research
T. Tschentscher
European XFEL, c/o DESY, Notkestrasse 85, 22607 Hamburg, Germany
X-ray free-electron lasers (FEL) will provide intense, ultrashort and high brilliance radiation in the photon energy regime of few 100 eV up to ~14 keV. Based on the self-amplified spontaneous emission principle one obtains transverse coherent x-ray radiation, pulse durations shorter 100 fs and intensities of order 10
12 photons per pulse. While first lasing has
been achieved [1] for hard x-rays, first experiments are expected to be carried out still this year. Currently the LCLS in Stanford, U.S.A., is commissioned, the SPring-8 FEL and the European XFEL are under construction and further facilities are in the planning phase [2].
X-ray FEL radiation has interesting properties for the investigation of extreme states of matter. The high brilliance, intensity and short pulse duration make this radiation suitable for probing matter during dynamical processes, e.g. during the compression using pulsed laser radiation. One can further use the intense x-ray pulses to excite matter volumetrically and isochorically thus enabling very high values of temperature and pressure. Ideas and possible configurations for FEL experiments for extreme states of matter research will be discussed. Using the FLASH facility providing soft x-ray FEL radiation at 97 eV photon energy first experiments heating solid aluminum to temperatures of several eV have been carried out [3]. Results of these experiments will be discussed.
[1] P. Emma et al., Proc. of the Particle Accelerator Conf., (2009) [2] see e.g. the websites for LCLS (lcls.slac.stanford.edu); Spring-8 XFEL
(www-xfel.spring8.or.jp) and European XFEL (www.xfel.eu) [3] B. Nagler et al., Nature Phys., in print (2009)
E-mail: [email protected]
146
Application of charged particle beams of TWAC-ITEP accelerator for diagnostics of high dynamic pressure processes
S.A. Kolesnikov*1, A.A. Golubev2, V.S. Demidov2, S.V. Dudin1, A.V. Kantsyrev2, V.B. Mintsev1, G.N. Smirnov2, V.I. Turtikov2, A.V. Utkin1 , B.Y. Sharkov2, V.E. Fortov2
1IPCP RAS, Chernogolovka, Russia 2SSC RF – ITEP, Moscow, Russia
Radiographic study of matter using charged particle beams is the unique experimental technique for absolute measurements of important material characteristics of dense non-transparent objects in superhigh-speed high dynamic pressure processes. The 800-MeV proton radiography facility for high dynamic pressure studies of condensed matter has been developed at the Terrawatt Accellerator of Institute of Theoretical and Experimental Physics (TWAC-ITEP) recently. The magnetic optics system of facility
[1] consists
of 7 magnetic quadrupole lenses of ML-15 type whose purpose is to prepare the proton beam for the transmission through studied object and to form an image of the object after that. The proton beam intensity of TWAC-ITEP accelerator is about 10
10 particles per pulse. A single
proton beam bunch with the duration of 800 ns consists of four consequent 70 ± 5 ns long micro bunches with 250 ± 15 ns intervals between them. It potentially enables the registration of up to four proton radiography images of studied processes during a single accelerator cycle. High-speed CCD cameras with the synchronization with a single proton bunch from accelerator were used for this aim. Static experiments with the variety of test objects were conducted with the aim of determining the spatial resolution of facility. The measured resolution amounted to 0.30 ± 0.01 mm in current experimental arrangement. First dynamic experiments were conducted on the facility. The explosive techniques were used for the generation of high dynamic pressures in studied samples which were placed in specially designed explosive containment chamber during the experiments. The processes of ejecta formation on shock loaded uneven steel surface and a propagation of detonation waves in small pressed TNT charges were studied. The series of pairs of radiographic images of shock loaded samples shot for two consecutive proton bunches with the duration of 70 ns separated by 250 ns were obtained in these experiments. Axial density profiles calculated from detonating TNT images show good quantitative agreement with the data on the known parameters and simulation results for a detonation of the same TNT charges in the rarefaction zone. It shows the principal possibility of the use of proton radiography technique as a method for absolute density measurements in shock wave and detonation studies. However, an improvement of resolution capacity of radiographic facility is needed for full-scale studies of superhigh-speed high dynamic pressure processes in condensed matter. The appropriate work on its modernization and optimization is being conducted at the moment. This work is supported by grants of Grant Council of President MK-5426.2008.2, RFBR 07-02-01396-a and RosAtom contract N.4e.45.03.09.1061.
[1] A.A. Golubev, V.S. Demidov, E.V. Demidova, M.M. Kats, S.B. Kolerov, V.S. Skachkov, G.N. Smirnov, V.I. Turtikov, A.D. Fertman, and B.Yu. Sharkov, Atomic Energy, 104, 134 (2008).
147
Current status of the high pressure neutron study at J-PARC
K. Komatsu*1, T. Hattori2, H. Arima3, J. Abe2, M. Arakawa1, T. Okuchi4, H. Kagi1, W. Utsumi2, T. Yagi5
1Geochemical Laboratory, Univ. of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan 2Quantum Beam Science Directorate, Japan Atomic Energy Agency,
Tokai, Ibaraki, 319-1195, Japan 3J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki, 319-1195, Japan
4ISEI, Okayama Univ., 827 Yamada, Misasa, Tottori 682-0193 Japan 5ISSP, Univ. of Tokyo, Kashiwa, Chiba 277-8581, Japan
We and many co-workers have made a constant effort to the designing and constructing for a neutron diffractometor beamline for high pressure science at the Japan Proton Accelerator Research Complex (J-PARC). After the first neutron production at J-PARC Materials & Life Science Experimental Facility (MLF) on 30
th May 2008, the commissioning of the beamlines in
MLF is energetically progressing. As our target is widely ranged across the scientific discipline, the beamline should realize not only diffraction but also scattering and radiography from powder and liquid/glass samples under wide pressure/temperature conditions. In order to satisfy such a demand, we planned to use several types of high pressure devices. In particular, new opposed-anvil cells with a nano-polycrystalline diamond [1] and a large press with cubic multi anvils are specific feature of the high pressure beamline [2]. Another characteristic of the beamline is a focusing non-parallel supermirror guide, which makes a large divergence of the incident beam and produce 1.0 x 10
8 n/s/cm
2 of the neutron flux at the sample position
[3].
Although the beam flux was much weaker than the designed one (1MW), we managed to measure diffraction patterns from Pb sample (Φ 3~6mm x t3mm) in two types of high pressure devices - Paris-Edinburgh cells and Palm-cubic cells - on the Engineering Materials Diffractometer “TAKUMI” in MLF. The TAKUMI beamline has a relatively long flight path with a curved supermirror guide, i.e. 40 m of the moderator-sample distance and 2 m of sample-
detector distance, which allows us to take diffraction patterns with a resolution of d/d = 0.15%-0.4% (adjustable by slits) [4]. According to the high resolution, the TAKUMI beamline has an advantage for the complex material with a large unit cell or strain measurements under high pressure. For the use under higher pressure on the TAKUMI beamline, we designed a 1m long focusing supermirror to put just upstream to the sample position. This focusing device has a pair of the mirror upper and lower side of the guide, which only focus neutrons vertically and less affect to the resolution. Here we report the design of the high pressure beamline in J-PARC, the results of the high pressure experiments and the test experiment of the focusing device for the TAKUMI beamline.
[1] T. Irifune et al., Nature 421, 599 (2003). [2] W. Utsumi et al., Nucl. Instr. and Meth. A 600, 50 (2009). [3] H. Arima, et al., Nucl. Instr. and Meth. A 600, 71 (2009). [4] S. Harjo et al., Mater. Sci. Forum. 524-525, 199 (2006).
* E-mail : [email protected] Keywords J-PARC, high pressure neutron diffraction
148
Development of a new multi-purpose high pressure XRD, density and viscosity measurements setup at beamline ID27 of the ESRF
M. Mezouar*, J.P. Perrillat, G. Garbarino, S. Bauchau
ESRF, BP220, 38000 Grenoble
The simultaneous collection of high quality X-ray diffraction data, density and viscosity at high pressure and high temperatures is very important in various domains of research such as geosciences or materials science. However, the practical realization of such multi-purpose device is very challenging. We present such a development at beamline ID27 which is based on the newly developed VX5 Paris-Edinburgh press. The press is interfaced to newly developed Soller slits and imaging systems to measure high quality diffraction patterns and high resolution X-ray images of the sample assembly. The press is mounted on an optimized 2 circle diffractometer which allows to move the press upside down in order to perform viscosity measurements using the falling sphere method. The potential of this new development will be illustrated on some school case examples.
* E-mail : [email protected] Keywords: Paris-Edinburgh press, X-ray diffarction, X-ray imaging, viscosity
149
High pressure local structural changes in amorphous and crystalline GeO2
M. Vaccari*, G. Aquilanti, S. Pascarelli, O. Mathon
European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, 38043 Grenoble, France
The nature of amorphous-amorphous transformations (AATs) under pressure and the concept of polyamorphism in the classic network-forming glasses represent a strongly debated issue in modern condensed matter physics. Although amorphous GeO2 (a-GeO2) is one of the most studied materials undergoing an AAT at high pressure, conflicting results were obtained in previous works and – despite two decades of experimental and theoretical investigations – the detailed pressure evolution of germanium local environment is far from being clarified. Therefore, a new in situ high pressure EXAFS investigation of a-GeO2 (and, for comparison purposes, quartz-like crystalline q-GeO2) has been performed [1] at BM29 beamline of ESRF. Pressure up to 13 GPa was obtained through a large volume Paris-Edinburgh press. The pressure evolution of the Ge-O distance and coordination number, as well as the absorption edge position, allowed us to monitor the details of the phase transition. In the low-pressure range (below about 5 GPa) both q- and a-GeO2 undergo possible deformation and rotation of GeO4 tetrahedra, while the Ge-O bond does not experience any average compression. The tetrahedral to octahedral structural transformation in q-GeO2 is quite sharp and located at about 8.5 GPa (although at least the full 6-12 GPa pressure range should be considered as the transition region), while in a-GeO2 it is instead continuous and gradual and the full octahedral state is not reached at 13 GPa as commonly believed. Although the contemporary presence of tetrahedra, pentahdra and octahedra cannot be excluded in the whole transition region, no evidence is provided of the recently claimed intermediate state with a constant average coordination of five in the 6-10 GPa pressure range. Finally, a continuous breakdown of intermediate range order in glassy GeO2 is observed up to about 10 GPa. This work sheds new light into a highly-debated subject and contributes to a deeper understanding of the mechanisms underlying the AAT in glassy GeO2.
[1] M. Vaccari et al., J. Phys.: Condens. Matter 21, 145403 (2009)
*E-mail : [email protected]
150
Pressure-induced symmetry reduction in zircon-type orthovanadates
D. Errandonea1,3,*, R. Lacomba-Perales1,2, J. Ruiz-Fuertes1,2, A. Segura1,2, S. N. Achary4, and A. K. Tyagi4
1Malta Consolider Team 2Departamento de Física Aplicada-ICMUV
3Fundación General de la Universidad de Valencia (Spain) 4Chem. Division, Bhabha Atomic Research Centre (India)
We report room-temperature ADXRD studies on zircon-type EuVO4, LuVO4, and ScVO4. Experiments were performed up to 27 GPa using a DAC at the I15 beamline of Diamond. In the three compounds we found evidence of an structural transformation from the tetragonal zircon structure (I41/amd) to a tetragonal scheelite-type structure (I41/a). The onset of the transition is near 8 GPa, but the transition is sluggish and the low- and high-pressure phases coexist in a pressure range of about 10 GPa. In EuVO4 and LuVO4 a second transition to a monoclinic fergusonite-type phase (I2/a) was found near 21 GPa. The observed low- and high-pressure structures consist of AO8 (A = Eu, Lu, Sc) dodecahedra and BO4 tetrahedra. However, the phase transitions involve a gradual lowering of the point-group symmetry of the crystal from 4/mmm to 4/m and to 2/m. The first transformation is irreversible and has a first-order character while the second one is reversible and has a second-order character.
The EOS for the zircon and scheelite phases were also determined. It was established that zircon-type ScVO4 (B0 = 178 GPa) is less compressible than EuVO4 (B0 = 149 GPa) and LuVO4 (B0 = 166 GPa), being the most incompressible orthovanadate studied to date. We also found that, for each compound, the HP phase is at least 18% less compressible than the zircon-type one. In addition, we observed that the compression of the different phases is anisotropic, being the c-axis the less (more) compressible axes in zircon (scheelite). Furthermore, for both phases we determined a differential polyhedral compressibility, behaving the VO4 tetrahedra as rigid units and accounting the AO8 dodecahedra for most of the volume contraction. This fact is also related with the anisotropic compressibility of the low- and high-pressure phases. The sequence of structural transitions and the compressibilities will be discussed in comparison with other zircon-type oxides, in particular with geophysical relevant materials such as ZrSiO4.
*E-mail : [email protected]
151
The new MAR555 flat pannel detector at the high pressure diffraction beamline ID09A
M. Hanfland
European Synchrotron Radiation Facility, Grenoble, France
ID09A uses monochromatic diffraction with large area detectors on single crystals and powdered samples at high pressures in diamond anvil cells. It provides variable beam sizes
down to 10 x 10 m, to study samples from a few GPa to approximately 200 GPa at ~30 keV and very high photon fluxes of ~10
13/sec. It offers state of the art optical systems for
additional in situ characterization of the samples at high pressure (Raman, etc.) and a highly developed sample environment.
Recently the MAR345 online image plate reader was replaced by a MAR555 flat panel detector. Besides the obvious advantage, a few second readout time providing quasi real-time data collection for powder diffraction, a few minutes for acquiring a complete single crystal data set, the new detector has doubled the angular resolution, 0.025° compared to 0.05°, see Fig. 1. It has an excellent dynamic range, 18 bit compared to 16 bit, and considerably improves the stability and accuracy of the experimental setup, no moving parts, no distortions. Examples of the use of the new detector in powder and single crystal diffraction will be given.
Fig. 1: Powder diffraction pattern of LaFeO3 with He as pressure transmitting medium at 8.4 GPa measured with the MAR555 flat panel detector. The resolution has almost doubled compared to the MAR345 image plate reader. The splitting of reflections due to the orthorhombic distortion is now clearly observable (see insert).
*E-mail : [email protected]
202
022
152
X-ray absorption study of hard ReB2 under high pressure
J. Pellicer-Porres1, A. Segura1, A. Muñoz2, A. Polian3, A. Congeduti4 1MALTA Consolider Team, ICMUV, Universidad de Valencia, Valencia (Spain)
2MALTA Consolider Team, Universidad de La Laguna, Tenerife, Spain 3Institut de Minéralogie et de Physique des Milieux Condensés, Paris, France
4Synchrotron SOLEIL, Saint-Aubin, France
The quest of superhard materials has recently focused attention on ReB2. Following recent results [1] this compound would combine the properties of high hardness, low compressibility and resistance to high differential stress. The extraordinary properties of ReB2 have been attributed [1-2] to the combination of a high electron density together with the formation of a network of strong, covalent bonds.
High pressure is a versatile tool that can be used to characterize the effect of altering the electron density and to explore the changes induced in covalent bonding. This idea was present in the original work of Chung et al. [1], where the compressibility of the lattice parameters and bulk modulus of the material was measured by x-ray diffraction (XRD) experiments under high pressure. However, no information about the behavior of the covalent bonds under high pressure was given.
XRD under high pressure presents experimental limitations (like, for example, diamond absorption, preferential orientation or low statistics) which make the extraction of information from the intensity of diffraction reflections not always straightforward. This is particularly the case in ReB2, due to the large atomic number difference between Re and B. On the opposite, x-ray absorption (XAS) is a local technique which directly probes the local environment of the absorbing atom. In this work we have performed XAS measurements under high pressure at the Re-L3 edge which give direct access to the Re-B bondlength. The EXAFS analysis yields the average Re-B bond compressibility, which results 5.6(9)x10
-4 GPa
-1.
Combining this information with previous x-ray diffraction experiments we have characterized the network of covalent bonds responsible of the rigidity of the structure. The main conclusion is that the compression is anisotropic and non homogeneous, reflecting bonding differences between Re-B and B-B bonds and also between not equivalent Re-B bonds. The layer defined by boron atoms tend to become flatter under high pressure. The measured angular distortions are of the same order of magnitude than those of ionic semiconductors.
[1] H. Y. Chung, M. B. Weinberger, J. B. Levine, R.W. Cumberland, A. Kavner, J. M. Yang, S. H. Tolbert, and R. B. Kaner, Science 316, 436 (2007).
*2+ X. Chen, C. L. Fu, M. Krˇcmar, and G. S. Painter, Phys. Rev. Lett. 100, 196403 (2008).
*E-mail : [email protected] Keywords: XAS, high pressure, superhard, ReB2.
153
Simultaneous x-ray density and acoustic velocity measurements of titanium dioxide
A. Kantor*1,2, L. Dubrovinsky1, V. Prakapenka2, I. Kantor2, S. Sinogeikin2
1Bayerishes Geoinstitut, University of Bayreuth, Germany 2GSECARS, University of Chicago, USA
Brillouin scattering is an interaction of light photons with acoustic or vibrational phonons. The interaction consists of an inelastic scattering process in which a phonon is either created (Stokes process) or annihilated (anti-Stokes process). The energy of the scattered light is slightly changed, that is decreased for a Stokes process and increased for an anti-Stokes process. This shift, known as the Brillouin shift, is equal to the energy of the interacting phonons. The energy of acoustic phonons in the material is related to the sound velocity - one of the most important geophysical characteristics of a mineral. If sound velocities and density are measured simultaneously the elastic constants and moduli can be calculated. At high pressures (using diamond anvil cell - DAC) such experiments can be performed at the Advanced Photon Source – APS (Sector 13, BMD-station) [1].
It was reported [2] that nanocrystalline anatase (TiO2) undergoes amorphous-amorphous transition at about 20 GPa during decompression. In order to prove this transition and see how it is pronounced in the sound velocities behavior, we performed a high-pressure experiment in a diamond anvil cell. The cell was prepared for x-ray diffraction and Brillouin spectroscopy simultaneous experiments.
The amorphization of nanocrystalline material was well-pronounced during compression of the sample and occurs at about 18 GPa, according to the x-ray diffraction data, but there was no drastic changes in peak position during decompression.
Collected Brillouin spectra (a representative one find in Fig. 1) allowed calculating the sound velocities pressure dependencies of both bulk VP and Vs. After pressure-induced amorphization both sound velocities are changing smoothly during compression and decompression and no elastic discontinuities were observed.
Fig. 1. A Brillouin spectrum, collected from the nanocrystalline TiO2 at 15.4 GPa in a diamond anvil cell.
[1] S. Sinogeikin, J. Bass, V. Prakapenka, D. Lakshtanov, G. Shen, C, Sanchez-Valle, M. Rivers, Rev. Sci. Inst. 77, 103905 (2006).
[2] V. Swamy, A. Kuznetsov, L. Dubrovinsky, P. McMillan, V. Prakapenka, G, Shen, B. Muddle, Phys. Rev. Let. 96, 135702 (2006).
*E-mail : [email protected] Keywords: Brillouin Spectroscopy, High Pressure, Nanomaterials, Titanium Dioxide
154
In-situ X-ray experiments using diamond/SiC composite anvils prepared with hot isostatic pressing (HIP)
O. Ohtaka1*, K. Funakoshi2, T. Kikegawa3, A. Suzuki4, M. Shimono5 1Earth and Space Science, Osaka University, Toyonaka 560-0043, Japan
2SPring-8/JASRI, Hyogo 679-5198, Japan 3Photon Factory, Institute of Material Science, Tsukuba 305-0801, Japan
4Earth and Planetary Science, Tohoku University, Sendai 980-8578, Japan 5Material Chemistry, Ryukoku University, Ohtsu 520-2123, Japan
Diamond/SiC composites were synthesized from diamond and Si powders using a hot isostatic pressing (HIP) technique. Cubes of the composites with 14 and 26 mm edge length were thereby fabricated, and an application to the second stage anvils in a Kawai-type high-pressure apparatus was attempted [2,3]. Because the diamond/SiC composites are transparent to X rays, the present anvils are applicable not only to energy dispersive diffraction experiments but also to angle dispersive diffraction experiments and radiographic studies that need a larger window for X-ray passes.
[1] Shimono and Kume, J. Am. Ceram. Soc., 87, 752 (2004). [2] Ohtaka et al., PEPI, 143-144, 587 (2004). [3] Ohtaka et al., High Pressure Research, 25, 11, (2005).
* E-mail : [email protected] Keywords: diamond composites, multianvil press, in-situ X-ray studies, X-ray radiography,
Figures Angular dispersive X-ray diffraction image recorded through diamond/SiC anvils (left). CCD image of sample chamber in a high pressure cell (right).
155
Pressure–Temperature phase diagram of strontium titanate SrTiO3
M. Guennou*, P. Bouvier and J. Kreisel
Laboratoire des Matériaux et du Génie Physique, CNRS-Grenoble Institute of Technology, MINATEC, 3 parvis Louis Néel, 38016 Grenoble, France.
Strontium titanate (SrTiO3, STO) has been the object of constant attention for more than 40 years, both at very low temperatures for its quantum paraelectric behaviour and at higher temperatures for its ferroelastic antiferrodistortive (AFD) transition. At ambient conditions STO is cubic and its AFD transition to a tetragonal structure can be induced by decreasing temperature or increasing pressure. The temperature-induced transition has been intensely studied, both experimentally and theoretically, and is regarded as an archetype of a soft-modedriven phase transition. At ambient pressure, this transition occurs at 105 K and can been accurately described within the Landau theory framework of phase transitions by a 246 potential corrected for quantum saturation effects[1,2]. However, some questions in the Landau-type description remain unanswered due to the still limited number of data collected in the P-T phase diagram. Especially, the pressure dependence of the coupling parameter between the order parameter and the spontaneous strain, directly related to the shape of the phase boundary in the P-T phase diagram, is under question. Moreover, the possibility of a further phase transition to an orthorhombic phase at higher pressure has been suggested[3] but not yet confirmed.
In this work, we investigate the phase transition of SrTiO3 under high pressure by means of Raman spectroscopy and X-ray diffraction. The former is carried out at room temperature up to 23 GPa and is confronted to previous results[3,4]. XRD using synchrotron radiation at the ESRF has been performed at room temperature, 108°C and 194°C up to 50, 30 and 26 GPa respectively. This new set of data enables us to reconsider the cubic-tetragonal transition line in the P-T phase diagram and to rule out a further phase transition to an orthorhombic phase within the investigated pressure range.
[1] S. A. Hayward and E. K. H. Salje, Phase Transitions 68, 501 (1999). [2] M. A. Carpenter, American Mineralogist 92, 307 (2007). [3] A. Grzechnik, G. H. Wolf and P. FA. McMillan, J. of Raman Spectroscopy 28, 885 (1997). [4] T. Ishidate and T. Isonuma, Ferroelectrics 137, 45 (1992).
*E-mail : [email protected] Keywords : SrTiO3, XRD, Raman scattering, phase transition
156
Rotational Paris-Edinburgh cell for single-crystal neutron scattering
J. Fang*1, K. V. Kamenev1, C. L. Bull2, J. S. Loveday2, R. J. Nelmes2 1School of Engineering & Centre for Science at Extreme Conditions,
University of Edinburgh, Edinburgh, UK 2School of Physics & Centre for Science at Extreme Conditions,
University of Edinburgh, Edinburgh, UK
Paris-Edinburgh (PE) press is a compact device to produce high-pressure conditions in large volume samples for neutron-scattering experiments. So far, several modifications of the cell have been developed for crystallographic studies and for research into chemical bonding properties and geophysical liquid evolution
[1-7].
We report the development of a compact rotational apparatus based on the V4 type PE press. It consists of central rotatable modules and a side drive structure as illustrated in Fig. 1. This allows the sample to be rotated with respect to the cell body while under load. This provides a solution to the problem of either the incident or diffracted beams in a single crystal diffraction experiment being obscured by the tie-rods of the press and hence increases the volume of reciprocal space that can be accessed. The design has been developed for the experiments on the D9 Single Crystal Diffractometer at Institute Laue-Langevin, France. The drive capability, total deformation, stress distribution and control precision are analysed for the load of up to 150 tons.
[1] J. M. Besson, G. Weil, G. Hamel et al. Phys. Rev. B 45, 2613 (1992). [2] J. M. Besson, Ph. Pruzan, S. Klotz et al. Phys. Rev. B 49, 12540 (1994). [3] J. M. Besson, R. J. Nelmes. Phys. B 213&214, 31 (1995). [4] S. Klotz, J. M. Besson, G. Hamel et al. Appl. Phys. Lett. 66, 1735 (1995). [5] S. Klotz, G. Hamel, J. Frelat, High Press. Res. 24, 219 (2004). [6] C. L. Bull, M. Guthrie, S. Klotz et al. High Press. Res. 25, 229 (2005). [7] G. D. Bromiley, S. A. T. Redfern, Y. Le Godec et al. High Press. Res. (accepted)
*E-mail : [email protected] Paris-Edinburgh Cell; High pressure; Neutron scattering; Single crystal
Fig. 1 A 3D assembly view of the compact rotational Paris-Edinburgh press showing the drive structure accommodating a step motor, a gearbox with high transmission ratio and two pinions (on the left) and the central rotatable shafts: top shaft and bottom shaft (on the right).
157
A drive for changing pressure in-situ in a large volume pressure cell for low temperatures neutron scattering
N. Suresh1, J. P. Attfield2 and K.V. Kamenev1 1Centre for Science at Extreme Conditions and School of Engineering,
University of Edinburgh, Edinburgh UK 2Centre for Science at Extreme Conditions and School of Chemistry,
University of Edinburgh, Edinburgh UK
Neutron diffraction at high pressure has progressed over the years and the experimental facilities have promoted its application for the solution of various physical problems with extreme sample environments. In most of the low-temperature high-pressure neutron scattering techniques that are available at present[1,2] the pressure cell has to be removed from its cryogenic environment for each pressure change. This results in the need to re-centre the sample in the beam to get a consistent diffraction data collection. Also for low temperature experiments the time required to warm up to room temperature and to cool down for each pressure step takes time and consumes liquid helium. Therefore the allocated beam time is not utilised efficiently.
We undertook a task to resolve this difficulties and to design a system that would allow pressure change at low temperatures without the need to warm up the pressure cell or remove it from the cryostat. Similar systems based on either mechanical[3] or membrane drive[4] exist for small diamond anvil pressure cells. The challenge we had to overcome is that for large sample volume required for a neutron scattering experiments a significant load needs to be transmitted to the pressure cell. For this we are developing a technique to facilitate a drive mechanism for applying the load smoothly while the cell is mounted inside the cryostat. We use Finite Element Analysis (FEA) to model the design of the modified Dubna cell[5] in order to adapt it to the driving mechanism which is based on the Bowden cable[3]. The materials selected for the system have to withstand both the load and the low temperature.
[1] D.B. McWhan, D. Bloch, G. Parisot, 1974, Rev. Sci. Instrum., 45, 643. [2]V.I. Aksenov, A.M. Balagurov, S.L.Platonov, B.N. Savenko, V.P. Glazkov, V.I. Naumov,
V.A. Somenkov and G.F. Syrykh, High Pressure Res., 1995,14, 181. [3] D.J. Dunstan, and W, Scherrer Rev. Sci. Instrum. 1988, 59, 627. [4]R. LeToullec, J.P. Pinceaux and P. Loubeyre, 1988, High Pressure Res. 1, 77. [5] Glazkov V P and Goncharenko I N 1991, High Pressure Phys. Tech. 1, 56 (in Russian)
*E-mail : [email protected] In-situ pressure change; neutron diffraction; FEA modeling
158
Gas loading apparatus for Paris-Edinburgh cells
A. Bocian1*, K. V. Kamenev1, C. L. Bull2, J. S. Loveday2, R. J. Nelmes2 1School of Engineering & Centre for Science at Extreme Conditions,
University of Edinburgh, Edinburgh, UK 2School of Physics & Centre for Science at Extreme Conditions,
University of Edinburgh, Edinburgh, UK
Paris-Edinburgh cell [1] is a widely used large-volume opposed-anvil pressure cell for neutron scattering. Up until now it has been successfully used with a number of solid and liquid samples and pressure media. However, so far there is no reliable technique developed for loading gases into sample volume. The only known method is a cryogenic loading of liquid gases. However this technique cannot be used with some gases such as helium or hydrogen.
The ability to load gases at room temperature would bring several benefits. It would allow us to study any gas or gas mixture under high pressure. It would also make it possible to replace liquid pressure transmitting media with gases in order to achieve more hydrostatic compression conditions.
Here, we will present a gas loading device for Paris-Edinburgh cell. A special collar holding Paris-Edinburgh cell anvils and a pressure vessel have been designed. The collar with anvils and gasket are placed into the vessel, which allows us to introduce gas under pressure of up to 140 MPa into the sample volume and compress the anvils to seal the gas enclosed within the gasket. The anvils with the sealed gasket are then placed into Paris-Edinburgh cell for further compression and neutron scattering measurements.
[1] J. M. Besson et al., Physica B 1992 180-181, 907. [2] R. L. Mills et al., J. Chem. Phys. 1975 63, 4026.
*E-mail : [email protected] Keywords: Paris-Edinburgh cell, gas loading device, neutron diffraction
Fig. 1 Neutron diffraction pattern of nitrogen loaded at 130 MPa and compressed up to 4 GPa. The phase transition to solid state expected at 2.4 GPa [2] can be clearly seen in the data. Lead was used as a pressure calibrant.
159
Pressure cell for inelastic neutron scattering
W. Wang*1, D. A. Sokolov2, A. Huxley2, K. V. Kamenev1 1School of Engineering & Centre for Science at Extreme Conditions,
University of Edinburgh, Edinburgh, UK 2School of Physics & Centre for Science at Extreme Conditions,
University of Edinburgh, Edinburgh, UK
Compared to neutron diffraction, inelastic scattering experiments typically require an order of magnitude longer data collection times for the same sample size and sample environment
[1].
We present the design of the piston-cylinder pressure cell optimised by the means of finite element analysis in order to minimize the attenuation. The plug with electric feed-through and manganin pressure sensor enables the accurate monitoring of pressure in the whole range of temperatures. The novel design of the pressure seal eliminates the need in the teflon capsule providing more space for the sample. The cell is made of non-magnetic materials and is capable of reaching the pressure of 2 GPa.
[1] S. Klotz, M. Braden and J.M. Besson, Hyperfine Interactions 2000, 128 , 245
*E-mail : [email protected] Inelastic neutron scattering; Finite element analysis; High-pressure cell design
160
Plasticity and stress in gold: application for high pressure experiments
S. Merkel1*, C. Tomé2, H.R. Wenk3, P. Cordier1 1Laboratoire de Structures et Propriétés de l'Etat Solide, CNRS, Université Lille 1, France
2Materials Science and Technical Division, Los Alamos National Laboratory, USA 3Department of Earth and Planetary Science, University of California, Berkeley, USA
For many years, the interpretation of lattice strains measured on samples plastically deformed in the diamond anvil cell has been a controversial issue. In fact, understanding the link between single crystal elasticity and rheology, microstructure, and polycrystalline behavior is fundamental for modeling and interpreting material properties. We have shown how elasto-plastic self-consistent (EPSC) models of can be used to assess the development of internal elastic strains within grains of a sample plastically deformed up to high pressure [1]. The EPSC model is compared to results of radial diffraction experiments. It is used to simulate the macroscopic flow curves and internal strain development within a polycrystal. Input parameters are single crystal elastic moduli and their pressure dependence, critical resolved shear stresses and hardening behavior of slip and twinning mechanisms.
Here, we study the development of stress in Au plastically deformed in the diamond anvil cell. A comparison between experimental and EPSC model results allows us to identify and characterize microscopic deformation mechanisms that control the plastic behavior of Au. We also obtain information on stress, both at the microscopic (grain) and macroscopic level (polycrystal).
Results we obtain are then used to assess the development of stress in various experimental conditions and quantify stress level depending on the deformation geometry. For instance, we will show that hydrostatic compressions can give rise to internal stresses. Influence of temperature on stress relaxation will also be discussed.
[1] S. Merkel, C.N. Tomé, H.R. Wenk, A modeling analysis of the influence of plasticity on high pressure deformation of hcp-Co. Phys. Rev. B, 79, 064110 (2009)
*E-mail : [email protected]
161
Energy dispersive X-ray absorption spectroscopy applied to studies at extreme conditions
S. Pascarelli1, G. Aquilanti2, O. Mathon1, M. Muñoz3, A. Trapananti2,4 and M. Ruffoni1 1European Synchrotron Radiation Facility, Grenoble, France
2Sincrotrone Trieste, Trieste, Italy 3Université Joseph Fourier, Grenoble, France
4Universitá di Camerino, Camerino, Italy
Energy Dispersive X-ray Absorption Spectroscopy (EDXAS) is now a well-established method which has been applied to a broad range of applications. The energy dispersive spectrometer employs a bent crystal to focus and disperse a diverging polychromatic X-ray beam onto the sample. The beam passing through the sample then diverges towards a position sensitive detector, where beam position is correlated to energy. Major advantages of this scheme are: i) an intrinsic stability in focal spot position and in energy scale, since during acquisition the optics is not scanned ii) a high acquisition speed, where all energy points are acquired rigorously in parallel and iii) a small focal spot, thanks to the focusing properties of the curved crystal.
In this presentation I will make an overview of recent results obtained on the EDXAS beamline ID24 at the ESRF, in diverse areas of science at extreme conditions. Examples will cover the structure of molecular solids at Megabar pressures [1], magnetoelastic coupling in 3d metals [2] and more recent developments that are now opening the way to in-situ investigations of chemical reactions that occur in the interior of planets [3-5]. I will then briefly mention new developments for the study of melts at extreme conditions [6] and warm dense matter [7].
[1] A. San Miguel, H. Libotte H., M. Gauthier, G. Aquilanti, S. Pascarelli, and J.P. Gaspard, Physical Review Letters 99, 015501 (2007)
[2] S. Pascarelli, M. P. Ruffoni, A. Trapananti, O. Mathon, G. Aquilanti, S. Ostanin, J. B. Staunton, and R. F. Pettifer, Physical Review Letters 99, 237204 (2007)
[3] M. Muñoz, S. Pascarelli, G. Aquilanti, O. Narygina O, A. Kurnosov, and L. Dubrovinsky, High Pressure Research 28, 665 (2008)
[4] G. Aquilanti, S. Pascarelli, O. Mathon, M. Muñoz, O. Narygina and L. Dubrovinsky, J. Synchrotron Rad. in press
[5] D. Andrault, M. Muñoz, N. Bolfan-Casanova, N. Guignot, J.P. Perrillat, G. Aquilanti and S. Pascarelli, submitted
[6] R. Boehler, H.G. Musshoff, R. Ditz, G.Aquilanti, and A. Trapananti, Rev. Sci. Instr. 80, 045103 (2009)
[7] Collaboration with P. Loubeyre and F. Occelli (CEA, Paris).
*E-mail : [email protected] Keywords: X-ray Absorption Spectroscopy, EXAFS, XANES, XMLD
162
High-resolution single-crystal neutron diffraction to 10 GPa at ILL
C.L. Bull*1, H. Hamidov1, M. Guthrie1 , K. Komatsu1 , E. Gregoryanz1, M-T. Fernandez-Diaz2, J. Archer2, R.J. Nelmes1 and J.S. Loveday1
1SUPA, School of Physics and Astronomy, Centre for Science at Extreme Conditions, University of Edinburgh EH9 3JZ, U.K
2Institut Laue-Langevin, 6, rue Jules Horowitz. 38042 Grenoble France
Until recently, high-resolution single-crystal neutron diffraction measurements at high pressure were limited to a pressure of ~2 GPa which was first achieved more than 20 years ago. This limit arises from the relatively large sample size required (3mm
3), which requires a
relatively large pressure which is difficult to incorporate into single-crystal procedures, particularly for a monochromatic angle-dispersive experiment where the cell must be mounted onto a diffractometer which orients the cell for each reflection. We have now successfully used the new, relatively compact, VX Paris-Edinburgh (PE) cells
[1] on the D9
diffractometer at the ILL, and it is possible to collect high-resolution data at pressures up to at least 10 GPa. We have constructed a mount and devised procedures to align and centre the sample; we have built collimation to maximize signal:background; and we have developed procedures to rotate the cell avoiding collisions. Further developments in progress include a rotating-anvil device to allow collection of reflections obscured by the columns of the PE cell (details in another presentation: see J. Fang, K. V. Kamenev et al).
Monochromatic techniques offer advantages for problems which can be solved by collecting specific layers or lines of reflections, or where a starting structural model can be used to select the reflections most sensitive to the structural issue to be resolved. We have used these strategies and have also used the short wavelength capability of D9 (λmin=0.3 Å) to maximise the access to reciprocal space allowed by the restrictions of the pressure cell.
We will present these developments and a successful high-resolution study of squaric acid (H2C4O4) that shows the protons in the hydrogen bonds to be almost certainly distributed over two sites at 3.5 GPa — a pressure where Raman studies reported the H-bond to symmeterise
[2]. And we will summaries other studies and data collection to 10 GPa. Results
achieved illustrate the power of D9 and its ability to collect short d-spacing data — data have been collected down to 0.35 Å so far.
The ability to achieve pressures of 10 GPa now opens up a wider range of high-pressure problems, and use of gem-anvil cells to grow crystals in-situ and the introduction of gas-loading offer the prospect of further increasing the range of accessible science and the quality of data that can be obtained. Some studies are requiring the development of onsite facilities for sample loading and cell handling, and we will discuss this important aspect as well.
[1] S.Klotz, G.Hamel and J.Frelat, High Press. Res. 2004, 24, 219. [2] Y.Moritomo,T. Katsufuji , Y.Tokura, J. Chem. Phys. 1991, 95, 2244.
*E-mail : [email protected] Current address: Advanced Photon Source, Argonne National Laboratory, South Cass Ave,
Argonne, Illinois, U.S.A. Current address: Laboratory for Earthquake Chemistry, University of Tokyo, Japan
Keywords: Single-crystal, hydrogen bonding, neutron diffraction
163
Combining high pressure and coherent diffraction: a first feasibility test
D. Le Bolloc’h1, A. Polian2, J.-P. Itié3 and S. Ravy3 1Laboratoire de Physique des Solides, Université Paris-Sud, Orsay, France
2Physique des Milieux Denses, IMPMC, CNRS UMR 7590, Université P. et M. Curie,140 rue de Lourmel, 75015 Paris, France
3Synchrotron SOLEIL, L'Orme des merisiers, Saint-Aubin BP 48, 91192 Gif-sur-Yvette cedex, France
Coherent diffraction techniques provide a new insight into a wide variety of phenomenon. In particular, disordered samples which are coherently illuminated give rise to speckle pattern and the speckle fluctuations analysis gives access to the dynamic of fluctuations. As an example, coherent diffraction allows us to recently observe and analyze the central peak phenomenon in the close vicinity of a displacive phase transition in SrTiO3[1]. Obtaining such coherent beam is not always obvious mainly because of optical aberrations of beamlines. Nevertheless, the improvement of x-ray optical elements alloys us to obtained now good degree of coherence with a reasonable intensity.
It seems interesting to combine high pressure and coherent diffraction, providing a unique way to measure fluctuations under pressure. From an experimental point of view, the combination of both techniques is not obvious because the presence of a diamond anvil cell under the coherent beam may destroy the degree of coherence. We have performed a first experimental test taking care of the anvil cell geometry in order to reduce optical aberrations. We have measure how the coherent beam propagates through the diamond cell by studying how a rectangular slits diffraction pattern is disturbed by the diamond cell. Surprisingly, the shape of the cross-like pattern and the visibility of fringes remain almost unchanged [see figure below]. This observation is important because this opens the possibility of studying time fluctuations under pressure.
Diffraction of the direct beam by 5 µm x 5 µm slits located 2.2 m downstream the CCD detector, without sample (left) and through the sample and pressure cell.
[1] S. Ravy, D. Le Bolloc’h, R. Currat, A. Fluerasu, C. Mocuta, and B. Dkhil Phys. Rev. Lett. 98, 105501 (2007)
*E-mail : [email protected] Perovskite, coherent diffraction
164
Next generation portable large volume high-P/T/stress cells at ESRF for extreme chemistry, materials and Earth sciences
Y. Le Godec1*, G. Bromiley2,S-Y. Chien3, G. Hamel1, S. Klotz1, D. Martínez-García4, M. Mezouar5, J.P. Perrillat5, J. Philippe1, S.A.T. Redfern3 and V.L. Solozhenko6
1IMPMC, 140 rue de Lourmel, 75015 Paris, France 2University of Edinburgh, EH9 3JW, UK
3University of Cambridge, CB2 3EQ, UK, DFA 4University of Valencia, Valencia, Spain
5ESRF, Grenoble, France 6LPMTM-CNRS, Villetaneuse, France
We describe a recently developed portable large volume high-P/T/stress device installed at ESRF (beamline ID27) for extreme chemistry, materials and Earth sciences. The system uses the V7 type Paris-Edinburgh (PE) press. The V7 has a capacity of 450 tonnes but only a weight of less than 90 kg. The ~ 20% larger overall dimensions permit accommodation of various modules whose volume is too large to be incorporated in the “traditional” PE press:
1/ Multi-anvil module (T-cup)
The Stony Brook “T-cup system” is a miniaturised KAWAI-type apparatus which operates routinely to 25 GPa and 2500 K [1]. Our T-cup module has been widely modified from its original design in order to accommodate optimised Sollers slits and large area CCD detectors for angle dispersive X-ray diffraction [2].The novel feature of this apparatus is its extreme compactness, which provides important advantages compared to conventional multi-anvil cells.
2/ Rotational PE module (roPEc)
A small and portable rotational PE module (compatible with the V7 Paris-Edinburgh loading frame) has been developed [3], in which controlled torsional shear stresses can be applied between the opposed anvils, allowing high-P high-T measurements of samples subjected to a wide range of strain regimes (Cf. Figure). This apparatus effectively operates as a high-P/T torsional pendulum apparatus, and utilizes many of the inherent advantages of the high-T Paris-Edinburgh cell such as portability, large sample volume and flexibility in sample assembly design. Torsional shear is applied to samples by rotating one of the opposed anvils with respect to the other anvil, thereby ensuring that the effects of increased pressure and deviatoric stress are effectively decoupled. Large and variable shear stresses and strain rates can be imposed on samples held at simultaneous high P-T conditions. This roPEc module has been successfully combined with ADX and radiograph imaging in order to measure stress and strain in situ.
The reduced dimensions and weight permit easy exchange between the different modules and offer also the possibility of being able to work with several presses simultaneously, i.e. carry out experiments with one cell whereas other presses are being prepared for the following measurements. This avoids long on-line decompression times usually associated to conventional (non-compact) large volume press which lead to a considerable loss of beamtime.
[1] M.T. Vaughan et al., Rev. High Pressure Science and Technology, 7, 1520 (1998). [2] Y. Le Godec et al., accepted in Journal of Synchrotron Radiation (2009). [3] G. Bromiley et al., accepted in High Pressure Research (2009).
*E-mail : [email protected] Keywords : high pressure, high temperature, synchrotron, multi-anvils.
165
Geosciences
Lectures Indoor vs Outdoor Geophysics ______________________________________________ 167
Sound velocity measurements on Fe0.89Ni0.04Si0.07 to 108 GPa: mineral physics
constraints on the silicon abundance in the Earth’s core _________________ 168
Compressibility change in molten Fe and models of core formation _______________ 169
Mass-Radius Relations for Low-mass Exoplanets Comparing Different Equations
of State _________________________________________________________ 170
Crystallization and melting of minerals in-situ at high pressure ___________________ 171
Eutectic properties of primitive Earth’s magma ocean __________________________ 172
Ab initio Molecular Dynamics simulations of liquid fayalite (Fe2SiO4) at high
pressures. _______________________________________________________ 173
In situ viscosity measurements of liquid Fe-S alloys at high pressures ______________ 174
Posters GS 01 : Physicochemical transformation of Al and SiO2 powders mixture under
high pressure and modelling of the Earth’s interior _____________________ 175
GS 02 : High-pressure phase transitions in wüstite FexO _________________________ 176
GS 03 : Detection of the spinel–post-spinel transition in Fe3O4 by in situ electrical
resistivity measurements at high pressures and temperatures ____________ 177
GS 04 : High pressure electronic transition in hcp Fe and Fe0.9Ni0.1 _________________ 178
GS 05 : Molecular Dynamics Simulations of Oil Components at Geological
Conditions _______________________________________________________ 179
GS 06 : Single crystal structural refinement of high and low spin siderite up to
54 GPa __________________________________________________________ 180
GS 07 : A-cation effect on the compressibility of ACoF3 perovskites ________________ 181
GS 08 : High-pressure ferroelastic transition in K0.8Na0.2AlSi3O8 hollandite __________ 182
GS 09 : Pressure Effect on Upper-Mantle Rheology: Insights from Single-Crystal
Experimental Deformation at Mantle P and T __________________________ 183
GS 10 : Use of the Spark Plasma Sintering (SPS) technique in the preparation of
geological samples suitable for high-pressure experiments _______________ 184
GS 11 : Sound attenuation and dispersion in vitreous silica ______________________ 185
GS 12 : 5-coordinated silicon in Earth’s mantle materials ________________________ 186
166
167
Indoor vs Outdoor Geophysics
R.C. Liebermann*
Consortium for Materials Properties in Earth Sciences (COMPRES), Stony Brook, NY, USA
Research in mineral physics is essential for interpreting observational data from many other disciplines in the Earth Sciences, from geodynamics to seismology to geochemistry to petrology to geomagnetism to planetary science, and extending also to materials science and climate studies. The field of high-pressure mineral physics is highly interdisciplinary. Mineral physicists do not always study minerals nor use only physics; they study the science of materials which comprise the Earth and other planets and employ the concepts and techniques from chemistry, physics, materials science, and even biology
[1].
Observations from geochemistry and geophysics studies lead to the development of petrologic, seismic and geodynamical models of the Earth’s deep interior. The goal of mineral physics is to interpret such models in terms of variations of pressure, temperature, mineralogy/crystallography, and/or chemical composition with depth.
The discovery in 2004 of the post-perovskite phase of MgSiO3 at pressures in excess of 120 GPa and high temperatures has led to an explosion of both complimentary experimental and theoretical work in mineral physics and remarkable synergy between mineral physics and the disciplines of seismology, geodynamics and geochemistry. Similarly, the observation of high-spin to low-spin transitions in Fe-bearing minerals at high pressures has important implications for the lower mantle of the Earth.
We focus in this talk on the use of experimental physical acoustics to conduct “indoor seismology” experiments to measure sound wave velocities of minerals under the pressure and temperature conditions of the Earth’s mantle. This field of research has a long history dating back at least to the studies of Francis Birch in the 1950s. The techniques include ultrasonic interferometry
[2,3], resonant ultrasound spectroscopy, and Brillouin spectroscopy.
Many of these physical acoustic experiments are now performed in conjunction with synchrotron X-radiation sources at national and international facilities
[4,5].
[1] Liebermann, R. C., Transactions of American Geophysical Union, 40, pp. 365, 373, 2005. [2] Li, B., J. Kung, and R.C. Liebermann, Phys. Earth Planet. Interiors, 143-144, 559-574. [3] Higo, Y., T. Inoue, B. Li, T. Irifune and R. C. Liebermann, Phys. Earth Planet. Interiors, 159,
276-285, 2006. [4] Li, B., K. Woody, and J. Kung, J. Geophys. Res. 111, B11206, 2006. [5] Li, B., and R. C. Liebermann, Proc. National Acad. Sci., 104, 9145-9150, 2007
*Email : [email protected] Keywords: Mineral physics, sound velocities, ultrasonics, synchrotrons
168
Sound velocity measurements on Fe0.89Ni0.04Si0.07 to 108 GPa: mineral physics constraints on the silicon abundance in the Earth’s core
D. Antonangeli*1,2, J. Siebert1,2, J. Badro1, D.L. Farber2, F.J. Ryerson2, G. Fiquet1 1Institut de Minéralogie et de Physique des Milieux Condensés, UMR CNRS 7590,
Institut de Physique du Globe de Paris, Université Paris 6 et 7, Paris, France 2Lawrence Livermore National Laboratory, Livermore CA, USA
The composition of the Earth’s core is of fundamental interest in geosciences, and still a widely debated topic. The study of seismic wave propagation and normal mode oscillation are two of the most direct probe of the Earth’s interior. However, to derive accurate compositional and structural models, these seismic observations have to be combined with experiments constraining the density and elastic properties of highly compressed minerals and geophysically relevant elements. Specifically, starting from shock wave measurements, Birch proposed the Earth’s core to be made by iron alloyed with nickel and some “light element”, to account for the difference in the density between the core and pure iron[1]. Since then, several elements have been proposed, including silicon amongst the most likely candidates[2].
In this paper, we present sound velocity and density measurements on polycrystalline hcp Fe0.89Ni0.04Si0.07, compressed into a diamond anvil cell up to 108 GPa.
Polycrystalline homogeneous samples of silicon bearing iron-nickel alloy have been synthesized at high pressure and high temperature in a piston cylinder press. Silicon and nickel contents have been quantified by electron microprobe analysis.
Inelastic x-ray scattering (IXS) measurements have been performed on the ID28 beamline, at the European Synchrotron Radiation Facility. We collected data at 27, 37 and 47 GPa on quasi-hydrostatically compressed samples, and at 32, 73 and 108 GPa on nonhydrostatically compressed samples. At each investigated pressure point, we mapped the longitudinal acoustic phonon dispersion throughout the entire first Brillouin zone, deriving the aggregate compressional sound velocity from a sinus fit to experimental data[3]. To directly obtain density information, we also collect x-ray diffraction patterns.
The measured density dependence of the compressional sound velocity is compared to values obtained for pure iron[3,4] and Fe0.78Ni0.22 alloy[5]. While no systematic offsets can be observed between data on pure iron and iron-nickel alloy, the values measured for Fe0.89Ni0.04Si0.07 are systematically higher. Over the investigated pressure range, Fe0.89Ni0.04Si0.07 is ~9% faster then pure iron at the same density. Extrapolation to Earths’ core densities and comparison with seismic velocity and density profiles from PREM allow us to infer an inner core compositional model containing 4-5 wt% of Ni and about 2 wt% of Si[2].
[1] F. Birch, J. Geophys. Res. 1952, 57, 227. [2] J. Badro et al., Earth Planet. Sci. Lett. 2007, 254, 233. [3] D. Antonangeli et al., Earth Planet. Sci. Lett. 2004, 225, 243. [4] G. Fiquet et al., Science 2001, 291, 468. [5] A.P. Kantor et al., Phys. Earth Planet. Inter. 2007, 164, 83.
*Email : [email protected] Keywords: sound velocity, iron, light elements, Earth’s inner core
169
Compressibility change in molten Fe and models of core formation
C. Sanloup*1, W. van Westrenen2, H. Maynard3 and J.-P. Perrillat4 1Université Pierre et Marie Curie UMR7193 and Institut de Physique du Globe de Paris
UMR7154, Paris, France 2Faculty of Earth and Life Sciences, VU University, Amsterdam, The Netherlands
3CSEC and School of Physics, University of Edinburgh, Edinburgh, United-Kingdom 4European Synchrotron Radiation Facility, Grenoble.
Metallic Fe, in both solid and liquid state, is the dominant component of the cores of the terrestrial planets. Knowledge of its physical properties at high pressures and temperatures is critical for a wide variety of Earth Science and physics research fields ranging from magnetic field generation to cosmochemistry. However, crucial properties such as the equation of state of molten Fe have not been measured yet under static high pressure conditions.
We will present the first in situ density measurements of molten Fe up to 8 GPa by an X-ray absorption technique using high energy synchrotron X-ray radiation. A transition is identified by a compressibility change in the vicinity of the δ-γ-liquid triple point at 5.2 GPa. This transition provides a physical explanation for the marked modification in the pressure evolution of Ni partitioning between liquid metal and silicate[1]. The existence of a link between molten Fe polymorphism and element partitioning has profound implications for geochemistry. Core formation models indeed rely on the distribution of key trace elements such as Ni[2], while the nature and amount of light elements in planetary cores are largely determined from their affinity for liquid Fe[3].
[1] P. Kegler, A. Holzheid, D. J. Frost, D. C. Rubie, R. Dohmen, H. Palme D., Earth Planet. Sci. Lett. 2008, 268, 28.
[2] J. Li and C. Agee, Nature 1996, 381, 686. [3] J.-P. Poirier, Physics Earth Planet. Int. 1994, 85, 319.
*Email : [email protected] Keywords : Fe, liquid, Earth, core
170
Mass-radius relations for low-mass exoplanets comparing different equations of state
F. Wagner*1, F. Sohl1, H. Hussmann1, M. Grott1 1Institute of Planetary Research, German Aerospace Center (DLR),
Berlin-Adlershof, Germany
The field of planetary sciences is rapidly expanding due to the growing number and unexpected diversity of discovered planets beyond the solar system. Modeling the interior structures has now become a major task to classify and understand the global evolution of these new planets. Here we present a model approach used to calculate the pressure- and temperature-dependent density distribution within terrestrial and ocean exoplanets, ranging from 1 to 15 times the mass of the Earth. A relationship between radius R and mass M for
Earth-like planets according to R M0.269
has been established within a mass range of one to ten Earth masses. This result is in good agreement with scaling laws obtained by other authors[1,2,3]. A similar relationship is viable for similarly massive ocean planet with a Ganymede-like bulk composition.
A major uncertainty is due to the lack of experimental data to reliably parameterize equations of state (EOS) in the high-pressure range from 200 up to 10,000 GPa, which is the significant range of pressure at modeling massive Earth-like exoplanets. Therefore we have implemented different isothermal EOS into our model to compare their implications on the total mass and radius of the calculated exoplanets. The implemented EOS are (a) the Murnaghan’s integrated linear EOS[4], (b) the third-order Birch-Murnaghan EOS[5] based on the Eulerian finite strain, (c) a third-order Logarithmic EOS[6] constructed from the Hencky logarithmic strain, (d) the Vinet EOS[7,8] derived from the Rydberg interatomic potential, (e) a modified Polytropic EOS*9+ commonly applied in astrophysics, (f) the Stacey’s reciprocal K-primed EOS[10] based on the concept of the importance of the derivative of the bulk modulus in the limit of infinitely large pressure. Results indicate that the reciprocal K-primed EOS predicts systematically smaller radii of the model planets as the other EOS. Furthermore the impact of different bulk compositions on the studied EOS will be discussed.
*1+ D. Valencia, R. J. O’Connell, D. D. Sasselov, Icarus 2006, 181, 545-554. [2] C. Sotin, O. Grasset, A. Mocquet, Icarus 2007, 191, 337-351. *3+ D. Valencia, D. D. Sasselov, R. J. O’Connell, Astrophys. J. 2007, 665, 1413-1420. [4] F. D. Murnaghan, Proc. Nat. Acad. Sci. 1944, 30, 244-247. [5] F. Birch, J. Geophys. Res. 1952, 57, 227-286. [6] J.-P. Poirier, A. Tarantola, Phys. Earth Planet. Inter. 1998, 109, 1-8. [7] P. Vinet, J. Ferrante, J. H. Rose, J. R. Smith, J. Geophys. Res. 1987, 92, 9319-9325. [8] P. Vinet, J. H. Rose, J. Ferrante, J. R. Smith, J. Phys.: Condens. Matter 1989, 1, 1941-1963. [9] S. Seager, M. Kuchner, C. A. Hier-Majumder, B. Militzer, Astrophys. J. 2007, 669, 1279-
1297. [10] F. D. Stacey, Geophys. J. Int. 2000, 143, 621-628.
*E-mail: [email protected]
171
Crystallization and melting of minerals in-situ at high pressure
V.B. Prakapenka*1, I. Kantor1, A. Kantor2, P. Dera1, M.L. Rivers1, S.R. Sutton1 1CARS, University of Chicago, USA
2Bayerisches Geoinstitut, Germany
Detail knowledge of the fundamental processes of crystallization and melting of minerals at high pressures is one of the key factors in understanding the complexity of the Earth’s interior, its heterogeneous structure and dynamics. Pressure effects on the mechanism of crystal growth, melting phenomena and structure of the multi-component phases constituting the terrestrial and giant planets can be effectively studied with state-of-the-art technologies available at 3rd generation synchrotrons. In this work, we report the application of advanced, flat top laser heating technique combined with high resolution micro x-ray diffraction recently developed at GSECARS (APS, Argonne, USA) for in-situ high pressure/temperature studies of minerals in a diamond anvil cell (DAC)
[1]. We were able to
perform on-line melting experiments in the Mbar pressure range, one of the most challenging experiments in the DAC, unambiguously detecting melting by recording high quality diffuse x-ray scattering from molten materials at high pressures
[2]. The capability to maintain the
molten sample in the DAC for a relatively long time (at least 60 s) allowed us to collect high quality x-ray scattering data suitable for structure analysis of low-Z molten materials, such as Si, Ge, Fe and Fe compounds
[3]. According to our data, there are pre-melting phenomena that
result in considerable underestimation of melting temperatures measured in laser heated DAC using the speckle motion technique. Our observations of re-crystallization and melting phenomena existing at high pressure close to the melting temperatures are inconsistent with shear-induced, partially disordered viscous plastic flow which has been recently suggested
[4]
as an explanation for long standing disagreements between the results of static and shock-wave experiments, as well as theoretical calculations of melting curves for metals. The high quality experimental data (not limited to only transitional metals) were used as the basis for a conceptual model describing crystallization and melting processes at high pressures. This model will be presented and the implications of these results for understanding the composition and structure of the Earth's interior will be discussed.
[1] V. B. Prakapenka, A. Kubo, A. Kuznetsov, A. Laskin, O. Shkurikhin, P. Dera, M.L. Rivers, S.R. Sutton,. High Pressure Research. 2008, 28, 3225.
[2] G. Shen, V. B. Prakapenka, M. L. Rivers, S. R. Sutton, Phys. Rev. Lett. 2004, 92, 185701. [3] V.B. Prakapenka, Shen G.Y., Rivers M.L. et al, J. Syn. Rad., 2005, 12, 560. [4] J. C. Wu, P. Söderlind, J. N. Glosli and J. E. Klepeis, Nature Materials. 2009, 8, 223.
*Email : [email protected] Keywords: high pressure, melting, laser heating
172
Eutectic properties of primitive Earth’s magma ocean
D. Andrault1, G. Lo Nigro1, N. Bolfan-Casanova1, M. Mezouar2, J.-P. Perrillat2 1LMV, Université Blaise Pascal, 5 rue Kessler, 63000 Clermont-Ferrand, France
2ID27, European Synchrotron Radiation Facility, BP220, 38043 Grenoble, France
It is widely accepted that the early Earth was partially molten (if not completely) due to the high energy dissipated by terrestrial accretion [1]. After core formation, subsequent cooling of the magma ocean has led to fractional crystallization of the primitive mantle. The residual liquid corresponds to what is now called the fertile mantle or pyrolite.
Melting relations of silicates have been extensively investigated using the multi-anvil press, for pressures between 3 and 25 GPa [2,3]. Using the quench technique, it has been shown that the pressure affects significantly the solidus and liquidus curves, and most probably the composition of the eutectic liquid. At higher pressures, up to 65 GPa, melting studies were performed on pyrolite starting material using the laser-heated diamond anvil cell (LH-DAC) technique [4]. However, the quench technique is not ideal to define melting criteria, and furthermore these studies were limited in pressure range of investigation. Finally, the use of pyrolite may not be relevant to study the melting eutectic temperature. At the core-mantle boundary conditions, melting temperature is documented by a single data point on (Mg,Fe)2SiO4 olivine, provided by shock wave experiments at around 130-140 GPa [5]. These previous results present large uncertainties of ~1000 K.
The aim of this study is to determine the eutectic melting temperature in the chemically simplified system composed of the two major lower mantle phases, the MgSiO3 perovskite and MgO periclase. We investigated melting in-situ using the laser-heated diamond anvil cell coupled with angle dispersive X-ray diffraction at the ID27 beamline of the ESRF [6]. Melting relations were investigated in an extended P-T range comparable to those found in the Earth’s lower mantle, i.e. from 25 to 120 GPa and up to more than 5000 K.
Melting was evidenced from (a) disappearance of one of the two phases in the diffraction pattern, (b) drastic changes of the diffraction image itself, and/or (c) appearance of a broad band of diffuse X-ray scattering associated to the presence of silicate liquid. The pressure evolution of the eutectic temperature is found below the melting curve of pure MgSiO3 perovskite [7] for more than 500 K and also below the solidus curve of pyrolite [4] for 100-200 K at 60 GPa.
[1] B. T. Tonks, H. J. Melosh, Journal of Geophysical Research, 1993, 98, 5319. [2] K. Litasov, E. Ohtani. Physics of The Earth and Planetary Interiors, 2002, 134, 105. [3] E. Ito, A. Kubo, T. Katsura et al., Phys. Earth Planet. Inter., 2004, 143, 397. [4] A. Zerr, R. Boehler, Nature, 1994, 506. [5] J. A. Akins, S. N. Luo, P. D. Asimov et al., Geophys. Res. Lett., 2004, 31. [6] Schultz et al. International Journal of High Pressure Research., 2005, 25, 1, 71. [7] Zerr, A. and Boehler, R. Science, 1993, 262, 553.
*Email : [email protected] Keywords : DAC, YAG-laser, Diffraction, Earth
173
Ab initio molecular dynamics simulations of liquid fayalite (Fe2SiO4) at high pressures.
D. Muñoz Ramo*, L. Stixrude
Materials Simulation Laboratory & Department of Earth Sciences, University College London, London, United Kingdom
Fayalite (Fe2SiO4) is the iron-rich end member of (Mg,Fe)2SiO4 olivine. This is an important component of natural silicate liquids that has a major influence on the buoyancy of magma in Earth's interior, and thus on the chemical and thermal evolution of our planet. The extreme conditions at which silicate liquids may exist in the early and present-day Earth (136 GPa, 4000 K) are difficult to access experimentally. Computer simulations using ab initio methods are an alternative approach that can provide additional insight into the origin of physical behavior that has been applied to a number of liquid silicate systems[1,2], although not yet including Fe.
In this paper, we report ab initio molecular dynamics studies of liquid fayalite at high temperatures (6000K) and constant volume that allow us to predict different properties of the system. We use two different flavors of Density Functional Theory, GGA and GGA+U, to compare the performance of the two functionals. Previous studies in the solid phase have shown that GGA portraits fayalite as a metal, while the introduction of U leads to a correct description of the band gap and the magnetic ordering of the system. We extend this analysis to the liquid phase.
By means of these simulations we obtain structural data and thermodynamic properties of the liquid. We observe a trend to shorter distances between silicon and its neighboring ions, also observed in the case of iron, and longer distances between oxygen atoms and between iron atoms. The pressure, around 100-130 kbar, is in agreement with experimental estimates. Our calculations show large differences in the magnitude and orientation of the magnetic moments depending on the choice of functional; the GGA+U functional consistently provides larger values of the individual moments (about 1 unit larger) and of the total magnetization of the system.
[1] N. P. de Koker, L. Stixrude, B. B. Karki, Geochim Cosmochim Acta 2008, 72, 1427. [2] B. B. Karki, D. Bhattarai, L. Stixrude, Phys. Rev. B 2007, 76, 104205.
*Email : [email protected] Keywords: molecular dynamics, silicates
174
In situ viscosity measurements of liquid Fe-S alloys at high pressures
K. Funakoshi
Japan Synchrotron Radiation Institute, SPring-8, Sayo-cho, Hyogo, Japan
Knowledge of the viscosity of liquid Fe-S alloys at high pressures is an important for understanding the fundamental property and dynamics of the Earth’s outer core. Measurements of the viscosity of liquid Fe-S alloys have been attempted using the synchrotron radiation technique, however, previous experimental pressure ranges were insufficient to clarify the effect of pressure on the viscosity (< 7 GPa)
[1], [2]. Also in order to
estimate the reliable viscosity of the Earth’s outer core, the precise activation energy and activation volume are required, which are determined in a wide pressure range. In this study, we developed the viscosity measurements of liquid Fe-S alloys (Fe73S27, Fe80S20, Fe90S10)
combining with the x-ray radiography falling-sphere method and a multi-anvil press (SPEED-1500) at SPring-8.
An x-ray radiography technique with synchrotron radiation is very useful for the falling-sphere viscosity measurement, because it enables us in situ observation of the sinking process and determination of the reliable viscosity coefficient. Starting sample was a mixture of Fe and FeS powders, and a metal sphere (Re) marker was embedded in the upper part of the sample. High-speed and high-sensitive CCD camera provided a very good visual contrast between a metal sphere and the liquid. Real-time image of the sphere sinking was recorded in a very short exposure time (1/125 sec.). Terminal velocity of the sphere sinking was determined from the images, and the viscosity coefficient was calculated using the terminal velocity and a Stokes' law. We developed the various techniques and extended the pressure range to 14 GPa.
Viscosities of liquid Fe-S alloys decrease with increasing the temperature and the amount of sulfur content. These take a minimum value at close to 20 wt% sulfur content (eutectic composition). The pressure dependences of the viscosities are very small compared with the temperature dependences. The activation energies and the activation volumes were determined from the P-T dependences of the viscosities using a non-linear least square fitting. The activation energies of liquid Fe-S alloys increase linearly with the amount of iron content.
Viscosities of the Earth’s outer core were calculated using the activation energy and the activation volume of Fe90S10 between the inner core boundary and the core-mantle boundary. Our results are four orders of magnitude higher than the viscosities of pure iron
[3], [4]. These
results show that the addition of sulfur into the pure iron has a significantly large effect on the viscosity of the Earth’s outer core.
[1] H. Terasaki, T. Kato, S. Urakawa, K. Funakoshi, A. Suzuki, T. Okada, M. Maeda, J. Sato, J., T. Kubo, and S. Kasai, Earth Planet. Sci. Lett., 2001, 190, 93.
[2] M. D. Rutter, R. A. Secco, T. Uchida, L. Hongjian, Y. Wang, M. L. Rivers, and S. R. Sutton, Geophys. Res. Lett., 2002, 29(8), doi:10.1029/2001GL014392.
[3] J. P. Poirier, Geophys. J., 1998, 92, 99. [4] D. Alfe, G. Kresse, and M. J. Gillan, Phys. Rev., 2000, B61,132.
*E-mail : [email protected] Keywords: viscosity, liquid, Fe-S alloys, synchrotron
175
Physicochemical transformation of Al and SiO2 powders mixture under high pressure and modelling of the Earth’s interior
A.V. Dobromyslov*1, N.I. Taluts1, and E.A. Kozlov2 1Institute of Metal Physics, Ural Division of Russian Academy of Sciences,
Ekaterinburg, Russia 2Russian Federal Nuclear Center – Academician E. I. Zababakhin All-Russian Research
Institute of Technical Physics, Snezhinsk, Chelyabinsk region, Russia
The application of the spherical converging shock waves to a mixture of powders of different substances makes it possible to study the problems related to processes of synthesis and decomposition, caused by different chemical reactions occurring in solid and solid-liquid states, and the problems connected with the Earth’s interior. Experiment on modelling of the internal structure of the Earth have been lead by loading of a mixture of quartz and aluminium powders taken in a ratio 1:1 by spherical converging shock waves. The pressure on the external surface of the shell was 48 GPa. Calculation of the pressure realized in the converging shock wave and in the diverging shock wave has been made for the layers located at different distance from loading surface. After shock wave loading, a number of concentric layers are observed in a meridian section of the sample. The presence of several different zones in the sample reflects the specific features of physicochemical reactions occurring in the mixture of aluminium and quartz powders in different pressure ranges. It was established that at a pressures 22−25 GPa the grain size of quartz particles substantially decreases up to the transition to the X-ray amorphous state. As a pressure of ~45 GPa is reached, a solid-state reaction of SiO2 decomposition begins and leads to the precipitation of pure silicon and the of oxygen. The critical pressure, which is necessary for the Al2O3 formation, is about 50 GPa. Obtained data about phase state of transformation products into mixture of aluminium and quartz powders after shock wave loading are considered in respect to the structure of layers of the Earth mantle (Fig. 1). It was revealed, that the pressure of transition in amorphous state (~22−25 GPa) coincides with pressure of boundary between the upper and lower mantles.
This work was supported by the RFBR, project no. 08-05-00165.
*Email : [email protected] Keywords: pressure; shock waves; the Earth’s interior
Figure 1. Comparison of the data obtained about phase state of various layers of the sample after shock loading with position of layers in the Earth mantle.
176
High-pressure phase transitions in wüstite FexO
I. Kantor, V. Prakapenka
GeoSoilEnviroCARS, the University of Chicago,Chicago, IL, 60637, USA
FexO (mineral wüstite) is a strongly correlated oxide possessing interesting electronic properties (it is a prototypical Mott insulators) with a non-stoichiometric composition. FexO is also an important material for the Earth sciences as an end-member of (Mg,Fe)O ferropericlase, one of the most abundant minerals in the Earth lower mantle.
At ambient conditions FexO is cubic with the rock-salt structure, but the problem of the FeO ground state is still not resolved. It is known that at low temperatures non-stoichiometric FexO undergoes a distortional transition from a cubic (B1) structure to a trigonal (rhombohedral) rB1 phase[1]. A nearly stoichimetric FeO sample at liquid helium temperature was shown to be monoclinic with space group A2/m[2]. Theoretical ab initio calculations show[3] that there are at least two solutions for electronic orbital splitting at high pressures: with trigonal and monoclinic symmetry. At high pressures FexO also undergo B1->rB1 transition around 18 GPa. Recently it was shown by a single-crystal X-ray diffraction experiment[3] that about 80 GPa after laser heating FexO transforms to a monoclinic phase; however the experiment was limited to only one pressure point and was conducted under non-hydrostatic conditions.
We performed an X-ray diffraction study of two FexO single crystals (with x = 0.91 and 0.95) using diamond anvil cells and with Ne as a pressure medium, providing quasihydrostatic high-pressure conditions. The experiments were performed at the 13IDD beamline equipped with the heating laser at the Advanced Photone Source. Upon compression we observe a B1→rB1 transition, and the transition pressure strongly depend on the sample stoichiometry (around 17 GPa for the Fe0.95O and around 21 GPa for the
Fe0.91O). The transition was found to be a week first-order transition, because two phases coexist in a few GPa pressure range. After laser heating at pressure around 40 GPa both samples transform to a monoclinic mB1 phase. At high temperatures we observe reversible transitions mB1-rB1-B1 during heating and B1- rB1-mB1 during cooling. This implies that the monoclinic phase is stable at room temperatures and is not stabilized by a non-hydrostaticity. The figure shows pressure evolution of the cubic (220) reflection d-spacing of the Fe0.91O sample upon compression. It remains a single peak up to 21 GPa (B1 phase, green line). In rhombohedral rB1 phase it splits into two peaks (red lines) and further into five peaks (blue lines) in monoclinic mB1 phase. Red arrows show pressures of laser heating. Note that at 60 GPa laser annealing releases non-uniform strains and peaks position slightly change.
[1] N. C. Tombs, H. P. Rooksby, Nature 1950, 165, 442. [2] H. Fjellvåg, B. C. Hauback, T. Vogt, S. Stølen, Am. Miner. 2002, 87, 347. [3] S. A. Gramsch, R. E. Cohen, S. Y. Savrasov, Am. Miner. 2003, 88, 257. [4] I. Kantor, A. Kurnosov, C. McCammon, L. Dubrovinsky, Z. Kristallogr. 2008, 223, 461.
*Email : [email protected]
177
Detection of the spinel–post-spinel transition in Fe3O4 by in situ electrical resistivity measurements at high pressures and temperatures
K. Schollenbruch1, A.B. Woodland*1, D. Frost2, F. Langenhorst2 1Goethe Universität, Inst. für Geowissenschaften, Frankfurt am Main, Germany
2Bayerisches Geoinstitut, Bayreuth, Germany
Spinel-structured phases are of geological and material scientific importance. Many of these, including magnetite (Fe3O4), are known to transform to a "post-spinel" phase at high P and T. Understanding the behavior of the Fe3O4 polymorphs is of fundamental importance for the model Fe-O system. However, the post-spinel phase (h-Fe3O4) unquenchable, requiring in situ measurements to constrain the phase boundary and study the properties of this high-P phase. Considering the differences in resistivity apparently observed for magnetite and h-Fe3O4 at room T and elevated P[1,2], in situ measurement of electrical resistivity should provide a means for tracking the phase boundary between these two phases at high P and T. Experiments were performed in a 5000 ton multi anvil press and used standard pressure cells except that two WRe thermocouples were positioned on each side of a hot-pressed cylinder of magnetite (1.x1.5mm). The thermocouple leads served as four-electrodes, allowing resistance to be measured with an applied external DC current (40 mA). Additional measurements without an applied current allowed us to isolate the signal originating from the Fe3O4 sample. After pressurizing the sample to the target pressure, sample resistance was measured as a function of temperature; during both heating and cooling.
Measurements at 8 and 9 GPa were reproducible during heating (up to 1400°C) and cooling, indicating the stability of magnetite under these conditions. A local resistivity maximum at 500-600 °C could be related to the paramagnetic-ferrimagnetic transition in magnetite[3]. This same behavior also occurred during heating at 10 and 12 GPa, however, a jump in resistivity was observed at ~900-1300°C and upon cooling (also with subsequent reheating), different ρ-T systematics are observed. This change is interpreted as indicating the magnetite–h-Fe3O4 transition. Here h-Fe3O4 behaves like a semiconductor rather than a metal[2].
In the recovered samples from 10 and 12 GPa, extensive twin lamellae and other defect structures are present in the magnetite, which are absent in the samples run at ~9 GPa. These structures provide evidence for the back-reaction of h-Fe3O4 to magnetite during decompression after the experiment and support our interpretation of the resistivity data. Although the T at which h-Fe3O4 first appears is no doubt kinetically controlled, the observed stability of magnetite up to 1400°C at 9 GPa and appearance of h-Fe3O4 at 10 GPa places important constraints on the position of the phase boundary, implying a very flat dP/dT. This study demonstrates the utility of in situ resistivity measurements at high P and T for determining phase boundaries between phases with moderate electrical conductivities.
[1] E.R. Morris, Q. Williams, J. Geophys. Res. 1997,102, 18139-18148. [2] L. S. Dubrovinsky, N. A. Dubrovinskaia, C. McCammon, G. Kh. Rozenberg, R. Ahuja, J. M.
Osorio-Guillen, V. Dmitriev, H. P. Weber, T. Le Bihan, B. Johansson, J. Phys.: Condensed Matter. 2003, 15, 7697-7706.
[3] R. Parker, C.J. Tinsley, Phys. Stat. Sol. 1976, 33, 189-194.
*Email : [email protected] Keywords: magnetite, resistivity, phase transformation, post-spinel
178
High pressure electronic transition in hcp Fe and Fe0.9Ni0.1
K. Glazyrin*1, O. Narygina1, C. McCammon1, L. Dubrovinsky1, B. Hewener2, V. Schünemann2, J. Wolny2, K. Muffler2, A. Chumakov3
1Bayerisches Geoinstitut, Bayreuth, Germany 2Technical University Kaiserlautern, Kaiserlautern, Germany
3ESRF, Grenoble, France
We performed high pressure Mössbauer experiments on Fe0.9Ni0.1 and on pure iron as well as nuclear resonant inelastic x-ray scattering (NIS) experiments on Fe0.9Ni0.1. The studied materials were loaded in diamond anvil cells (DAC) with quasi hydrostatic pressure medium.
The experiments were conducted at room temperatures.
The NIS data on iron-nickel alloy shows anomalous deviation from Birch’s law for mean sound velocity at 42 GPa. Previous experiments[1,2] conducted on same or similar materials also demonstrate a deviation from Birch's law.
The Mössbauer experiments revealed anomalous behavior of central shifts for both materials at pressures ~40 GPa (Figure 1). The change of central shift in absence of magnetic transition (the calculated afm-II to nonmagnetic state transition is ~60 GPa [3] at T=0K) is the evidence of previously unknown electronic transition in iron.
(a) (b) Figure 1 Central shift in pure Fe and FeNi alloy
[1] Jung-Fu Lin, V.V. Struzhkin, W. Sturhahn, E. Huang, J. Zhao, M.Y. Hu, E.E. Alp, H.-K. Mao, N. Boctor, R.J. Hemley, Geophys. Res. Lett., 2003, 30, 11/1-4
[2] H. K. Mao, J. Xu, V.V. Struzhkin, J. Shu, R. J. Hemley, W. Sturhahn, M. Y. Hu, E. E. Alp, L. Vocadlo, D. Alfè, G. D. Price, M. J. Gillan, M. Schwoerer-Böhning, D. Häusermann, P. Eng, G. Shen, H. Giefers, R. Lübbers, G. Wortmann, Science, 2001, 292, 914-916
[3] G. Steinle-Neunmann, L. Sixtrude, R.E. Cohen, Phys. Rev. B, 1999, 60, 791-799
*Email : [email protected] Keywords : hcp-iron high-pressure transition
179
Molecular dynamics simulations of oil components at geological conditions
J. Ho, S. Reimer, N. Weinberg*
Department of Chemistry, University of the Fraser Valley, Abbotsford, Canada
Modern methods of computational chemistry, including molecular dynamics and quantum mechanics of molecular systems, allow one to obtain accurate values of structural parameters and physicochemical properties of complex systems for a wide range of temperatures and pressures without resorting to experiment. In this work we explore the effects of physical conditions on densities and viscosities of typical petroleum components, including hexane, octane, dodecane, and octadecane, for temperatures and pressures ranging from ambient conditions (298 K, 1 bar) to geophysical conditions of the upper mantle (2000 K, 60 kbar). Theoretical results are compared to the experimental data and show good agreement in case of densities and somewhat poorer agreement for viscosities (diffusion coefficients).
*Email : [email protected] Keywords: hydrocarbons, viscosity, density, molecular dynamics
180
Single crystal structural refinement of high and low spin siderite up to 54 GPa
B. Lavina*1, P. Dera2, R. T. Downs3, O. Tschauner1, W. Yang4, G. Shen4, M. Nicol1 1HiPSEC, University of Nevada, Las Vegas, USA
2GSECARS, University of Chicago, Argonne, USA 3University of Arizona, Tucson, USA
4HPCAT, Carnegie Institution of Washington, Argonne, USA
The accurate determination of the high pressure properties of siderite is important in the study of the Earth’s interior given the controversial stability of carbonates in the deep Earth, their relevance for the deep carbon cycle, and the great influence on the mantle properties and dynamics of the carbon phases. The properties of siderite, the iron member of the calcite series, are severely affected by the iron spin transition which was first observed by XES[1], then further investigated by X-ray diffraction [2] and ab initio calculations [3]. Single crystal diffraction data on a specimen of natural siderite from Ivigtut (Greenland) were collected at Station 16BMD, APS, ANL in the range 0-54 GPa. Structural refinements of about 40 independent reflections in the range 1.7-0.8 Å converged to R1 from 3 to 5 % and constrained well these four parameters: the scale factor, the oxygen positional parameter and the isotropic displacement parameters of Fe and O. The general trends in the high pressure behavior of rhombohedral carbonates, where rigid CO3 units alternate with octahedra undergoing the largest deformations, is confirmed for siderite in the whole pressure range. However, beyond this trend we can distinguish fine variations of octahedral distortion associated with the spin transition. Fe-Fe interactions [3] may appreciably influence the geometry of the structure.
Support from DOE, NSF and NNSA are gratefully acknowledged.
[1] A. Mattila, T. Pylkkanen, J.P. Rueff, S. Huotari, G. Vanko, M. Hanfland, M. Lehtinen., K. Hamalainen, Journal of Physics-Condensed Matter (2007) 19.
[2] B. Lavina, P. Dera, R.T. Downs, V. Prakapenka, AGU Fall Meeting (2008) abstract # MR31A-1835.
[3] H. Shi, W. Luo, B. Johansson, R. Ahuja, Physical Review B (2008) 78.
*Email : [email protected] Keywords: siderite, single-crystal, spin transition
181
A-cation effect on the compressibility of ACoF3 perovskites
F. Aguado*1,2, F. Rodríguez1, S.A.T. Redfern2 1MALTA-Consolider Team, DCITIMAC, Universidad de Cantabria, Santander, Spain,
2Department of Earth Sciences, University of Cambridge, Cambridge, UK
Perovskite is one of the most commonly studied structure due to the variety of physical properties and phenomena in material science and geophysics. The high pressure behaviour has been intensely explored in some oxides regarding transformations to postperovskite phases and decomposition into simple oxides. However halide perovskites, in spite of being good analogs of higher compressibility,
[1] have not been so intensively investigated. The roll of
A cations on the crystal compressibility can shed light on the mechanism governing the high pressure evolution of oxides. The aim is to study the structure evolution of ACoF3 perovskites with pressure. Attention is paid on their distortion propensity.
KCoF3 and RbCoF3 have the perovskite structure at ambient conditions, their tolerance factor being 1.01 and 1.04, respectively. On the other hand, CsCoF3 adopts a 9L or 6L structure depending on the synthesis conditions,
[2]
whereas the smallest cation in the series (Na) provides a distorted perovskite structure (Pbnm),
[3] with a tolerance factor of 0.93. The
evolution of KCoF3 and RbCoF3 has been explored by angle-dispersive x-ray diffraction under high hydrostatic pressure conditions. In both compounds the perovskite structure remains undistorted in the 0-20 GPa range (Fig.1). This result together with previous structural data on isostructural ABF3 compounds, e.g. KMgF3,
[1] confirm the stability
to compression of cubic perovskites with tolerance factors greater than 1. However, the bulk moduli are quite different due to steric effects at the A site. Consequently, substantial differences can be found in the compressibility of the AF12 and BF6 forming polyhedra. In this way, the equation-of-state (EOS) of KF12 has been obtained from KMgF3 and KCoF3 while EOS of CoF6 from KCoF3 and RbCoF3. We compare the polyhedron and crystal compressibilities of several compounds in order to establish structural correlations.
[1] F. Aguado, F. Rodriguez, S. Hirai, J. N. Walsh, A. Lennie, S. A. T. Redfern, High. Pressure Res. 2008, 28, 539.
[1] J. M. Longo, J. A. Kafalas, J. Solid State Chem. 1969, 1, 103. [2] B. Luetgert, D. Babel, Z. Anorg. Allg. Chem. 1992, 616, 133.
*Email : [email protected] Keywords: Perovskite, ABF3, compressibility, equation-of-state
6 8 10 12 14 16 18 20
Inte
sity
(ar
b.u
n.)
2 (deg.)
0.3 GPa
3 GPa
7.7 GPa
13.3 GPa
19.1 GPa
= 0.4153 Å
Fig.1 XRD pattern of RbCoF3 under pressure. The cubic structure remains stable up to 20 GPa, as in KCoF3 and KMgF3.
182
High-pressure ferroelastic transition in K0.8Na0.2AlSi3O8 hollandite
T. Boffa Ballaran*1, J. Liu1, L. S. Dubrovinsky1, R. Caracas2, W. Crichton3 1Bayerisches Geoinstitut, Universitaet Bayreuth, Bayreuth, Germany
2Centre National de la Recherche Scientifique, Laboratoire de Sciences de la Terre, UMR5570, Ecole Normale Supérieure de Lyon, Lyon, France
3European Synchrotron Radiation Facility, BP 220, Grenoble, France
We used X-ray synchrotron powder diffraction, Raman spectroscopy and first-principles calculations to characterize the high-pressure ferroelastic tetragonal I4/m to monoclinic I2/m transition of K0.8Na0.2AlSi3O8 hollandite. The transition displays classical second-order character with an equilibrium transition pressure of 17 GPa renormalized by coupling of the soft optic mode with the spontaneous strain. Strain coefficients have been calculated by extrapolating the tetragonal lattice parameters into the monoclinic stability field using a linearised second-order Birch-Murnaghan equation of state. The bare elastic constant of the tetragonal hollandite have been obtained using first principles calculations in the framework gradient generalized approximation of the density-functional theory in the ABINIT implementation[1]. The K-Na solid solution is treated in the virtual crystal approximation[2]
constructing alchemical pseudopotentials for the [K0.8Na0.2] atom[3]. This approach proved to yield highly accurate elastic constants and vibrational properties for solid solutions[4]. The variations of the lattice strains and of the frequency of the soft optic mode with pressure as well as a linear pressure dependence of the bare elastic constant calculated for the tetragonal phase have been used to develop a Landau free energy expansion to describe the elastic constant variations of K0.8Na0.2AlSi3O8 across the transition.
[1] X. Gonze, G. M. Rignanese, M. Verstraete, J. M. Beuken, Y. Pouillon, R. Caracas, F. Jollet, M. Torrent, G. Zerah, M. Mikami, P. Ghosez, M. Veithen, V. Olevano, L. Reining, R. Godby, G. Onida, D. Hamann, D. C. Allan, Z. Kristallog. 2005, 220, 558.
[2] L. Bellaiche, D. Vanderbilt, Phys. Rev. B 2000, 61, 7877-7882. [3] M. Giantomassi, L. Boeri, G. B. Bachelet, Phys. Rev. B 2005, 72, 224512. [4] R. Caracas, E. J. Banigan, Phys. Earth Planet. Inter. 2009, doi:10.1016/j.pepi.2009.01.001
*Email : [email protected] Keywords : High-pressure phase transition, Landau free energy, Spontaneous strain, Elastic constants.
183
Pressure effect on upper-mantle rheology: Insights from single-crystal experimental deformation at mantle P and T
P. Raterron1*, E. Amiguet1, P. Cordier1, J. Chen2, J. Girard2,T. Geenen3 1LSPES (CNRS 8008), Université Lille 1, Villeneuve d’Ascq, France
2The CeSMEC, Florida International University, Miami, USA 3Department of Theoretical Geophysics, Faculty of Geosciences, Utrecht, The Netherlands
Recent developments in high-pressure deformation devices coupled with synchrotron radiation allow investigating the rheology of mantle minerals at the extreme pressure (P) and temperature (T) of their natural occurrence. During deformation, the differential stress (t) applied on specimens and the resulting specimen strain (ε) and strain rate (dε/dt) are quantified in situ by time-resolved X-ray diffraction and radiography. We present here the investigation, using these new techniques, of the effect of P on the rheology of two important upper-mantle minerals: olivine, its main constituent, and diopside, a good representative of mantle clinopyroxenes (cpx) which are major constituents of eclogites.
Steady state deformation experiments were carried out in poor water conditions at P up to 9 GPa and T up to 1400°C on pure forsterite (Fo100) and San Carlos olivine (Fo89) crystals, and on diopside crystals, using the Deformation-DIA apparatus (D-DIA)[1] that equipped the X17B2 beamline of the NSLS (Upton, NY, USA). Single crystals were oriented in order to activate dislocation slip systems characteristic of olivine and diopside high-T deformation: in olivine, either the [100] or [001] slip in (010) plane, or both [100](001) and [001](100) slip systems together; in diopside the duplex ½<110>{1 -1 0} systems, or both [100](010) and [010](100) systems together, or again [001] slip in (100), (010) and {110} planes. For each mineral, experiments were designed either to compare the activity of different slip systems, or to quantify the effect of P on crystal plasticity - i.e., the activation volume V* in classical power creep laws - by comparing the obtained high-P deformation data with similar data obtained at room P on similar crystals[2-4]. Run product microstructures were investigated by transmission electron microscopy (TEM).
In olivine, a slip transition with increasing P, from dominant [100] slip to dominant [001] slip, is documented[5] and may have significant implications for upper mantle lattice preferred orientations (LPO) and low viscosity zone. In diopside, we show that ½<110> slip and [001] slip dominate deformation and have comparable activities at mantle P and T. This latter observation allows interpreting the LPO observed in naturally deformed eclogites.
[1] Y. Wang, W.B. Durham, I.C. Getting, D.J., Weidner, Rev. Sci. Instr., 2003, 74, 3002. [2] M. Darot, Y. Gueguen, J. Geophys. Res., 1981, 86, 6219. [3] Q. Bai, S.L. Mackwell, D.L. Kohlstedt, J. Geophys. Res., 1991, 96, 2441. [4] P. Raterron, O. Jaoul , J. Geophys. Res., 1991, 96, 14277. [5] P. Raterron, E. Amiguet, J. Chen, L. Li, P. Cordier, Phys. Earth Planet. Int., 2009, 172, 74.
*Email : [email protected] Keywords: olivine, diopside, deformation, extreme conditions
184
Use of the spark plasma sintering (SPS) technique in the preparation of geological samples suitable for high-pressure experiments
M. Bystricky, F. Béjina*, J. Ingrin
Laboratoire des Mécanismes et Transferts en Géologie, Observatoire Midi-Pyrénées, Université de Toulouse III, 14 av. Édouard Belin, 31400 Toulouse, France
SPS is a recent technique for sintering dense polycrystalline aggregates in very short times (minutes). The process itself is comparable to conventional hot-pressing but allows very rapid heating and cooling of the sample. The so-obtained pellets can be of various sizes, typically of the order of centimetric. We used this technique to sinter a series of specimens, forsterite, MgO, enstatite, etc. and we propose to show how this technique is perfectly suitable for preparing geological samples for high-pressure experiments. In addition to presenting the physical characteristics of these samples (density, micro-structure...), we will also show a few experiments we performed with such aggregates at high pressure, i.e. deformation of mantle minerals at 5 GPa and high temperature, phase transformation to transition zone minerals, etc.
*Email : [email protected] Keywords: sintering, polycrystalline aggregates, mantle minerals, silicates
185
Sound attenuation and dispersion in vitreous silica
S. Ayrinhac1, M. Foret*1, B. Rufflé1, R. Vacher1, A. Polian2 1Université de Montpellier 2, Laboratoire des Colloïdes, Verres et Nanomatériaux,
UMR 5587 CNRS, F-34095 Montpellier Cedex 5, France 2Université Pierre et Marie CURIE, Institut de Minéralogie et de Physique des Milieux
Condensés, 4 place Jussieu, case postale 115, F-75252 Paris Cedex 5, France
Recent progress has been achieved in the understanding of the frequency and temperature dependencies of sound attenuation and dispersion in vitreous silica[1-3]. Above liquid helium temperature (T) and up to the hypersonic frequency range, sound damping is controlled mainly by two processes which are in order of the frequency at which they dominate: the thermal relaxation of defects and the anharmonic interactions with the thermal bath also called “network viscosity”. We found that in the Brillouin frequency range, at 35 GHz and room T, the contribution of anhamonicity to internal friction is about twice that of thermally activated relaxations. The ratio increases with T and frequency. The analysis allows determining the expected contributions to velocity dispersion. We find a strong increase of
the bare velocity v with T indicating that silica experiences a progressive structural change with increasing T. Some simulations attribute this anomalous hardening to a progressive local polyamorphic transition associated with abrupt rotations of Si-O-Si bonds[4]. Furthermore, we report on new accurate Brillouin data in v-SiO2 under hydrostatic pressure at room T in the range 0 – 6 GPa. In this pressure range, no irreversible changes are observed, neither in velocity nor in absorption. As already well-reported, the pressure dependence of the velocity shows a pronounced minimum slightly above 2 GPa. Most interesting, the absorption exhibits a dramatic rise under pressure and passes through a maximum nearly at the same pressure value, ~ 2 GPa. The results are analyzed on the basis of the pressure dependence of the relaxing defects.
[1] R. Vacher, E. Courtens, M. Foret, Phys. Rev. B 2005, 72, 214205. [2] E. Courtens, M. Foret, R. Vacher, B. Rufflé, Phys. Chem. Glasses: Eur. J. Glass Sci. Technol. B 2007, 48, 9-18. [3] A. Devos, M. Foret, S. Ayrinhac, P. Emery, B. Rufflé, Phys. Rev. B 2008, 77, 100201R. [4] L. Huang and J. Kieffer, Phys. Rev. B 2004, 69, 224203.
*Email : [email protected] Keywords: Glasses, acoustic properties, Brillouin scattering
186
5-coordinated silicon in Earth’s mantle materials
L. Gautron*1, T. Tsuchiya2, S. Gréaux2, I. Daniel 3, D. Andrault4, J. Tsuchiya2, J. Dubrail1
1. Laboratoire Géomatériaux et Géologie de l’Ingénieur, Université Paris-Est Marne la Vallée, Champs-sur-Marne, Marne la Vallée, France
2. Geodynamics Research Center, Ehime University, Matsuyama, Japan 3. Laboratoire Sciences de la Terre, Ecole Normale Supérieure, Lyon, France
4. Laboratoire Magmas et Volcans, Université Blaise Pascal, Clermont-Ferrand, France
Earth silicate minerals are usually built with silicon atoms coordinated by 4 and 6 oxygen atoms at low and high pressures respectively. Then SiO4 tetrahedra and SiO6 octahedra have long been assumed to be the fundamental building units of minerals relevant to the mineralogy of the Earth’s interior.
Nevertheless, theoretical and experimental studies proposed the presence of pentacoordinate silicon in silicate melts and glasses brought to high pressure and high temperature
[1]. Also few theoretical studies showed the possible existence of five-coordinated
silicon in high-pressure mineral phases: a distorted square pyramid or a trigonal bipyramid in SiO2 quartz under non-hydrostatic stress
[2] and in Al2SiO5 meta-sillimanite
[3]; a square-based
pyramid in MgSiO3 enstatite[4]
. The first structural characterization of five-coordinated silicon in a high-pressure crystalline phase was obtained for CaSi2O5
[5]. In this triclinic titanite-like
phase, the SiO5 polyhedra were formed by removing one oxygen atom from SiO6 octahedra, naturally producing a square-based pyramid.
Based upon theoretical data obtained from ab initio calculations and experimental data obtained from high-pressure X-Ray Diffraction (HP-XRD), we propose that the CAS phase of composition CaAl4Si2O11
[6] is the second high pressure crystalline phase which could display
SiO5 units. Both static enthalpy calculations and Rietveld analysis of XRD data evidence a transition from the room-pressure structure to a high-pressure structure characterized by pentacoordinate silicon located in a trigonal bipyramid. Such transition would require a compositional change in the M1 layers.
The intermediate coordination 5 for silicon is expected to strongly influence the transport properties of silicate mantle materials, and to play a central role in many dynamic processes occurring in silicates. After the theoretical results mentioned above and the experimental data obtained on the CAS phase, the importance of 5-coordinated silicon in mantle materials is discussed.
[1] X. Xue, J.F. Stebbins, M.Kanzaki, P.F. McMillan, B. Poe, 1991, Am. Mineral. 1991,76, 8. [2] J. Badro, D.M. Teter, R.T. Downs, P. Gillet, R. Hemley, J-L. Barrat, Phys. Rev., 1997, B 56,
5797. [3] A.R. Oganov, G.D. Price, J.P. Brodholt, Acta Crystallogr. 2001, A57, 548. [4] S.L. Chaplot, N. Choudhury, Solid State Comm. 2000, 116, 599. [5] R.J. Angel, N.L. Ross, F. Seifert, T.F. Fliervoet, Nature 1996, 384, 441. [6] L. Gautron, S.E. Kesson, W.O. Hibberson, Phys. Earth Planet. Int. 1996, 97, 71.
*Email : [email protected] Keywords: pentacoordinate silicon, high-pressure, mantle, dynamic processes.
187
Molecular Systems
Lectures Ab-initio simulation of simple molecular systems at extreme conditions ___________ 189
Structure of molecular CO2 at high pressures and temperatures __________________ 190
High pressure formation and characterization of a previously unobserved
structure of clathrate hydrate _______________________________________ 191
Salty ice VII under pressure ________________________________________________ 192
Posters MS 01 : Ultrasonic study of epsomite (MgSO4·7H2O) under pressure _______________ 193
MS 02 : Pressure–induced Raman spectral changes in [DEME][BF4] ________________ 194
MS 03 : Pressure-induced phase transition of ice in aqueous KOH solution __________ 195
MS 04 : Structural transformation and dynamical properties of barium peroxide
at high pressure __________________________________________________ 196
MS 05 : Water-Methane Mixtures at Extreme Conditions ________________________ 197
MS 06 : The structure of methane, phase A ___________________________________ 198
MS 07 : High-pressure studies of ammonia hydrates ____________________________ 199
MS 08 : The relationship between Ice VII and Ice VIII ____________________________ 200
MS 09 : Sound velocity of an equimolar N2/CO2 mixture at high pressure and
high temperature _________________________________________________ 201
MS 10 : Size-driven phase diagram in TGS crystals under high hydrostatic
pressure. ________________________________________________________ 202
MS 11 : Influence of the high hydrostatic pressure on the ferro–paraelectric
phase transition in TGS crystal. ______________________________________ 203
188
189
Ab-initio simulation of simple molecular systems at extreme conditions
S. Scandolo*
The Abdus Salam International Centre for Theoretical Physics, and CNR-INFM Democritos National Simulation Center, Trieste, Italy
Water, methane, and carbon dioxide are among the most stable molecules at ambient conditions, but under extreme conditions of pressure and temperature they undergo dramatic chemical changes including dissociation, ionization, and polymerization. Understanding such changes has far ranging implications in planetary sciences, chemistry, biophysics, and geochemistry. Molecular CO2 has been reported to collapse into extended covalently bonded polymeric polymorphs when compressed to pressures above 45-50 GPa [1]. Seeming similarities with compressed silica are disproved by ab-initio simulations, which yield for the crystalline phases evidence for the stability of tetrahedral CO4 units in a wide pressure range [2,3], and a mixture of three- and four-fold carbon coordination for the amorphous form [4]. H2O and CH4 are the main constituents of the ``ice" middle layer of Neptune and Uranus, where they form a fluid mixture that undergoes progressive ionization as a function of increasing pressure and temperature along the planetary radius [5]. We have simulated by ab-initio molecular dynamics a CH4/H2O mixture at PT conditions representative of undissociated, partially dissociated, and fully dissociated regimes for water [6]. We find that changes in the water structure have dramatic consequences on the solvation, ionization, and full dissociation of methane [7].
[1] V. Iota, C. S. Yoo, and H. Cynn, Science 1999, 283, 1510; S. Serra, C. Cavazzoni, G. L. Chiarotti, S. Scandolo, and E. Tosatti, Science 1999, 284 , 788; M. Santoro, F.A. Gorelli, R. Bini, G. Ruocco, S. Scandolo, and W.A. Crichton, Nature 2006, 441, 857
[2] M.-S. Lee, J.A. Montoya, and S. Scandolo, Phys. Rev. B 2009, 79, 144102 [3] J. Sun, D.D. Klug, R. Martonak, J.A. Montoya, M.-S. Lee, S. Scandolo, E. Tosatti, Proc. Natl.
Acad. Sci. USA 2009, 106, 6077 [4] J.A. Montoya, R. Rousseau, M. Santoro, F. Gorelli, and S. Scandolo, Phys. Rev. Lett. 2008,
100, 163002 [5] W.J. Nellis, N.C. Holmes, A.C. Mitchell, D.C. Hamilton, M. Nicol, J. Chem. Phys. 1997, 107,
9096 [6] C. Cavazzoni, G.L. Chiarotti, S. Scandolo, E. Tosatti, M. Bernasconi, M. Parrinello, Science
1999, 283, 44 [7] M.-S. Lee and S. Scandolo, to be published
*E-mail : [email protected]
Keywords : Ab-initio simulations, Planetary science, Carbon dioxide, Water, Methane
190
Fig. 1: Phase diagram of CO2 at high P-T. Different colours distinguish molecular from non-molecular phases. The dashed lines show extrapolations of measurements, the dash-dotted line is thought to be a kinetic line and dotted lines are hypothetic transition lines reproduced from Ref. 5.
Structure of molecular CO2 at high pressures and temperatures
F. Datchi1,*, V. M. Giordano2, A.M. Saitta1, and P. Munsch1
1 Physique des Milieux Denses, IMPMC, CNRS UMR 7590, Université Pierre et Marie Curie-Paris VI, 140 rue de Lourmel, 75015 Paris, France
2ESRF, 6 rue Jules Horowitz, BP220, 38043 Grenoble CEDEX, France
Several new polymorphs of carbon dioxide have been discovered in the last decade, presenting either a molecular (phases II, IV and VII) or non-molecular (phases V, VI and amorphous) character. The resulting phase diagram as presently known is shown in Fig. 1. Knowledge of the structure of these phases is crucial in order to understand their bonding properties and the microscopic mechanisms that underlie the transformation from the molecular to non-molecular forms. There are at present large debates regarding the structure of several of these phases. We will mostly focus here on phase IV which is the molecular phase stable at the highest P-T conditions prior to the formation of non-molecular phase V. Phase IV was proposed to be an ‘intermediate bonding state’ between molecular phase I and extended phase V, based on the finding that the molecules are strongly bent (160°) and elongated (1.5334 Å compared to 1.1618 Å in phase I) in the Pbcn structure matching the experimental powder pattern [1]. This structure has been contested by several studies [2,3,4], urging the need for a new experimental investigation.
We have succeeded in growing single crystals of phase IV in a DAC and determined its structure using x-ray diffraction. The latter has no resemblance with that previously published [1] and provides the definite proof that CO2 remains a purely
molecular solid in these P-T conditions. These experimental results will be discussed together with new ab-initio calculations that confirm the stability of the structure and provide additional insight into the thermodymanic stability range of all molecular phases.
[1] J. H. Park, C. S. Yoo, V. Iota, H. Cynn, M. F. Nicol, and T. Le Bihan, Phys. Rev. B 68, 014107 (2003).
[2] S. A. Bonev, F. Gygi, T. Ogitsu, and G. Galli, Phys. Rev. Lett. 91, 065501 (2003). [3] F. A. Gorelli, V. M. Giordano, P. R. Salvi, and R. Bini, Phys. Rev. Lett. 93, 205503 (2004). [4] V. M. Giordano and F. Datchi, Eur. Phys. Lett. 77, 46002 (2007). [5] V. Iota, C. S. Yoo, J. H. . Klepheis, Z. Jenei, W. Evans, and H. Cynn, Nature Mat. 6, 34 (2006).
*E-mail : [email protected]
Keywords: Molecular crystal, structure, bonding
1600
1400
1200
1000
800
600
400
T(K
)
706050403020100
P (GPa)
I
IVVII
Fluid
III
II
Amorphous
VI
V
191
High pressure formation and characterization of a previously unobserved structure of clathrate hydrate
C.A. Tulk 1, L. Yang 1,2, D.D. Klug3, I.L. Moudrakovski3, C.I. Ratcliffe3, J.A. Ripmeester3, B.C. Chakoumakos1, L. Ehm4, C.D. Martin5, and J.B. Parise 4
1Neutron Scattering Science Division, Oak Ridge National Laboratory 2Center of Nanophase Materials Science, Oak Ridge National Laboratory
3Steacie Institute for Molecular Sciences, National Research Council of Canada 4Mineral Physics Institute, Department of Geosciences, Stony-Brook University
5X-ray Sciences Division, Advanced Photon Source, Argonne National Laboratory
Clathrate hydrates (or gas hydrates) are a class of water inclusion compounds formed when water molecules hydrogen bond to form a crystalline lattice of cages that are stabilized by guest atoms or molecules. Generally, the structure of clathrate hydrates fall into three categories, two cubic forms known as sI and sII and a hexagonal form known as sH. At low pressures small guest atoms and molecules such as noble gasses and methane, nitrogen, oxygen, and carbon dioxide form the cubic form while larger molecules such as cyclooctane form sH in the presence of a small help gas molecule. Recently, small molecules such as methane have been shown to form the sH form at elevated pressure, in those forms small clusters of guests play the role of large molecules at low pressure and stabilize the large cage. We have recently synthesized and characterized a new structure of gas hydrate[1]. This structure is formed by a pressure quench recovery technique starting with the cubic sI xenon clathrate hydrate. The structure was found to be related to the high pressure hexagonal form but with distinct differences, particularly regarding cage structure, occupancy and hydration number of guest-to-host. This structure was found to show remarkable meta-stability at ambient pressure before reverting to the starting sI material. This system has been reproducibly synthesized three times and high energy x-ray diffraction, powder x-ray diffraction, nuclear magnetic resonance magic angle spinning, inelastic neutron scattering and molecular dynamics simulation data have been collected and used in the analysis.
[1] L. Yang, C. A. Tulk, D. D. Klug, I. L. Moudrakovski, C. I. Ratcliffe, J. A. Ripmeester, B. C. Chakoumakos, L. Ehm, C. D. Martin, and J. B. Parise, PNAS, 106 (2009).
* E-mail : [email protected]
Ice, Water, Clathrate Hydrate
192
Salty ice VII under pressure
L.E. Bove1, S. Klotz1, Th. Strässle2, T.C. Hansen3, A.M. Saitta1 1Physique des Milieux Denses, IMPMC, CNRS-UMR 7590,
Université P&M Curie, 75252 Paris, France 2Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institut,
Villigen, Switzerland 3Institut Laue Langevin, BP 156, F-38042 Grenoble, France
It is widely accepted that ice, no matter what phase, is unable to incorporate large amount of salt into its structure. This conclusion is based on the observation that upon freezing of salt water, ice expels the salt almost entirely into brine, a fact which can be exploited to desalinate seawater. Here we show, by neutron diffraction measurements under high pressure, that this behavior is not an intrinsic physico-chemical property of ice phases. We demonstrate that substantial amounts of dissolved LiCl can be built homogeneously into the ice VII structure if it is produced by re-crystallization of its glassy state under pressure [1]. Such ‘ alloyed‘ ice VII has significantly different structural properties compared to pure ice VII, such as a 8% larger unit cell volume, 5 times larger displacement factors, an absence of a transition to an ordered ice VIII structure, plasticity, and most likely ionic conductivity.
[1] S. Klotz, L.E. Bove, T. Strassle, T. Hansen, and M. Saitta, Nature Materials 2009, 8, 405.
*Email : [email protected] Keywords : Ice, neutron diffraction, structure
Figure 1. Neutron diffraction pattern of LiCl×6D2O during crystallisation at ~ 4 GPa and 264-276 K. The reflections marked by (*) are due to a small amount of lead which was added to the sample to determine the pressure. The inset shows the pressure variation during crystallisation, derived from the refined lattice parameters of lead.
Figure 2. Pressure/temperature path before crystallisation on the phase diagram of pure water and sketch of ice phases VII and VIII. Red and grey balls designate oxygen and hydrogen, respectively. Ice VII is hydrogen disordered with oxygen on a bcc lattice 9, whereas ice VIII is its hydrogen ordered tetragonal form.
193
Ultrasonic study of epsomite (MgSO4·7H2O) under pressure
E.L. Gromnitskaya*1, O.F. Yagafarov1, A.G. Lyapin1, V.V. Brazhkin1, and A.D. Fortes2,3 1Institute for High Pressure Physics, Russian Academy of Sciences,
Troitsk, Moscow region, 142190, Russia 2Centre for Planetary Sciences at UCL/Birkbeck, Gower Street, London, WC1E 6BT, U.K.
3Dept. Earth Sciences, University College London, Gower Street, London, WC1E 6BT, U.K.
Epsomite (MgSO4·7H2O) is a widespread evaporite mineral on Earth, and may also be an important reservoir of bound water in the regolith of Mars. In addition, epsomite is known to occur as an aqueous alteration product in chondritic meteorites. As a consequence it has been speculated that icy satellites will contain sulfate hydrates in their ice shells, leached from the chondritic cores during differentiation. The phase diagram of epsomite is poorly known even at relatively low pressures, and there is disagreement between various studies [1-3] concerning the sequence of phase transitions under pressure.
Here we report an ultrasonic study of MgSO4·7H2O at 77, 275, 285, and 295 K and of MgSO4·7D2O at 295 K in the pressure range 0 < P < 2.8 GPa. We employ an original experimental facility based on the modified high-pressure piston-cylinder device to map the loci of phase boundaries by making simultaneous measurements of density, bulk modulus, shear modulus and Poisson’s ratio. The measurements were performed by the pulsed ultrasonic method using x-cut, y-cut quartz plates and LiNO3 plates as piezoelectric sensors with carrier frequencies of 5-10 MHz. The phase transitions were detected by jumps in experimental pressure dependencies of the lengths of samples and transit times of ultrasonic waves. At 295 K we have identified three phase transitions at ≈1.4, ≈1.6, and 2.5–2.8 GPa, where the latter transition occurs with a large change in volume and elastic moduli. The elastic properties, and the sequence of phase transitions for MgSO4·7H2O and MgSO4·7D2O, are very similar and correlate quite well, not only with the piston-cylinder measurements of Bridgman [1], but also with the results of high-pressure powder neutron diffraction studies of MgSO4·7D2O [3,4]. At 275 K, we observed only one transition (up to 2.75 GPa) at a pressure ≈1.6 GPa, and observed a different picture of the volume and elastic modulus changes with respect to the 295 and 285 K data. This suggests that the phase transitions in epsomite are strongly temperature dependent; indeed Fortes et al. [3] found that the ambient-pressure phase persisted up to 5.3 GPa even at the relatively modest temperature of 200 K. Reversal of the phase transitions on decompression (from 275 to 295 K) exhibit large hysteresis: in all cases we observed two transitions near 1.2–1.5 and 0.2–0.4 GPa, and the final recovered phase was found by powder X-ray diffraction to be the ambient pressure orthorhombic phase of epsomite. Further in-situ structural studies of the phase transitions are necessary to clarify the polymorphism of epsomite.
[1] P. W. Bridgman, Proc. Am. Acad. Arts Sci. 1948, 76, 71; ibid. 89. [2] L. D. Livshits, Yu. S. Genshaft, and Yu. N. Ryabin, Russ. J. Inorg. Chem. 1963, 8, 676. *3+ A. D. Fortes, I. G. Wood, L. Vočadlo, H. E. A. Brand, P. M. Grindrod, K. H. Joy, and M. G.
Tucker, 37th Lunar and Planetary Science Conference, 2006, abstract #1029. *4+ A. D. Fortes, I. G. Wood, K. S. Knight, M. Alfredsson and L. Vočadlo, Eur. J. Min. 2006, 18,
449.
* E-mail : [email protected] Keywords : Elastic properties, ultrasonic method; epsomite; phase diagram
194
Pressure–induced Raman spectral changes in [DEME][BF4]
Y. Imai1, H. Abe1, T. Goto2, T. Takekiyo2 and Y. Yoshimura2 1Department of Materials Science and Engineering, National Defense Academy, Yokosuka
Kanagawa - 239-8686, Japan 2Department of Applied Chemistry, National Defense Academy, Yokosuka,
Kanagawa 239-8686, Japan
Room Temperature Ionic Liquids (RTILs) are molten salts consisted of only cations and anions. As typical RTILs, there are imidazolium series, pyridinium series and aliphatic series RTILs, and physical properties of the imidazolium series RTILs have been mainly so far investigated[1]. In this study, we have measured Raman spectral changes of a hydrophilic RTIL, N, N-diethyl-N-methyl-N-2-methoxyethyl ammonium tetrafluoroborate, [DEME][BF4], which is one of aliphatic series RTILs.
Raman spectral changes of [DEME][BF4] at room temperature were corrected by using JASCO NR-1800 spectrometer. The 514.5 nm argon ion laser excitation was used. To apply high pressures to the sample, we used a Diamond Anvil Cell (DAC). The sample and few ruby chips were sealed by using a stainless steel gasket in the DAC. By using the pressure dependence of the spectral shift of the ruby chip[2], the applied pressure was determined.
Fig. 1 shows a Raman spectral change in the CH stretching region as a function of pressure. For comparison, we put the Raman spectrum of the [DEME][BF4] in the crystalline state at a normal pressure at the bottom of the figure. At 430 MPa, we found that the sample crystallized upon compression. We note that crystal structures of [DEME][BF4] induced by high pressure and low temperature are totally different from each other in view of the spectral profiles. Additionally, both whole the CH band and the stretching mode of BF4 anion[1] at 760 cm
-1 (Fig. 2) shift to higher
frequencies with increasing pressure. These results indicate that interaction between [DEME] cation and [BF4] anion gets stronger. These ions under high pressures have different configurations and
conformations from the crystal structure at low temperatures. We discuss its results in light of the conformational change of [DEME] cation upon compression.
[1] S. A. Katsyuba, E. E. Zvereva, A. Vidis and P. J. Dyson, J. Phys. Chem. 2007, 111, 352. [2] H. K. Mao, P. M. Bell, J. W. Shaner and D. J. Steinberg, J. Appl. Phys., 1978, 49, 3276.
*E-mail : [email protected] Keywords: RTILs, Diamond Anvil Cell (DAC), pressure-induced phase transitions
Fig. 1 Raman spectral changes in the CH stretching region of [DEME][BF4] as a function of pressure at room temperature.
Fig. 2 Variation of the stretching mode of BF4 anion with increasing applied pressure
195
Pressure-induced phase transition of ice in aqueous KOH solution
Y. Yoshimura*
Department of Applied Chemistry, National Defense Academy, 1-10-20 Hashirimizu, Yokosuka, Kanagawa 239-8686, Japan
In former studies [1-4]
, we reported that the ice phase in aqueous LiCl solution (LiCl・12H2O) transforms to an amorphous phase at 500 MPa
[1, 2], as in the case of pressure-induced
amorphization of ice Ih to a high-density amorphous ice (HDA)[5]
, whereas that the ice phase in aqueous KCl or RbCl solution transforms to a crystalline ice VII’ phase (the frozen-in disorder of ice VII) at 800 MPa
[3, 4]. That the results show differences depending on the salts is very
intuitive, because salts are generally considered to not dissolve interstitially in the ice lattice. On the other hand, it is known that doping with the alkali hydroxides or hydrochloric acid in ice has the remarkable effect of increasing proton mobility at low temperature
[6, 7]; e.g.
Tajima et al.[6]
revealed that a fast dielectric relaxation following an order-disorder phase transition occurs when KOH is doped in ice Ih. However, there have been still few studies of salt impurities in ice at high pressures
In this study, as an extension of the previous studies, we have examined the changes in in situ
Raman spectra of ice in aqueous KOH solution (KOH・12H2O) as a function of pressure at liquid nitrogen temperature (77 K). Here we show that the ice in aqueous KOH probably transforms to low-temperature ice VII’ phase at around 800 MPa. Present results confirmed that there are propensities that the aqueous salt solution to form a glassy state upon cooling becomes an amorphous phase on compression, while that the aqueous salt forming a crystalline state on cooling at a normal pressure transforms to a high-pressure crystalline ice phase, such as ice VII’.
[1] Y. Yoshimura, H. Kanno, J. Phys. Cond. Matt. 2002, 14, 10671. [2] Y. Yoshimura, Proceedings of the 2nd Asian Conference on High Pressure Research, 2005,
achpr-0471. [3] Y. Yoshimura, R. J. Hemley, H. K. Mao, Chem. Phys. Lett. 2004, 400, 511. [4] Y. Yoshimura, Proceedings of the 20th International Conference on High Pressure Science
and Technology, 2005, WIC- O300. [5] O. Mishima, L. D. Calvert, E. Whalley, Nature, 1984, 310, 393. [6] C. G. Salzmann, P. G. Radaelli, A. Hallbruker, E. Mayer, J. L. Finney, Scinece, 2006, 311,
1758. [7] Y. Tajima, T. Matsuo, H. Suga, Nature, 1982, 299, 810.
*E-mail : [email protected] Keywords: Diamond Anvil Cell, Pressure-induced phase transitions, Ice
196
Structural transformation and dynamical properties of barium peroxide at high pressure
I. Efthimiopoulos1, K. Kunc1, G. V. Vajenine1,2, S. Karmakar1, K. Syassen1*, M. Hanfland3
1Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany 2Institut Anorganische Chemie, Universität Stuttgart, D-70569 Stuttgart, Germany
3European Synchrotron Radiation Facility (ESRF), F-38043 Grenoble, France
Barium peroxide BaO2 belongs to the class of ionic solid-state MX2 compounds which contain molecular-like X2 fragments with covalent bonding. All such known MX2 compounds crystallize in one of the variants of the NaCl-type structure with several degrees of deviation from the cubic symmetry depending on the orientation of the X2 moieties. A number of related temperature-induced phase transformations is known *1+. In contrast to ‘nonmolecular’ ionic MX2 compounds (see e.g. [2,3] for summaries), the effect of high pressure on the structure and properties of the MX2 compounds with molecular fragments has not been investigated at all. One expects, however, a number of interesting changes. Similar to the temperature-induced phase transitions, reorientation of the X2 dumbbells within an octahedron of metal atoms is likely under high pressure. Furthermore, an increase in the effective coordination number from 6 (NaCl-based) to 8 (CsCl-based) is expected. Last but not least, oligomerisation and eventually polymerisation of the non-metal atoms is a possibility.
We report here a high-pressure study of BaO2. Tetragonal BaO2 (CaC2-type, I4/mmm) is found to transform to an orthorhombic modification at 35 GPa. The eight-coordinated high pressure phase represents a new structure type. It is related to the CsCl-type structure, but can also be interpreted as a distorted variant of the hexagonal AlB2 type. Besides x-ray diffraction, Raman measurements have been performed to investigate the lattice dynamics of BaO2 under pressure. The experimental observations are compared to results of detailed first-principles calculations of the structural stability and dynamical properties.
[1] U. Ruschewitz, Coord. Chem. Rev. 244, 115–136 (2003). [2] D. G. Pettifor, J. Phys. C: Solid State Phys. 19, 285 (1986). [3] J. M. Leger and J. Haines, Europ. J. Solid State Inorg. Chem. 34, 785-796 (1997).
*E-mail : [email protected]
197
Water-Methane Mixtures at Extreme Conditions
M.S. Lee1, S. Scandolo*1,2 1The Abdus Salam International Centre for Theoretical Physics, Trieste, Italy
2CNR-INFM Democritos National Simulation Center, Trieste, Italy
Understanding the behavior of methane-rich hydrous fluids at extreme conditions of pressure and temperature has far ranging implications in planetary sciences, chemistry, biophysics, and geochemistry. Water and methane are the main constituents of the ``ice" middle layer of Neptune and Uranus, where they form a fluid mixture that undergoes progressive ionization as a function of increasing pressure and temperature along the planetary radius, starting from a few tens of GPa and a few thousand degrees kelvin. Several experimental and theoretical studies have addressed the properties of the individual components, water and methane, but only a few have considered mixtures, particularly at the pressures relevant for ionization [1]. We have simulated by ab-initio molecular dynamics a CH4/H2O mixture at four PT conditions ranging between 15 and 300 GPa, and 1800 and 5000 K. The four PT points are representative of undissociated, partially dissociated, and fully dissociated regimes for water [2]. We find that changes in the water structure have dramatic consequences on the solvation, ionization, and full dissociation of methane. We also find that the mixture becomes electronically conducting at milder PT conditions than pure water.
[1] W.J. Nellis, N.C. Holmes, A.C. Mitchell, D.C. Hamilton, M. Nicol, J. Chem. Phys. 1997, 107, 9096
[2] C. Cavazzoni, G.L. Chiarotti, S. Scandolo, E. Tosatti, M. Bernasconi, M. Parrinello, Science, 1999, 283, 44
*E-mail : [email protected] Ab-initio simulations, Planetary science, Water, Methane
198
The structure of methane, phase A
H.E. Maynard-Casely*, C.L. Bull, M. Guthrie♦, E. Gregoryanz, L.F. Lundegaard, I. Loa, M.I. McMahon, R.J. Nelmes and J.S. Loveday
SUPA, School of Physics and Astronomy, Centre for Science at Extreme Conditions, University of Edinburgh EH9 3JZ
The ices (water, ammonia, methane etc.) provide good systems to explore the interplay between inter and intra-molecular interactions. Methane is the only member of the group to have no hydrogen bonding: its inter-molecular forces are dominated by van der Waals interactions and steric repulsive forces. Methane is also thought to be a major constituent of the interiors of Uranus and Neptune. Resolution of methane’s equation of state and high-pressure behavior would improve modeling of these planets.
Despite methane’s importance for the areas above, much is still unknown about its structures at high pressure. Of the nine phases so far identified [1], none of the high-pressure structures had been solved before the beginning of our studies. Our efforts over the past years have allowed us to determine the carbon structure for phase B with single-crystal x-ray diffraction [2]. We have also completed a low-temperature high-pressure neutron diffraction experiment, the first to probe methane under these conditions [3]. The latter study questioned the segregation of phase A and IV previously suggested by Bini et al. [1]. A conclusion of this is that the phase A structure exists over a wider temperature range than previously thought.
We will present a full structure (carbon and hydrogen) solution of phase A, determined from a combination of x-ray single-crystal and neutron powder data. The implications of this structure will be discussed.
[1] R. Bini and G. Pratesi. Physical Review B 55,14800 (1997). [2] H.E. Maynard, J.S. Loveday, E. Gregoryanz, L.F. Lundegaard, C.L. Bull, M. Guthrie, O.
Degtyareva, and R.J. Nelmes. In Joint 21st AIRAPT and 45th EHPRG Int. Conference, number 0246.
[3] H.E. Maynard, J.S. Loveday, S. Klotz, C.L. Bull, and T.C. Hansen. High Pressure Research, 29:125, 2009.
E-mail : [email protected] Current address: Advanced Photon Source, Argonne National Laboratory, South Cass Ave,
Argonne, Illinois, U.S.A. Keywords: Methane, Planets, X-ray diffraction, Neutron diffraction
199
High-pressure studies of ammonia hydrates
J.S. Loveday*, C.L. Bull, H.E. Maynard-Casely, C. Wilson, M.I. McMahon and R.J. Nelmes
SUPA, School of Physics and Astronomy, Centre for Science at Extreme Conditions, University of Edinburgh EH9 3JZ
In the context of the outer solar system the ices (ammonia, water and methane, and the mixtures thereof) form the basis of the 'mineralogy'. These molecules are believed to account for significant fractions of the masses of Uranus, Neptune, Titan and Triton. The high-pressure properties of these ices is hence of considerable importance to models of the evolution of these bodies. For example, stratification of the icy mantles of Uranus and Neptune has been invoked to explain their unusual non-dipolar magnetic fields
[1]. But there is as yet little
physico-chemical basis for such stratification.
We will describe recent studies of ammonia mono- and di-hydrates (AMH and ADH, respectively). These compositions are both of potential relevance to the outer solar system. In earlier neutron studies of AMH we have found six new high-pressure forms in the pressure range 0-10 GPa
[2], including AMH-VI which has a body-centred cubic (bcc) arrangement of
molecular centres with substitutional disorder of ammonia and water molecules on each site
[3]. However, none of the other structures proved solvable by powder diffraction
techniques. More recently, Fortes et al[4]
, using ab-initio methods, predicted an ionisation transition in ammonia monohydrate from NH3.H2O to NH4+OH- at 5 GPa. Fortes et al have also found evidence that ADH adopts a water-rich version of the substitutionally-disordered bcc structure of AMH-VI, but this was in single sample at low temperatures and they have not been able to reproduce the result in other samples
[5].
We have now carried out studies of ADH which have reproduced Fortes et al's observation of the bcc substitutionally-disordered structure in ADH, but following a different P-T path, and we have shown that this structure can be brought to room temperature at 6 GPa. We have also extended our studies of AMH-V, which forms on compression of liquid AMH at room temperature. We find that the neutron diffraction patterns are unchanged with increasing pressure up to 30 GPa, which suggests that either AMH-V is ionised when it forms from the melt at ~1.5 GPa or that it does not ionise up to 30 GPa. We will also present the preliminary results of an x-ray single-crystal study of AMH-V. We will discuss some of the interesting implications of the results.
[1] S.Stanley and J.Bloxham, Nature 2004, 428, 151. [2]J.S.Loveday and R.J.Nelmes, High Pres. Res. 2003, 23, 41. [3] J.S.Loveday and R.J.Nelmes, Phys. Rev. Lett. 1999, 83, 4329. [4] A.D.Fortes, J.P.Brodholt, I.G.Wood, L.Vocadlo, H.D.E.Jenkins. J. Chem.Phys. 2001, 115,
7006. [5] A.D.Fortes, M.Alfredsson, I.G.Wood, L.Vocadlo, K.G.Knight, W.G.Marshall, M.G.Tucker, and
F.Fernandez-Alonso. High Press. Res 2007, 27, 201.
*E-mail : [email protected] Keywords: hydrogen bonding, neutron diffraction, planetary ices, ammonia hydrates
200
The relationship between Ice VII and Ice VIII
R.J. Nelmes*, ♦M. Guthrie, C.L. Bull, H. Hamidov, K. Komatsu♠, M.I. McMahon, L.F. Lundegaard and J.S.Loveday
SUPA, School of Physics and Astronomy, Centre for Science at Extreme Conditions, University of Edinburgh EH9 3JZ
Ices VII and VIII dominate the high-pressure phase diagram of water below 70 GPa. They have been extensively studied because water is a model hydrogen-bonded system and because of the interest in the transition to proton-centred ice X which begins at ~70 GPa
[1]. However,
there is continuing dispute as to the precise nature of proton-disordered ice VII and its relationship to proton-ordered ice VIII. There are also reports of incommensuration in ice VII, and of discontinuities in the behaviour of both phases in the 15-20 GPa pressure range
[2,3,4].
This is the region where the transition temperature (Tc) between the phases – which at low pressures is pressure independent at ~273 K – begins to fall with increasing pressure, and there are speculations that the nature of the transition changes in this pressure range
[5].
We have previously completed total-scattering studies of ice VII which show that molecular orientations are disordered at nearest-neighbour distances at ~5 GPa, in keeping with measurements of the change in entropy, ΔS, for the transition from ice VIII in the same pressure range, and we plan comparative studies at ~20 GPa. We will also present measurements of the atomic thermal motion, which reveal anomalous behaviour in ice VIII at ~15 GPa that is associated with an anomaly in the behaviour of the c/a ratio – in a range where some recent studies have shown a change in the Raman spectrum
[4]. In contrast, as
reported at EHPRG 2008, our x-ray and neutron studies show no evidence for anomalies in ice VII
[6], contrary to the transition recently reported by Somayazulu et al
[4] Another recent
study[7]
found a very large change in volume per molecule, ΔV, of some 1% at ~20 GPa which implies an improbably large ΔS. We have attempted to make our own measurements and the results probably demonstrate that pressure effects make it very difficult to do. We will discuss this and the interest in measuring ΔS in this higher pressure range, and revisit what is known about the configurational entropy of ice VII and its implications for disorder models.
[1] A.F.Goncharov, V.V.Struzhkin, M.S.Somayazulu, R.J.Hemley and H.K.Mao. Science 1996, 73, 218.
[2] P.Loubeyre, R.le Toullec, E.Wolanin, M.Hanfland and D. Hausermann. Nature 1999, 397, 503.
[3] M.Somayazulu, J.F.Shu, C.S.Zha, A.F.Goncharov, O.Tschauner, H.K.Mao and R.J.Hemley. J. Chem. Phys. 2008, 128, 064510.
[4] Y.Yoshimura, S.T.Stewart, M.Somayazulu, H.K.Mao and R.J.Hemley. J. Chem. Phys. 2006, 124, 024502.
[5] P.Pruzan. J. Mol. Struc. 1994, 322, 279. [6] R .J. Nelmes, Poster EHPRG 46 2008, Valencia. [7] H.Yamawaki, H.Fujihisa, M.Sakashita, A.Nakayama and K.Aoki, Physica B 2004, 344, 260.
*E-mail : [email protected] Current address: Advanced Photon Source, Argonne National Laboratory, South Cass Ave,
Argonne, Illinois, U.S.A. Current address: Laboratory for Earthquake Chemistry, University of Tokyo, Japan
Keywords: Ice, hydrogen bonding, Phase Transition, Configurational Entropy
201
Sound velocity of an equimolar N2/CO2 mixture at high pressure and high temperature
S. Ninet1*, G. Weck2 and P. Loubeyre2 1 IMPMC, 140 rue de Lourmel, 75015 Paris, France
2 CEA, Bruyères le Châtel, France
The high pressure phase diagram of N2/CO2 mixture is of importance for geologists because such mixtures have been frequently detected in rock inclusions - granulites and eclogites – in the lower crust. The interpretation of these data require precise knowledge on the high pressure-high temperature properties of N2-CO2 mixture. In particular, a fluid-fluid immiscibility was predicted [1] in an equimolar mixture but not observed experimentally up to 5 GPa and 400 K [2].
In this poster, we will present precise measurements of sound velocity “vs” of an equimolar mixture N2-CO2 in the thermodynamic range [0-15 GPa] and [300-700K] using a resistively heated diamond anvil cell. No fluid-fluid immiscibility was detected by visual observations. The refractive index “n” and the product “nvs” were respectively determined in fluid phase by interferometric measurements and Brillouin scattering along several isotherms. The sound velocity was deduced and compared to an ideal mixture model.
[1] R. Thiéry, A.M. Van den Kerkhof and J. Dubessy, Eur. J. Mineral, 6, 753 (1994)
[2] M.E. Kooi, J.A. Schouten, A.M. Van der Kerkhof, G. Istrate and E. Althaus, Geochimica abd Cosmochimica acta, 62, 2837 (1998)
*Email: [email protected] High pressure mixture, N2-CO2 mixture, sound velocity
202
Size-driven phase diagram in TGS crystals under high hydrostatic pressure. S. Waplak*, J. Stankowski, W. Jurga and M. Krupski
Institute of Molecular Physics, Polish Academy of Science, Poznań, Poland
For ferroic materials, size effects are of keen interest for practical as well as scientific reason. As is has been predicted by Landau theory a spontaneous polarization in ferroelectrics becomes zero below some critical size.
We have studied the influence of high hydrostatic pressure up to 2.5 GPa on dielectric
parameters Ps, Ec, max and Tc in TGS crystals. Above critical pressure pc 1.8 GPa the damage process of avalanche type called by us as “ferroelectric catastrophy” appears and Tc(p) dependence follows the equation:
𝑇𝐶 = 𝑇𝑐𝑚𝑎𝑥 1 − 𝐶
𝑃 − 𝑃𝑐𝑃𝑐
1𝑛
with n = 0.33 as the feature of 3D-2D transformation. Numerous of our date allow us to built phase diagram for TGS under high pressure. Based on dielectric and EPR data of TGS with paramagnetic dopant, the term “superparelectric” limit is postulated for critical size of TGS particle.
This work was supported by N N202 1206 33 grant.
*Email : [email protected] Keywords :TGS, EPR, dielectric, high pressure
203
Influence of the high hydrostatic pressure on the ferro–paraelectric phase transition in TGS crystal.
W. Jurga*, J. Stankowski, M. Krupski and S. Waplak
Institute of Molecular Physics, Polish Academy of Science, Poznań, Poland
The dielectric spectroscopy studies of TGS crystal were carried out at various pressures up to
2.5 GPa. The modified Curie-Weiss law are used to describe 1/dependence versus temperature at different pressure as for relaxor ferroelectrics / dielectrics [1]:
1
𝜀=
1
𝜀𝑚𝑎𝑥
1 + 𝑇 − 𝑇𝑚𝑎𝑥 𝛾
2∆2
where corresponds to the degree of relaxation and is the broadening parameter. In the
vicinity of 1.8 GPa we have observed a continuous change of from 1 to 2. It may indicate that in result of crystal structure “damage” the dielectric response tends to relaxor type.
This work was supported by N N202 1206 33 grant.
[1] I. Rivera, A. Kumar, N. Ortega, et al. Solid State Communications 149 (2009) 172-176
*Email : [email protected] TGS, dielectric, high pressure
204
205
Nanosciences
Lectures Raman Spectroscopy of Carbon Nanotubes under Pressure ______________________ 207
Nanocrystals of ZnO formed by the hot isostatic pressure (HIP) method ____________ 208
Transport properties of individual carbon nanotubes under high pressure __________ 209
Pressure-induced phenomena in single-walled carbon nanotubes probed by
infrared spectroscopy ______________________________________________ 210
Posters NS 01 : Electronic properties of C60@SWCNTs bundle under hydrostatic pressure ____ 211
NS 02 : Phase transformations in fullerite C60 and single-wall carbon nanotubes
at pressures 20 - 50 GPa found from conductivity _______________________ 212
NS 03 : In situ synchrotron diffraction study of high-pressure C60 polymerization ____ 213
NS 04 : High pressure Raman study of graphene and 3-layer graphite _____________ 214
NS 05 : Fullerenes under high multi-shock pressures ____________________________ 215
NS 06 : Hydrofullerene C60H36 under high-pressure short-time conditions ___________ 216
NS 07 : Pressure dependence of Raman modes in DWCNT Filled with 1D CdSe
Nanowires _______________________________________________________ 217
NS 08 : Measurements of C70 fullerite shock compressibility with the use of
synchrotron radiation technique _____________________________________ 218
NS 09 : High pressure Raman study of peapod and CVD grown double wall
carbon nanotubes _________________________________________________ 219
NS 10 : Optical absorption under high pressure on zinc-blende Yb3+
-doped CdS
nanoparticles ____________________________________________________ 220
NS 11 : Raman study of H2 stuffed into nano space of graphite under high
pressure _________________________________________________________ 221
NS 12 : The ac impedance of single wall carbon nanotubes at high pressures _______ 222
NS 13 : Double wall carbon nanotubes at high pressures: doping effects ___________ 223
NS 14 : Soft-extrusion-related updated bottom-up approach to bulk,
nanostructured materials processing _________________________________ 224
NS 15 : Transport properties of strained graphene _____________________________ 225
NS 16 : Raman studies on Li4C60 and Na4C60 polymer under high pressure ___________ 226
206
207
Raman Spectroscopy of Carbon Nanotubes under Pressure
D.J. Dunstan and A.J.Ghandour
Physics Dept, Queen Mary University of London, London E1 4NS, England
The Raman frequencies of carbon nanotubes generally move to high frequenies with pressure. However, the experimental data has been very confusing, with a wide variety of pressure coefficients, quenching pressures, and breakpoints between initial high pressure coefficients and the lower coefficients observed at high pressure. Little consistency has been seen and correlation with experimental parameters has been difficult. Concentrating on the G-band, we will review the key results in the literature, leading up to our observation[1] that the different results obtained by changing the excitation energy are due to the different resonance conditions and their changes with pressure. New experimental data are reported, comparing hexane and water/methanol as the pressure-transmitting medium (solvent). The effects of changing the solvent can again be understood in terms of changes of the resonance conditions.
[1] Ghandour et al., Phys Rev B78, 045413 (2008)
208
Nanocrystals of ZnO formed by the hot isostatic pressure (HIP) method
J. González*1,2, J. Marquina3, F. Rodríguez1 and R. Valiente4 1MALTA Consolider Team, DCITIMAC, Facultad de Ciencias,
Universidad de Cantabria, Santander, Spain 2Centro de Semiconductores, Universidad de los Andes, Mérida, Venezuela 3Centro Avanzado de Óptica, Universidad de los Andes, Mérida, Venezuela
4MALTA Consolider Team, Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Cantabria, Santander, Spain
With a direct band gap of 3.4 eV at ambient conditions, wurtzitic ZnO (w-ZnO), like GaN or 6H-SiC, is intensively studied in view of potential applicability in the field of opto- electronics (eg, laser or light–emitting diodes). Furthermore, in comparison with its previous competitors, w–ZnO combines several unique electrical, acoustic, and chemical properties, which make it one of the most technologically relevant binary compounds. The interest in semiconductors which are spatially confined to a few tens of nanometers has increased in recent years. Three dimensionally confined electron-hole systems, known as quantum dots (QD), have unusual optical properties that may lead to greatly improved opto–electronic devices. Phonon confinement occurs when d (diameter) is small enough to consider the phonon described by a wave packed instead of a plane wave. Several high-pressure structural investigations of ZnO have been done in the last two decades and all agree that the w–ZnO to NaCl–ZnO phase transition is reversible at ambient temperature (with a transition pressure of 9 GPa upon increasing pressure and 2 GPa upon decreasing pressure). The transition is a first–order reconstructive transition with a 20 % increase in density and a change in coordination number from 4 to 6.
We present here a novel and simple physical method for obtaining ZnO nanocrystals using the hot-isostatic pressure cycle method up to 13 GPa at 500 K. The nanocrystals were synthesized from single crystals of ZnO which are pressurized in a membrane diamond anvil cell (MDAC). The MDAC was surrounded by a heater and a thermocouple was glued on one end of the diamond anvil to determine the average temperature on the sample with an accuracy of 20 K. BN powder was used as a pressure transmitting medium because it is chemically inert in this temperature range. The pressure was measured with the ruby luminescence method. Once loaded, the cell was heated to 500 K and the pressure was increased up to 13 GPa (NaCl Phase) and after that the pressure was decreased to the atmospheric value and finally we decrease the temperature to 300 K. The recovered nanocrystals in the wurtzite phase (w–ZnO) were characterized by high resolution Raman scattering and XRD studies. The Raman spectrum of high quality ZnO single crystal and nanocrystals were compared and we observed both the softening and the asymmetric broadening of Raman peaks which are in good agreement with the effect of relaxation of the q–vector selection rule due to quantum size confinement effect. The experimental results confirm the existence of ZnO nanocrystals in the wurtzite phase with a diameter of the order of 17 nm.
*E-mail : [email protected] Keywords: nanocrystals, raman scattering, phase transitions, large gap semiconductors
209
Transport properties of individual carbon nanotubes under high pressure
C. Caillier1, A. Ayari1, V. Gouttenoire1, J.-M. Benoit1, V. Jourdain2, M. Picher2, M. Paillet2, S. Le Floch1, J.-L. Sauvajol2, and A. San Miguel1*
1Laboratoire PMCN, CNRS, UMR 5586, Université Lyon 1, F-69622 Villeurbanne, France 2Univ Montpellier 2, CNRS UMR 5587, Lab Colloides Verres & Nanomat, 34095 Montpellier
Carbon nanotubes are interesting candidates to fabricate nanoelectronic systems, because of their size and their ability to be either metallic or semiconductive
[1]. With back gates, this
allows to build metallic wires and transistors at the nano scale. Moreover, their high resilience
[2] also allows electronmechanical applications using strain dependences
[3] and the
vibration of the tubes[4]
.
Pressure is also an interesting parameter that can be used to tune the electronic properties[5]
. Indeed, on one side nanotubes can resist reversibly to pressure as high as 40 GPa
[6,7], and on
the other side, the electronic properties highly depend on the atomic structure[1]
which itself is sensitive to pressure
[8].
In this work we have investigated the transport properties of several types of contacted individual carbon nanotubes under high pressure. Namely, we studied metallic tubes, semiconductive ones, and one ambipolar multi-walled nanotube. We find that pressure can have strong effects on the devices’ properties, depending on the nature of the contacted tube.
The results are compared to some simple calculations, and discussed considering the physics of the contacts and the gate voltage hysteresis, as well as the Schottky barriers and the nanotube intrinsic properties.
[1] N. Hamada, S. Sawada, and A. Oshiyama, Phys. Rev. Lett, 1992, 68, 1579. [2] M.R. Falvo, G.J. Clary, R.M. Taylor II, V. Chi, F.P. Brooks Jr, S.Washburn, R. Superfine.
Nature, 1997, 389, 582. [3] J. Cao, Q. Wang, and H. Dai, Phys. Rev. Lett, 2003, 90, 157601. [4] K. Jensen, J. Weldon, H. Garcia, and A. Zettl, Nano Letters, 2007, 7, 3508. [5] R. B. Capaz, C. D. Spataru, P. Tangney, M. L. Cohen, and S. G. Louie, phys. stat. sol. (b),
2004, 241, 3352. [6] A. Merlen, N. Bendiab, P. Toulemonde, A. Aouizerat, A. San Miguel, J. L. Sauvajol, G.
Montagnac, H. Cardon, and P. Petit. Phys. Rev B, 2005, 72 035409. [7] Ch. Caillier, D. Machon, A. San-Miguel, R. Arenal, G. Montagnac, H. Cardon, M. Kalbac, M.
Zukalova, and L. Kavan, Phys. Rev. B, 2008, 77, 125418. [8] S. Chan, W. Yim, X.G. Gong, and Z. Liu, Phys. Rev. B, 2003, 68, 075404.
*E-mail : [email protected] Keywords: Nanotube, Electronic, Carbon, Pressure
210
Pressure-induced phenomena in single-walled carbon nanotubes probed by infrared spectroscopy
A. Abouelsayed1, K. Thirunavukkuarasu1, K. Kamarás2, F. Hennrich3, C. A. Kuntscher*1
1 Experimentalphysik II, Universität Augsburg, D-86159 Augsburg, Germany 2Research Institute for Solid State Physics and Optics, Budapest, Hungary
3Institut für Nanotechnologie, Forschungszentrum Karlsruhe, D-76021 Karlsruhe, Germany
The study of single-walled carbon nanotubes (SWCNTs) under high pressure has attracted much interest recently as the application of pressure induces structural deformations of the SWCNTs and also tunes the intertube interactions by changing the distances between the tubes. Both should significantly affect the properties of the SWCNTs. Optical absorption of SWCNTs being direct indication of their electronic properties, is a sensitive probe for investigating the electronic structure of SWCNTs.
Therefore, pressure-dependent infrared transmission measurements on unoriented SWCNT films were performed over a broad frequency range (120-22000 cm
-1) for pressures up to 8
GPa. Different pressure transmitting media have been employed for the pressure-dependent transmission measurements to verify their influence on the observed pressure dependence. A clear redshift of the higher-energy optical absorption bands which correspond to transitions across the van Hove singularities are observed with the application of pressure. Irrespective of the pressure transmitting medium, the pressure-induced frequency shifts of the optical transitions show an anomaly at a critical pressure Pc=2-3 GPa. This anomaly is related to a structural phase transition, where the nanotubes' cross-section changes from circular to oval.
In this presentation, we discuss in detail the most important observations and its implications towards the various pressure-induced phenomena in SWCNTs
Supported by the DFG, Emmy Noether-program. Provision of beamtime at the ANKA Angströmquelle Karlsruhe is acknowledged.
*E-mail : [email protected] Keywords: Infrared spectroscopy, single-walled carbon nanotubes, optical absorption, pressure-induced phenomena.
211
Electronic properties of C60@SWCNTs bundle under hydrostatic pressure
E.N. Paurá1, V. Lemos2, S. Guerini1 1Departamento de Física,Universidade Federal do Maranhão, Av. dos Portugues,
Campus do Bacanga, CEP 65.085-580, São Luís, MA, Brazil 2Departamento de Física, Universidade Federal do Ceará, Caixa Postal 6030, Campus do Pici,
CEP 60455-670, Fortaleza, CE, Brasil
The interest in materials in the nanometric scale is dramatically increasing, primarily due to their potential application in various scientific and technological fields. Through the improvement of experimental techniques and the development of ever more sophisticated computers theoretical and experimental researchers have had the opportunity and ability to work together. Nanostructures based on carbon nanotubes have been in the forefront of nanomaterial research in the last years [1]. Single wall carbon nanotubes (SWCNTs), with their excellent mechanical and physics properties constitute the prototype for nanoscience in general. In the solid forms, the fullerenes and nanotubes are constituent units weakly bounded to each other. Interesting forms of solid carbon has been synthesized, among which the fullerenes aligned in a chain and encapsulating into carbon nanotubes. These new structures, called peapods (C60@SWCNT), answer for a great part of the recent investigation in nanoscience [2]. Their electronic structures near the Fermi level are controlled by the interunit space and the distribution of the nearly free electron states. In this work the atomic structure and band structure of the C60@SWCNT bundles subjected to hydrostatic pressure are investigated, in order to optimize their properties for possible applications as nanodevices. The calculations were performed in the framework of ab initio density functional theory, based upon norm-conserving pseudopotentials. Generalized gradient approximation has been applied in order to describe the exchange and the correlation functional [3]. The electronic, structural properties and cohesive energy of the C60@SWCNT bundles were obtained.
[1] S. Iijima, Nature (London), 1991, 354, 56. [2] B. W. Smith, M. Monthioux, D. E. Luzzi, Nature (London), 1998, 396, 323. [3] ] P. Ordejon , E. Artacho and J.M. Soler, Phys. Rev. B 53, 10441 (1996).
*E-mail : [email protected] Keywords: pressure, carbon nanotube, fullerene, DFT, peapods.
212
Phase transformations in fullerite C60 and single-wall carbon nanotubes at pressures 20 - 50 GPa found from conductivity
G.V. Tikhomirova*, Ya.Yu.Volkova, A.N. Babushkin
Physics Department, Ural State University, Ekaterinburg, Russia
Conductivity of fullerite C60 and single-wall carbon nanotubes (SWNT) have been studied at pressures 20-50 GPa and temperatures 77-400 K. The kinetics of resistivity of C60 at changing pressure was also studied.
High pressures have been generated in the high-pressure cell with synthetic carbonado-type diamond anvils. The anvils are good conductors and can be used as electric contacts making possible to measure temperature and pressure dependences of resistance. The method used allows us to study the same sample at successive increasing and decreasing pressure.
Resistivity peculiarities were identified with the known phase transitions of fullerite. Successive phase transitions of fullerite C60 appeared in the course of HPHT treatment were accompanied by changes in resistance, which can be of quite different magnitude (from hundreds Ohm to hundreds MOhm) and of different temperature dependence. Critical pressures for the transitions depended on conditions and duration of preliminary HPHT treatment. This fact, as well as smeared character of the transitions is connected with long relaxation time, which was found to be about 140 min.
Three types of SWNT samples were investigated: samples produced by the graphite thermal dispersion method (SWNT percentage is 40 %), the chemical vapor deposition method (SWNT percentage is 80 %) and HiPco method (SWNT percentage is 90 %).
Electric properties of the samples under high pressure were dependent on SWNT percentage. The electric characteristics of SWNT samples remained of the same character with the increasing of SWNT percentage, but the additional features appeared (intermediate region on the temperature dependences of resistance; additional extremums in the baric dependences of activation energy in the pressure range of 40-45 GPa). Thus, the dependences obtained are connected with electric characteristics of SWNT and not with the impurities contained in the sample.
The irreversible changes of the electric properties of the samples observed in the pressure range 27-45 GPa can be connected with both the structure modification and partial destruction of the sample.
This work was supported in part by CRDF grant Y4-P-05-16, and RFBR grant 09-02-01316-а.
* E-mail : [email protected] Keywords: fullerite C60, single-wall carbon nanotubes, conductivity, high pressures
213
In situ synchrotron diffraction study of high-pressure C60 polymerization
L. Marques*1,M. Mezouar2, J-L. Hodeau3 1Departamento de Física and CICE.CO, Universidade de Aveiro,
Campus de Santiago, P-3810-193 Aveiro, Portugal 2European Synchrotron Radiation Facility, 38041 Grenoble, France
3Institut Néel C.N.R.S. BP166 Cedex09, 38042 Grenoble, France,
High-pressure high-temperature polymerization of C60 was followed by in situ synchrotron angular-dispersive diffraction. The Paris-Edinburgh press with WC anvils was employed, being 8 GPa the maximum pressure reached on this study, and the data was collected in 2D MAR detector. Final pressure-temperature conditions were reached through two different thermodynamic paths: a) the pressure-temperature (PT) path involves the compression to the final pressure followed by the temperature raising and b) the temperature-pressure (TP) path in which the compression is applied after the temperature. In both paths high-pressure phases were quenched to room conditions by depressurizing after the temperature shut-down.
The PT path leads to well ordered polymers, highly-oriented (single crystal-like) samples corresponding essentially to mixtures of tetragonal and rhombohedral 2D C60 polymers, although rhombohedral single-phase samples are obtained for pressures above 5 GPa. In contrast, the TP path leads to poor ordered, partially polymerized, samples. Diffraction images collected during the polymerization process shows that the polymerization proceeds along the cell compression axis, i.e. along the uniaxial stress component. In each random oriented grain the polymerization occurs in near-neighbor direction close, or parallel, to the uniaxial stress direction. The transformed samples are then aligned, displaying transformation textures, although no grain rotation occurs. On the other hand, this observation clearly shows that polymerization in C60 is extremely sensitive to the anisotropic stress, which is crucial to select the polymerization direction. A more detailed discussion of the polymerization process will be given at the Meeting.
[1] L. Marques, M. Mezouar, J-L. Hodeau, and M. Núñez-Regueiro, Phys. Rev. B 2003, 68, 193408.
[2] L. Marques, M. Mezouar, J-L. Hodeau, and M. Núñez-Regueiro, Phys. Rev. B 2002, 65, 100101.
*E-mail : [email protected] Keywords: C60, high-pressure polymerization, phase diagram
214
High pressure Raman study of graphene and 3-layer graphite
J. Nicolle*, D. Machon, P. Poncharal, A. San Miguel
Laboratoire de Physique de la Matière Condensée et Nanostructures, CNRS and Université Lyon 1, Villeurbanne France
Graphene is attracting a lot of interest, due to its mechanical and electronic properties at ambient conditions. Indeed electron ballistic transport in one or several layers opens new fields of application in electronics. Furthermore, graphene is the primitive form of the others nanomaterials as nanotubes, and fullerenes. Thus understanding the properties of graphene may open new ways for exploring the physical properties of other nanomaterials. Up to now graphene has been studied in different conditions of temperature, and in vaccum, but never under high pressure.
We present a high pressure Raman study of a graphene sample, and of a 3-layer one. We used a diamond anvil cell, and a standard mixture of methanol:ethanol (4:1) as Pressure Transmitting Medium (PTM). We have followed the evolution of the Raman G band 1580 cm
-1) and the 2D band as a function of pressure [1]. These results are compared, with the
corresponding evolution of the Raman spectra [2], and with our experimental results on graphite using an alcohol mixture and argon as PTM.
[1] Andrea C. Ferrari, solid states communications, 2007, 143, 47. [2] M. Hanfland, H. Beister, K. Syassen, Phys. Rev. B 2008, 39, 12598-12603.
*E-mail : [email protected] Keywords: Graphene, Raman spectroscopy
215
Fullerenes under high multi-shock pressures
V.V. Avdonin *,A.N. Zhukov, G.V. Shilov, V.A. Volodina,A.M. Molodets, Yu.M. Shulga, V.E. Fortov
IPCP RAS, Chernogolovka, Russia
The present work is devoted to a versatile research of electrophysical and thermodynamical properties of C60 and C70 fullerenes under a high multi-shock pressures. Our multi-shock experiments has shown that C60 and C70 fullerenes is preserving its crystal structure and molecules under a dynamic loading up to 30 GPa unlike the high static pressure conditions
[1].
The measurements of an electroconductivity of C60 and C70 fullerenes under these conditions was carried out. It is experimentally established that decreasing of a conductivity of C60 and C70 fullerenes has been changed by a sudden increasing one under the pressure of multi-shock compression above 20 GPa. A semiempirical equation of the state
[2] of C60 and C70
fullerenes was constructed. The analysis of the thermodynamic fullerenes conditions under the high multi-shock pressures was done with help of a present EOS.
Thus, at the present work we found that the crystal and molecular structure of C60 and C70 fullerenes demonstrates a stability under short (microsecond) high multi-shock loading. The data of crystal form properties of C60 and C70 fullerenes under such extreme conditions unachievable under static loading has been obtained.
The work is supported by the program of Presidium of Russian Academy of Sciences “Investigations of a matter under extreme conditions”.
[1] W. Qiu, S. Chowdhury, R. Hammer, N. Velisavljevic, P. Baker, Y. K. Vohra, High Pressure Research, 2006, 26, 3, 175-183.
[2] Molodets A.M., Shakhray D.V., Golyshev A.A., Babare L.V., Avdonin V.V., High Pressure Research, 2006, 26, 3, 223-231.
*E-mail : [email protected] Keywords: fullerene, shock wave, high pressure, conductivity
216
Hydrofullerene C60H36 under high-pressure short-time conditions
A.M. Molodets*, D.V. Shakhray, A.S. Savinykh
Institute of Problem of Chemical Physics, 142432, Chernogolovka, Russia
In the previous work [1] the structure of hydrofullerene C60H36 has been investigated after shock loadings. It has been shown, that hydrofullerene keeps the molecular structure (see Fig. 1) and the crystalline structure (see Fig. 2) under the high-pressure short-time conditions.
The purpose of this work was to study the hydrofullerene C60H36 under shock-wave loading in situ. The sample 1 (see Fig. 3) in the form of a disk was located between two copper disk anvils 2 and 3 and was loaded by aluminum projectile 4 practically as well as in work [1]. The free surface velocity W of the back anvil 2 was registered with the help of VISAR. The source information as time profile W(t) is presented in Fig. 4 by the bold gray line.
The hydrocode simulation (1,2 and 3 lines in Fig.4) allows to choose the set of fitting parameters for the C60H36 hydrofullerene equation of state which give the best profile 2.
[1] A. M. Molodets, et al. Doklady Physics, 2008, Vol. 53, No. 11, pp. 562–565.
*E-mail : [email protected] Keywords: fullerene, shock waves, equation of state, high-strain-rate phenomena
Fig.1. IR spectra of pristine hydrofullerene (1) and shocked (2, 3) at the maximum pressure of 27 and 42 GPa, respectively.
Fig.2. X-ray diffractograms of hydrofullerenes C60H36 (1) in the initial state and (2, 3) after shock loading to 27 and 42 GPa, respectively.
Fig.3 The scheme of the loading and measurement of W(t)
Fig.4. The experimental profile under multi shock wave loading up to 27 GPa. 1,2 and 3 are the simulated profiles.
217
Pressure dependence of Raman modes in DWCNT filled with 1D CdSe nanowires
E. Belandria1, Ch. Power2, S. Nanot3, M. Millot3, J.M. Broto3, E. Flahaut4, F. Rodríguez5, R. Valiente6 and J. González2,5*
1Centro Avanzado de Optica, Facultad de Ciencias, Universidad de los Andes, Merida, Venezuela
2Centro de Semiconductores, Facultad de Ciencias, Universidad de los Andes, Merida, Venezuela
3Laboratoire National des Champs Magnetiques Intenses (LNCMI) - CNRS UPR 3228,Universite de Toulouse, 143 Avenue de Rangueil, 31400 Toulouse, France
4CIRIMAT-LCMIE, UMR CNRS 5085, Université Paul Sabatier, 118 Route de Narbonne, 31077 Toulouse Cedex 4, France
5MALTA Consolider Team, DCITIMAC, Facultad de Ciencias, Universidad de Cantabria, Santander, Spain
6MALTA Consolider Team, Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Cantabria, Santander, Spain.
The synthesis of mono-dimensional nanocrystals is complex due to the lack of stability of such structures. One way to stabilise the nanowires is to prepare them within a container, such as a carbon nanotubes (CNT) due to their inner diameter in the nanometer range, as well as their good chemical and thermal stability. In this work, we have followed a novel approach to the filling of double-wall carbon nanotubes (DWNTs) in wich the external wall protects the internal one, which maintains its structure and chemical and physical properties and in this fabrication process the capillary effect was used to fill DWCNTs with CdSe semiconductors. The samples are characterized by HRTEM, SAED, and Raman spectroscopy. The experimental structural results indicate the presence of CdSe nanowires inside de DWCNTs, with 1.5 nm average internal diameter and 2.2 nm average external diameter and we also observed that the nanotubes were partial CdSe filled (about 60 %) and the length of encapsulated grains are always bigger than the diameter of the inner DWCNTs. Raman spectra of tangential modes of DWNTs filled with 1D nanocrystallin CdSe excited with 514,5 nm were studied at room temperature and elevated pressure up to 16 GPa. The tangential optical phonon modes of the carbon nanotubes are sensitive to the in plane stress and split into a contribution associated with the external and internal tube. Up to 6 GPa we find a pressure coefficient for the internal tube of 5,7 cm
-1GPa
-1 and for the external tube of 6.6 cm
-1GPa
-1. The corresponding Raman
features of the internal tubes appear to be less sensitive to pressure. In the range 6 to 10 GPa we observed a change in the slope of the pressure dependence of the frequency of the tangential modes (3,5 cm
-1GPa
-1 for the outer tube and 2,2 cm
-1GPa
-1 for the inner one) . This
phase transition is associated to a possible structural distortion of the nanotube cross-section. When increasing the pressure furthermore up to 16 GPa the pressure coefficients for the tangential modes associated to the internal and external tubes are the same (10 cm
-1GPa
-1).
*E-mail : [email protected] Keywords: carbon nanotubes; nanowires; confinement; Raman Scattering
218
Measurements of C70 fullerite shock compressibility with the use of synchrotron radiation technique
V.V. Milyavskiy1*, K.A. Ten2,3, T.I. Borodina1, E.R. Pruuel2, B.P. Tolochko4, V.V. Zhulanov3
1Joint Institute for High Temperatures of RAS, Moscow, Russia 2Lavrentyev Institute of Hydrodynamics SB RAS, Novosibirsk, Russia
3Institute of Nuclear Physics SB RAS, Novosibirsk, Russia 4Institute of Solid State Chemistry and Mechanochemistry SB RAS, Novosibirsk, Russia
Shock compressibility of C70 fullerite was measured with the use of pulsed-periodical source of synchrotron radiation of the Institute of Nuclear Physics SB RAS. The starting C70 specimens were prepared by high (1 GPa) hydrostatic pressure treatment and had a density of 1.65 g/cc, a diameter of 15 mm and a thickness of 2.5-3.5 mm. Specimens were loaded by impacts of metal plates (with a diameter of 16 mm) accelerated by high explosives up to velocities of 1.3-1.8 km/s. Synchrotron radiation technique [1] was used to measure the parameters of the shock-compressed fullerite. This method of measurements is based on visualization of movement of density discontinuities by measuring a degree of attenuation of synchrotron radiation by an explored material during passage of shock waves through this material. Positions of the discontinuities were determined each 250 ns. It was obtained that the experimental Hugoniot of C70 fullerite in the explored pressure range (6.3-9.3 GPa) is allocated below the experimental Hugoniot of C60 fullerite [2] on pressure - specific volume plane. The work was supported by RFBR (07-02-00625). The authors thank O.B. Tsiok and L.G. Khvostantsev (IHPP RAS) for high hydrostatic pressure treatment of the specimens.
[1] K.A. Ten, O.V. Evdokov, I.L. Zhogin, V.V. Zhulanov et al, Nucl. Instr. and Meth. in Phys. Res. A 543, 170 (2005).
[2] V.V. Milyavskiy, A.V. Utkin A.Z. Zhuk, V.V. Yakushеv, V.Е. Fortov, Diamond and Relat. Mat. 14, 1920 (2005).
*E-mail : [email protected]
219
High pressure Raman study of peapod and CVD grown double wall carbon nanotubes
J. Arvanitidis1,2*, D. Christofilos2, G. A. Kourouklis2, S. Ves3, T. Takenobu4, Y. Iwasa4, H. Kataura5
1Department of Applied Sciences, Technological Educational Institute of Thessaloniki, 57400 Sindos, Greece
2Physics Division, School of Technology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
3Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece 4Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 and CREST, Japan Science and Technology Corporation, Kawaguchi 332-0012, Japan
5National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562, Japan
The mechanical and transport properties of carbon nanotubes, both of great importance for fundamental research and nanotechnology applications, are determined by the structural characteristics of the individual tubes and their tube-tube van der Waals interaction. A double-wall carbon nanotube (DWCNT) is an archetypal system for studying encapsulation effects in carbon nanotubes, while high pressure application is a unique tool for the investigation of their mechanical and structural stability. Moreover, Raman spectroscopy, due to its size-dependent resonance nature in these materials, allows the selective probing of specific tubes
[1]. In the present work, we investigate the pressure response of bundled
double-wall carbon nanotubes, synthesized following either the C60-peapod conversion process (peapod-DWCNTs)
[2] or their catalytic chemical vapor deposition from ethanol (CVD-
DWCNTs)[3]
, by means of Raman spectroscopy utilizing several excitation wavelengths. We focus on the high frequency region where the G band, corresponding to the tangential carbon stretching vibrations, is located.
The use of different excitation energies probes different internal and external tubes. The former tubes are in all cases mainly semiconducting, while the latter are mainly semiconducting for CVD-DWCNTs (for all the excitation energies used) and peapod-DWCNTs (for the 2.41 eV excitation) or metallic for peapod-DWCNTs (for the 1.83, 1.92 and 1.96 eV excitations). In both samples, the pressure slopes for the low (G
-) and the high frequency (G
+)
G band components for the external tubes are similar to each other and much larger than those for the internal tubes. This reflects the pressure screening effect in the interior of the external tubes irrespectively of their metallic or semiconducting nature
[4]. In the case of the
CVD-DWCNTs with the 2.41 eV excitation, we observe G- components having nearly zero (or
even slightly negative) initial pressure slopes. This is in accordance with the larger mean intratube spacing -stronger pressure screening- in this system compared to that in peapod-DWCNTs
[5].
[1] M. S. Dresselhaus, G. Dresselhaus, R. Saito, A. Jorio, Phys. Rep. 2005, 409, 47. [2] S. Bandow, M. Takizawa, K. Hirahara et al., Chem. Phys. Lett. 2001, 337, 48. [3] K. Iakoubovskii, N. Minami, T. Ueno et al., J. Phys. Chem. 2008, 112, 11194. [4] J. Arvanitidis, D. Christofilos, K. Papagelis et al., Phys. Rev. B 2005, 71, 125404. [5] R. Pfeiffer, H. Peterlik, H. Kuzmany et al., Phys. Status. Sol. (b) 2008, 245, 1943.
*E-mail : [email protected]
220
Optical absorption under high pressure on zinc-blende Yb3+-doped CdS nanoparticles
R. Martín-Rodríguez1 , R. Valiente1, F. Rodríguez2 and J. González2,3 1MALTA Consolider Team, Departamento de Física Aplicada, Facultad de Ciencias,
Universidad de Cantabria, Santander, Spain 2MALTA Consolider Team, DCITIMAC, Facultad de Ciencias,
Universidad de Cantabria, Santander, Spain 3Centro de Semiconductores, Universidad de los Andes, Mérida, Venezuela
Yb3+
-doped CdS nanoparticles have been prepared by the following mechano-chemical reaction NaClYbCdSNaClSNaYbClCdCl 12:10 3
232 in a planetary ball mill.
X-ray diffraction (XRD) patterns of CdS nanoparticles confirm that the prepared samples present pure cubic zinc-blende single phase (zb-CdS) instead of the thermodynamically favored hexagonal wurtzite structure (w-CdS). The Williamson-Hall equation was used to estimate the average crystallite sizes from XRD diagrams. The average particle size of the nanoparticles was estimated to be about 5 nm. Electronic structure calculations in w- and zb-CdS have shown that the fundamental direct band gaps in both structures differ by less than 0.1 eV [1]. Because the excitonic Bohr radius in bulk CdS is of the order of 3 nm we are in the very weak quantum confinement regime for 5nm zb-CdS nanocrystals and therefore the direct optical energy gaps are similar (Eg= 2.40 eV at 300 K). High pressure optical studies indicated an abrupt red-shift in the optical absorption edge at 2.7 GPa and this was identified to be due to a first-order phase transitions [2]. XRD studies showed that bulk wurtzite crystals transform to the rock-salt structure at 2.7-3.0 GPa and the phase transition pressure is very similar for the zinc-blende to rock-salt structure (3.1 GPa) at 300K [3]. In this paper the optical absorption edge of CdS nanocrystals is measured as a function of pressure up to 10 GPa. The direct energy gap in the zb-phase increases non-linearly with pressure (quadratic) and the linear pressure coefficient is about 3.2·10
-2 eV·GPa
-1 up to 5.5 GPa. When the pressure is
raised above 6 GPa the energy gap drops suddenly by about 0.8 eV and the spectral form of the absorption coefficient is typical of semiconductors with indirect-gap transitions (Eg = 1.8 eV at 300 K). The solid-solid phase-transition from the zinc-blende to the rock-salt phase in our nanoparticles is observed at higher pressures (6 GPa) than the bulk phase-transition pressure (3 GPa). This variation of the phase-transition pressure and its dependence on the surface stabilizer can be explained by a higher value of the surface tension for the rock-salt phase nanocrystals compared to the zinc-blende one.
[1] K.J. Chang, Sverre Froyen, and Marvin L. Cohen, Phys. Rev. B, 1983, 28, 4736. [2] B. Batlogg, A. Jayaraman, J. E. Van Cleve, and R. G. Maines, Phys. Rev. B, 1983, 27, 3920. [3] M. Haase and A.P. Alisivatos, J. Phys.Chem, 1992, 96, 6756
*E-mail : [email protected] Keywords: nanocrystals, optical properties, phase transitions
221
Raman study of H2 stuffed into nano space of graphite under high pressure
A. Nakayama1, Y. Tanaka2, Y. Nishiyama3, S. Nakano4 1Center for transdisciplinary research, Niigata Univ., Niigata, Japan
2Dept. of Physics, Niigata Univ., Niigata, Japan 3Joetsu Univ. of Education, Joetsu-shi, Japan
4National Institute for Materials Science (NIMS), Tuskuba, Japan
We need some special condition to cause charge transfer interaction between carbon and H2, because the magnitude of electron affinity for carbon is equivalent to that for H2. In addition, H2 is a very stable molecule having large ionization energy. Pressure is one of the effective tools to causes unstable electron state in that way. Recently we pressurized multi-walled carbon nano-tubes (MWCNTs) with H2 using a diamond anvil cell (DAC)[1]. X-ray diffraction study clarified the inner-layer C-C π bond is stretched by loading up to 0.6 GPa. The similar phenomenon was also observed in the meso-carbon micro-beads (MCMBs), which is one of the nano-graphite materials[2]. We speculate that stretching of the in-plane C-C distance under pressure is caused by the intercalation of H2 into the regulated nano space of graphite. In this study Raman spectra of H2 stuffed into the nano space of MCMBs have been measured under pressure up to 2 GPa and at room temperature. The rotational and vibration states of H2 in the MCMBs have been compared with those of pure fluid H2. The fractured MCMBs were put in a gasket hole, which was filled with high-density H2-gas compressed up to 180 MPa at room temperature. A wolfram foil was used for a gasket. A 180º back scattering geometry with an excitation wave length of an Ar
+ laser (λ=514.5 nm) was employed for
measuring of Raman spectra. The beam was focused on a spot of about 5 μm on the sample. The spectra were obtained using a microscopic Raman spectrometer with a triple polychromator. The magnitudes of slit width and resolution are 200 μm and 1.7 cm
-1,
respectively.
Figure 1 shows the pressure dependence of vibration band of H2, coming from MCMBs-H2, which is clearly different from that observed in the fluid H2 [3]. In the MCMBs-H2 system, the peak frequency of H-H vibration band shows anomalies in pressure changes at 0.6 GPa and 1.2 GPa, which are synchronized with the phenomena of G-band from MCMBs. The anomaly observed at 0.6 GPa is also observed in the pressure change in a-axis length according to the x-ray diffraction. We speculate that H2 trapped into the regulated nano-space of graphite in MCMBs occurs phase transition at the pressures.
[1] A. Nakayama, S. Numao, S. Nakano, S. Bandow, S. Iijima, Diamond and Related Materials, 2008, 17, 548-551.
[2] A. Nakayama, S. Nakano, K. Takemura, M. Ishihara, Y. Koga, Abstracts of AIRAPT-20 Conf. 2005, 375.
[3] S. K. Sharma H. K. Mao, P. M. Bell, Phys. Rev. Lett. 1980, 44, 886-888.
* E-mail : [email protected]
Figure 1. Pressure dependences of peak frequencies of H-H vibration band and G band from MCMBs-H2. Open circles indicate data of fluid H2 [3].
222
The ac impedance of single wall carbon nanotubes at high pressures
Y. Volkova1, A. Babushkin*2, E. Obraztsova3 1,2Ural State University, Ekaterinburg, Russia
3Natural Sciences Center of General Physics Institute of Russian Academy of Sciences, Moscow, Russia.
Single-wall carbon nanotubes (SWNT) produced by HiPCO method and purified by thermal oxidation in air have been studied by impedance spectroscopy. The purity of nanotubes was estimated as 99% [1]. High pressure has been generated in the diamond anvil cell (DAC) with anvils of the "rounded cone-plane" type made of synthetic carbonado-type diamonds. The impedance of SWNT has been investigated at pressures up to 50 GPa and frequency range 1-100 kHz using a FRA-1174 (Solartron Electronic Group) device. Equivalent circuit of the SWNT sample is shown in figure 1.
Results of ac measurements were analyzed and displayed in the complex impedance plane.
[1] V. Karachevtsev et al, Photoelectric and optic properties of fullerenes, 2002, 179.
E-mail : [email protected] Keywords: single wall carbon nanotubes, high pressures, impedance spectroscopy
Figure 1. Equivalent electrical circuit of SWNT sample as a resistance R and inductance L connected in series.
223
Double wall carbon nanotubes at high pressures: doping effects
E.B. Barros1, A.L. Aguiar1, A.G. Souza Filho1, C. Caillier2, D. Machon2, A. San Miguel*2 1Departamento de Física, Universidade Federal do Ceará, Fortaleza, Brasil
2Laboratoire PMCN, Université Lyon 1 et CNRS, Lyon, France
We have investigated the vibrational properties of doped double-wall carbon nanotubes (DWNTs) using high pressure resonance Raman spectroscopy. Pristine DWNTs, Br2- and H2SO4-doped DWNTs for different pressure transmitting medium (paraffin oil and NaCl) were studied up to a maximum pressure of 32 GPa. We find that in all cases, the outer tube is mechanically supported through its interaction with the inner tube, leading to higher collapse pressures than in the corresponding single wall carbon nanotubes (SWNT). Nevertheless, the onset of the outer tube collapse leads to a cascade-type collapse of the inner tube at pressures much lower than expected for a SWNT of the same diameter. These ideas could be used for the modeling of the mechanical stability of MWNT. The outer tube of the DWNT systems is modified in different ways by the combination of chemical/pressure interaction. In particular, the mechanical resistance of the DWNT system can be improved in the case of H2SO4-doping. On the other hand, the inner tube behavior under compression is almost unaffected by the presence or not of chemical doping. DWNT appear then as excellent candidate material for the engineering of nanotubes based composite materials, with a decoupled role of the inner and outer tubes: the outer tube ensuring the chemical coupling with the matrix and the inner tube acting as mechanical support for the whole system.
This work is supported by CAPES-COFECUB agreement under contract Ph 605 /08.
*E-mail : [email protected] Keywords: carbon nanotubes, Raman spectroscopy
224
Soft-extrusion-related updated bottom-up approach to bulk, nanostructured materials processing
P. Langlois*1, N. Girodon-Boulandet1, Y. Champion2 1CNRS LIMHP, Université Paris 13, Villetaneuse, France
2CNRS ICMPE, Université Paris 12, Thiais, France.
If referring to materials as benchmarks of human civilization history, starting from the Stone Age, we might be entering the Nanomaterials Age that requires innovative processing routes, presumably consistent with the bottom-up approach, to be devised for making nanomaterials into useful forms. In the case of powder metallurgy, decisive enhancements have already been achieved but a breakthrough remained to be attained in regard to full densification.
We focused yet on producing bulk, nanostructured copper whereas dealing with grain coarsening and residual porosity. Conventional, although recently adapted or enhanced, steps included the synthesis of the nanocrystalline powders by cryo-melting[1], their precompaction by cold isostatic pressing[2], and their sintering under a controlled reductive atmosphere[3]. Additional extruding and low-temperature annealing steps were subsequently introduced in order to ensure ultimate densification and stress release respectively. Interesting structure related results have been obtained either in direct terms of mechanical properties, which can be determined under tensile testing thanks to full densification, or in corollary terms of deformation mechanism[4].
The current presentation emphasizes the extrusion step. Conversely to well-known equalchannel angular extrusion (a.k.a. ECAP) where severe plastic deformation occurs, soft extrusion refers to cold hydrostatic extrusion specifically performed with both a very small cross-section reduction and a very high applied back-pressure, optimally larger than the differential pressure necessary for the billet to extrude through the die, and indeed relates, therefore, to the bottom-up approach. For instance, no significant lattice distortion has been observed afterwards. Due to the ability of reputedly brittle materials to deform when hydrostatically contained, soft extrusion, which can be operated with back-pressures up to 1.2 GPa, is suitable for a large range of materials and should prove convenient for processing products, especially those with dimensions in the centimetre range, in parts of a field where new applications are expected to develop as well as new properties keep emerging.
[1] Y. Champion, J. Bigot, Scripta Mater. 1996, 35, 517. [2] C. Langlois, M.J. Hÿtch, P. Langlois, S. Lartigue-Korinek, Y. Champion, Metall. Mater. Trans.
A 2005, 36, 3451. [3] Y. Champion, F. Bernard, N. Guigue-Millot, P. Perriat, Mat. Sci. Eng. A-Struct. 2003, 360,
258. [4] Y. Champion, C. Langlois, S. Guérin-Mailly, P. Langlois, J.-L. Bonnentien, M.J. Hÿtch,
Science, 2003, 300, 310.
*E-mail : [email protected] Keywords : Powder Metallurgy; Extrusion; Densification; Nanostructure.
225
Transport properties of strained graphene
F.M.D. Pellegrino1,2,3, G.G.N. Angilella*,1,2,3,4, R. Pucci1,4 1Dipartimento di Fisica e Astronomia, Università di Catania,
64, Via S. Sofia, I-95123 Catania, Italy 2Scuola Superiore di Catania, Università di Catania, 5/i, Via S. Nullo, I-95123 Catania, Italy
3INFN, Sez. Catania, Italy 4CNISM, Sez. Catania, Italy
The preparation in the laboratory of single layers of graphite (graphene) has stimulated a tremendous outburst of both experimental and theoretical investigation in the structural and electronic properties of this material. Graphene is characterized by a honeycomb lattice of sp
2
hybridized carbon atoms. This gives rise to a peculiar electronic spectrum, with conical dispersion at the Fermi level, around the so-called Dirac points in reciprocal space. This justifies a relativistic-like description of the quasiparticles of the system, which are equivalent to massless Dirac fermions. This in turn results in universal features in the transport properties of graphene, which have been recently the subject of intense research. Here, we shall review some theoretical aspects of electronic transport in graphene, and specifically study the dependence of the optical conductivity on disorder and uniaxial strain.
*E-mail : [email protected] Keywords: graphene, strain, optical conductivity
226
Raman studies on Li4C60 and Na4C60 polymer under high pressure
M. Yao1, V. Pischedda1, R. Débord1, T. Wågberg2, B. Sundqvist2, A. San Miguel1 1 Université de Lyon, F-69000, France; Univ. Lyon 1, Laboratoire PMCN; CNRS, UMR 5586;
F-69622 Villeurbanne Cedex 2 Department of Experimental Physics, Umeå University, SE-90187 Umeå, Sweden
The interplay between crystal structure and electronic properties in alkali metal intercalated fullerides can be advantageously tuned with pressure in particular through polymerization processes. Raman spectroscopy is a powerful tool to explore these changes [1-5]. The unique 2D polymer structures found in Li4C60 and Na4C60 at ambient conditions have attracted a lot of interest and they constitute prototype systems for the study of the relationship between the polymerization mechanism and the alkali metal -C60 molecule electronic interactions. In this work, we present the high pressure Raman studies on Li4C60 and Na4C60 polymers.
The high pressure behavior of both materials is different from that of pure C60 polymers or other A4C60 (A=alkali metal) monomers :
At pressures below 8 GPa and 15GPa for Li4C60 and Na4C60 respectively, all the Raman modes shift up with increasing pressure, differing from the observed behaviour of non-polymeric Rb4C60, in which a phase separation has been observed [4]. Above 8 GPa for Li4C60 and 15 GPa for Na4C60, the Raman modes of both materials are significantly broadened and weakened. Such changes in Raman modes have also been observed in rhombohedral 2D polymeric phase of C60 at pressure ~ 15GPa [5]. Decompressing Li4C60 and Na4C60 from 30 GPa does not lead to the recovery of the Raman spectra of the starting material. Exposure of the decompressed samples to air leads to the recovery of the C60 molecular Raman features, which is attributed to the oxidation of alkali metal in the samples and thus depolymerization. Thus, contrary to pristine C60, in which amorphization is observed from about 22 GPa, the studied Li and Na intercalated fullerenes preserve the fullerene molecule integrity up to at least 30 GPa.
Li4C60 shows an anomalous softening of all Raman modes at 7-8 GPa and it is different from that of Na4C60 or C60 at 15 GPa. This anomaly could be related to either the high pressure metallization of Li4C60 or to a further enhancement of the Li
+ - C interactions, which could
result in the partial hybridization of Li and C pz orbitals, thus changing the C60 molecule features and causing the attenuation of all Raman modes. Our recent high pressure electrical resistance measurements seem to support the former possibility as the band gap is predicted to close around 8 GPa [6].
(1) B. Sundqvist, Struct. Bonding (Berlin) 109, 85 (2004). (2) R. Poloni, D. Machon, M. V. Fernandez-Serra, S. Le Floch, S. Pascarelli, G. Montagnac, H.
Cardon, and A. San-Miguel, Phys Rev B 77, 125413 (2008) (3) R. Poloni, G. Aquilanti, P. Toulemonde, S. Pascarelli, S. Le Floch, D. Machon, D. Martinez-
Blanco, G. Morard, and A. San-Miguel, Phys Rev B 77, 205433 (2008) (4) MG Yao, B Sundqvist, T Wågberg, Phys Rev B 79, 081403(R) (2009) (5) K. P. Meletov, J. Arvanitidis, G. A. Kourouklis, K. Prassides, and Y. Iwasa, Chem. Phys. Lett.
357, 307 (2002) (6) MG Yao, T Wågberg, B Sundqvist, to be submitted.
227
Simple systems and metals
Lectures Metal-to-semiconductor transition in lithium above 80 GPa _____________________ 229
Structural phase transitions of sodium nitride Na3N at high pressure ______________ 230
High pressure experiments as a test of Density Functional Theory _________________ 231
Boron Behavior at High Pressure ____________________________________________ 232
Posters SM 01 : Features of the ω-phase formation in zirconium and its alloys under
quasihydrostatic pressure and dynamic loading ________________________ 233
SM 02 : Phase transitions in alkali azides at pressures up to 150 GPa. ______________ 234
SM 03 : High pressure thermal conductivity of indium __________________________ 235
SM 04 : Compression of B12As2 and B12P2 single crystals beyond 100 GPa: a
Raman study _____________________________________________________ 236
228
229
Metal-to-semiconductor transition in lithium above 80 GPa
T. Matsuoka1,2, S. Onoda2, M. Kaneshige2, Y. Nakamoto2, K. Shimizu2, T. Kagayama2, Y. Ohishi1
1JASRI/SPring-8, Kouto, Sayo, Hyogo 679-5148, Japan 2KYOKUGEN, Osaka University, Toyonaka, Osaka 560-8531, Japan
Lithium (Li) is a typical and ‘simple’ metallic element at ambient pressure and nearly-free electron model is a good approximation to describe its electronic state. However, Li shows significant deviation from nearly free-electron model under high pressures. It has been theoretically predicted that the crystal structure transforms from symmetric and compact structure to lower-coordinated and complex structures, and then form pairs of atoms accompanied with the transition to an insulator near 100 GPa[1]. X-ray diffraction and Raman scattering measurements have observed the structural transitions to broken symmetry phases above near 40 GPa[2,3]. Electrical resistance measurements have reported the significant increase of the electrical resistance with applied pressure[4-6]. The superconducting transition temperature (Tc) is strongly enhanced by pressure from 0.4 mK at ambient pressure to 20 K 40 GPa[5,6]. However, the metal-insulator transition and the paired atom phase have been remained unanswered.
We have performed the simultaneous measurements of electrical resistance and X-ray diffraction (XRD) on Li at high-pressures and low-temperatures. This simultaneous study made it possible to obtain clearly the relationship between crystal structure and electrical state. Experiments were performed in SPring-8 BL10XU. The structural transitions fcc → hR1 → cI16 near 40 GPa [3] and transitions to two higher pressure phases named Li-VII and Li-VII were observed above 70 GPa. The electrical resistivity continuously increased with increasing pressure, and showed significant increase above near 80 GPa accompanied with the transition to Li-VII phase. The slope of resistance vs. temperature curves were observed to change from positive to negative in Li-VII phase. Thus, the direct evidence of pressure induced metal-to-semiconductor transition in dense Li was provided by this study.
[1] J. B. Neaton & N. W. Ashcroft, Nature 400, 141(1999). [2] M. Hanfland, K. Syassen, N. E. Christensen and D. L. Novikov, Nature 408, 174 (2000). [3] A. F. Goncharov, V. V. Struzhkin, H. K. Mao & R. J. Hemley, Phys. Rev. B 74, 184114 (2005). [4] R. A. Stager & H. G. Drickamer, Phys. Rev. 132, 124 (1963). [5] T. H. Lin & K. Dunn, J. Phys. Rev. B 33, 807 (1986). [6] V. E. Fortov, V. V. Yakushev, K. L. Kagan, I. V. Lomonosov, V. I. Postnov, and T. I. Yakusheva,
JETP Lett. 70, 628 (1999). [7] M. Bastea & S. Bastea, Phys. Rev. B 65, 193104 (2002). [8] J. Tuoriniemi, K. Juntunen-Nurmilaukas, J. Uusvuori, E. Pentti, A. Salmela and
AlexanderSebedash, Nature 447, 187 (2007). [9] K. Shimizu, H. Ishikawa, D. Takao and T. Yagi, Nature 419, 597 (2002).
*E-mail : [email protected] Keywords alkali metals, metal-to-semiconductor transition, superconductivity
230
Structural phase transitions of sodium nitride Na3N at high pressure
G.V. Vajenine1,2, X. Wang 1, I. Efthimiopoulos 1, S. Karmakar 1, K. Syassen1*, M. Hanfland3
1Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany 2Institut Anorganische Chemie, Universität Stuttgart, D-70569 Stuttgart, Germany
3European Synchrotron Radiation Facility (ESRF), F-38043 Grenoble, France
Nitrides of the heavier alkalis Na to Cs have been rather elusive, with only lithium forming a stable binary nitride Li3N. Recently, and following up on earlier preparations of thin films, a practical route to produce bulk amounts of sodium nitride Na3N was developed [1], We have investigated the structural evolution of Na3N as a function of pressure at room temperature by angle-dispersive powder x-ray diffraction in a diamond-anvil cell up to 36~GPa. The rather open cubic anti-ReO3-type structure stable at ambient pressure is followed by a series of four high-pressure modifications. Along the route, the coordination number for the nitride anion increases from 6 in Na3N-I to 8 in hexagonal Li3N-type Na3N-II, 9 in orthorhombic anti-YF3-type Na3N-III, 11 in hexagonal Cu3P-type Na3N-IV, and finally 14 in cubic Li3Bi-type Na3N-V structures. The experimental data are compared to the results of our own and previous total energy calculations for Na3N and are discussed with regard to the structural details of the five phases and their equations of state. Differences compared to the structural behavior of Li3N under pressure [2,3] are addressed.
[1] G. V. Vajenine, Inorg. Chem. 46, 5146 (2007). [2] H. J. Beister, S. Haag, R. Kniep, K. Stroessner, K. Syassen, Angew. Chem. Int. Ed. 27, 1101
(1988). [3] A. Lazicki, B. Maddox, W. J. Evans, C.-S. Yoo, A. K. McMahan, W. E. Pickett, R. T. Scalettar,
M. Y. Hu, and P. Chow, Phys. Rev. Lett. 95, 165503 (2005).
*E-mail : [email protected]
231
High pressure experiments as a test of density functional theory
A. Dewaele1, 2*, M. Torrent1, P. Loubeyre1 and M. Mezouar3
1CEA, Bruyères-le-Châtel, 91297 Arpajon Cedex, France 2Mineral Physics Institute, SUNY, Stony Brook, NY 11794, USA
3European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France
To cite R.M. Martin *1+ “Comparison of theory and experiment is one of the touchstones of ab initio electronic structure research. Because direct comparison can be made with experiment, the equation of state (EOS) is one of the tests of the state of the theory, in particular, the approximations made to treat electron-electron interactions.”
We present here a systematic comparison, for several transition metals (Fe, Co, Ni, Cu, Zn, Mo, Ag, Ta, W, Pt, Au), of experimental and calculated EOS P(V,T=295K). The experiments are performed on a wide compression range, using the diamond anvil cell tool with helium as pressure transmitting medium. The calculations are performed in the Density Functional framework, using Plane Augmented Wave method. Different functionals which approximate electron-electron interactions have been tested. This comparison enables quantifying the predictive power of Density Functional Theory. We observe that the success of each functional is correlated with the atomic number and the filling of the d-orbitals. However, there is an excessive increase of the bulk modulus with pressure for most metals.
The successes of Density Functional Theory-based techniques to predict the phase diagram of some metals will also be discussed.
[1] R. M. Martin, Electronic Structure: Basic Theory and Practical Methods, Cambridge University Press, Cambridge, 2004, p. 16.
[2] A. Dewaele, P. Loubeyre, M. Mezouar, Phys. Rev. B, 70 (9), 094112, 2004. [3] A. Dewaele, M. Torrent, P. Loubeyre and M. Mezouar, Phys. Rev. B 78, 104102, 2008
*E-mail : [email protected] Diamond anvil cell, Elemental metals, Equation of state
232
Boron behavior at high pressure
L. Dubrovinsky1, E.Yu. Zarechnaya1, N. Dubrovinskaia2,3, Y. Filinchuk4, D. Chernyshov4, V. Dmitriev4, S. van Smaalen3, V. Prakapenka5, A.S. Mikhaylushkin6,
I.A. Abrikosov6, S.I. Simak6
1Bayerisches Geoinstitut, Universität Bayreuth, 95440 Bayreuth, Germany 2Mineralphysik, Institut für Geowissenschaften, Universität Heidelberg,
69120 Heidelberg, Germany 3Lehrstuhl für Kristallographie, Physikalisches Institut, Universität Bayreuth,
95440 Bayreuth, Germany 4Swiss Norwegian Beam lines at ESRF, 38043 Gernoble, France
5GeoSoilEnviroCARS, University of Chicago, 5640 South Ellis, Chicago, IL 60637, United States
6Department of Physics, Chemistry and Biology, Linköping University, SE-581 33 Linköping, Sweden
An orthorhombic (space group Pnnm) boron phase was synthesized at pressures above 9 GPa and high temperature and it was demonstrated to be stable at least up to 30 GPa. The structure, determined by single-crystal X-ray diffraction, consists of B12 icosahedra and B2
dumbbells. The charge density distribution obtained from experimental data and ab initio calculations suggest covalent chemical bonding in this phase. Strong covalent interatomic interactions explain the low compressibility value (bulk modulus is K300=227 GPa) and high hardness of high-pressure boron (Vickers hardness HV=58 GPa), after diamond the second hardest elemental material.
* E-mail : [email protected] Keywords: boron, pressure, structure, phase relations
233
Features of the ω-phase formation in zirconium and its alloys under quasihydrostatic pressure and dynamic loading
N. I. Taluts*1, A. V. Dobromyslov1, E. A. Kozlov2 1Institute of Metal Physics, Ural Division of Russian Academy of Sciences,
Ekaterinburg, Russia 2Russian Federal Nuclear Center – Academician E. I. Zababakhin All-Russian Research
Institute of Technical Physics, Snezhinsk, Chelyabinsk region, Russia
The majority of the phase transformations occurring in materials at static pressure are observed also at dynamic (shock) loading. However, in the latter case, the duration of the applied pressure is about some microseconds. In addition, the shock-wave propagation results in high-rate plastic deformation. In this work, results of systematic structural study of features of the ω-phase (high-pressure-induced phase) formation in zirconium and its alloys under different loading conditions are presented.
The quenched Zr, Zr−Ti and Zr−Nb alloys were subjected to quasihydrostatic pressure 8 GPa and six spheres of Zr, the Zr−1 % Nb and Zr−2.5 % Nb alloys were subjected to the loading by spherical converging shock waves of different intensity. After removal of quasihydrostatic pressure, the ω-phase is retained in a metastable state and has the same morphological features as the initial α(α )-phase; namely, it has the lath or platelike morphology. Another important observation is that if the initial α(α )-phase has the platelike morphology, no transformation twins are observed within the martensite plates; the selected-area electron diffraction patterns obtained from the inner regions of the plates show the presence of ω-phase reflections of only one orientation. In addition to regions with a retained martensite structure, there are also regions in which the martensite structure is destroyed. Another characteristic microstructural feature of the ω-phase is a rather high density of stacking faults. It follows from trace analysis that these stacking faults lie on the {2 1 10} planes of the ω-phase. In electron diffraction patterns of the ω-phase, diffuse streaks linking the ω reflections are observed. These diffuse streaks correspond to sheets parallel to the (0001) planes of the ω-phase reciprocal lattice. In real space, this corresponds to linear defects, namely, the displacements of [0001]ω atomic rows. The phase and structural states of Zr and its alloys with 1 and 2.5 % Nb under loading by spherical converging stress waves depend on the loading intensity, the niobium content, and the layer depth in the sphere. The ω-phase is retained in a metastable state only after low-intensity loading, and its quantity increases with increasing content of niobium in the alloy. The areas of the ω-phase have different shapes and sizes. As in case of the ω-phase received under loading by quasihydrostatic pressure, there are two types of defects in the ω-phase structure: linear defects of displacements of [0001] atomic rows and staking faults in the planes {2 1 10} irregularly distributed on a crystal.
This study was supported by the program of the Presidium of the RAS “Thermophysics and mechanics of extreme power influences and physics of strongly compressed substance”.
*E-mail : [email protected] Keywords: pressure; shock waves; Zr and zirconium alloys; ω-phase
234
Phase transitions in alkali azides at pressures up to 150 GPa.
S. A. Medvedev*1,2, T. Palasyuk2,3, I. A. Trojan2, M. I. Eremets2, T. M. Klapötke4, J. Evers4
1Institut für Anorganische und Analytische Chemie, 55099 Mainz, Germany 2Max-Planck-Institute für Chemie, 55128 Mainz, Germany
3Institute of Physical Chemistry, Polish Academy of Sciences,01-224,Warsaw, Poland 4Ludwig-Maximilian University Munich (LMU), 81377 Munich, Germany
Metal azides have attracted considerable interest for several reasons; for example, upon being subjected to external influences (heat, irradiation, etc), they develop instability, resulting in decomposition into nitrogen and metal accompanied by burning (ignition and combustion in the case of alkali azides) or explosion (heavy metal azides). This property has resulted in the practical application of azides as a source of chemically pure nitrogen, as initial explosives, and even as photographic materials at low temperature.
From a more general viewpoint, metal azides are of interest as model systems for studying the main regularities of chemical reactions in solids with complex chemical bonding [1]. The alkali azides that possess a linear molecular anion provide a new challenge for calculations of crystal structure, lattice dynamics and electronic structure, representing the next-level model of ionic compounds beyond the extensively studied (as model systems) alkali halides. In this respect, experimental high-pressure studies of azides are believed to help in such calculations by providing a large amount of valuable data.
An important aspect of studies of azides at high pressure is the prospect of their use as a precursor in the formation of polymeric nitrogen—the ultimate example of a high energy density material [2, 3]. Recent studies have reported the transformation of sodium azide (NaN3) to a non-molecular nitrogen state with an amorphous-like structure when compressed to high pressures [4, 5]. In this respect, a comparison of the high-pressure behaviour of these substances would enable an understanding of the mechanism of pressure-induced rearrangement of azide ions and phase transitions that might result in the formation of polymeric nitrogen.
Here we present results of the Raman spectroscopy and X-ray diffraction studies of LiN3, NaN3, KN3, and CsN3 at pressures up to 150 GPa.
[1] H. D. Fair, R. F. Walker, Energetic Materials vol. 1(New York: Plenum, 1977). [2] M. I. Eremets, A. G. Gavriliuk, I. A. Trojan, D. A. Dzivenko, R. Boehler, Nat. Mater., 2004, 3,
558. [3] M. I. Eremets, R. J. Hemley, H. K. Mao, E. Gregoryanz, Nature, 2001, 411, 170. [4] M. I. Eremets, M. Y. Popov, I. A. Trojan, V. N. Denisov, R. Boehler, R. J. Hemley, J. Chem.
Phys., 2004, 120, 10618. [5] M. Popov, Phys. Lett. A, 2005, 334, 317.
*E-mail : [email protected] Keywords: azides, phase transitions
235
High pressure thermal conductivity of indium
A.A. Golyshev*, A.M. Molodets
Institute of Problem of Chemical Physics, 142432, Chernogolovka, Russia
The method of measuring electrical conductivity under shock compression is used for extracting information about thermal conductivity of indium under the high pressures and high temperatures. In this work we carried out measurements of electrical resistance of indium under shock compression, constructed the semi empirical equation of state and obtained the data on the thermal conductivity of this metal at high pressures and temperatures.
This results are shown in the Figure. The electrical resistivity of indium at multi shock compression is shown by asterisks. Numbers near the asterisks are the calculated temperatures and pressures of the shock compression. The line 2 drawn through the asterisks for clarity.
The thermal conductivity coefficient k as a function of volume at high pressures was
calculated with the use of the Wiedemann-Franz law k=LT/ were T is the temperature and L
=22.4510-8
W/K2 is the Lorenz number. These values are shown as circles in the Figure.
The theoretical curve
3/4
0
4
0
0
V
V
V
Vkk
S
S
[1]
where S=33.08 cm3/mol is shown by (1) in
the Figure. This relationship was obtained in terms of the Bloch-Gruneisen formula, according to which the electrical resistance at high temperatures is proportional to the temperature T and is inversely proportional
to the square of the Debye temperature and the Wiedemann-Franz law. According to
this relationship the thermal conductivity coefficient should not depend on the temperature
but should only be determined by the volume dependence of the Debye temperature (V).
We used the relationship
3/2
0
2
0
0
V
V
V
V
S
S
.
We should point out that the curve (1) and the experimental data (circles) on the thermal conductivity of indium were obtained independently of each other. Therefore, their agreement counts in favor of the conclusion that, in the investigated range of shock compression, the thermal conductivity of indium does not depend on temperature.
So the thermal conductivity coefficient of indium does not depend on temperature at high pressures. The threefold increase in the thermal conductivity coefficient at 27 GPa is determined only by the volume dependence of the Debye temperature in accordance with the Bloch-Gruneisen formula and the Wiedemann-Franz law.
[1] A.M. Molodets, D. V. Shakhray, A. A. Golyshev, Phys. Solid State 2009, 51, 226
*E-mail : [email protected] Keywords: thermal conductivity, indium, high pressure, shock wave
236
Compression of B12As2 and B12P2 single crystals beyond 100 GPa: a Raman study
S.V. Ovsyannikov1,2, A. Polian1, P. Munsch1, J.C. Chervin1, G. Le Marchand1 1Institut de Minéralogie et de Physique des Milieux Condensés,
Université Pierre et Marie Curie Paris 6, 140 rue de Lourmel, 75015 Paris, France 2High Pressure Group, The Institute of Metal Physics, Urals Division of the Russian Academy
of Sciences, 18 S. Kovalevskaya Str. Yekaterinburg 620041, Russia
α-Boron (B12) is a challenging material, whose rhombohedral structure remains stable at least till 100 GPa [1]. Theoretical calculation claim that its remains stable up to 270 GPa [2]. Boron-rich materials, like B12X2 (X=As, P, O) are structural prototypes of α-boron (Fig. 1). Meanwhile, B12X has an extra X-X bond between the icosahedra chains (Fig. 1), and this circumstance could probably lead to new features in dynamics of the crystal lattice under compression.
In the present work we measured non-polarized Raman spectra of B12As2 and B12P2 at pressures to and beyond 100 GPa. The experiments were carried out in a membrane diamond anvil cell [3] with beveled diamonds of culet 400/100 µm. A gasket of rhenium was used. High pressure loaded neon [4] was a pressure-transmitting medium. The Raman spectra were excited with 514.5 nm line of Ar laser and were recorded with a T64000 Jobin-Yvon triple monochromator.
The results gathered on B12As2 and B12P2 have a correspondence with a case of α--Boron, while they show
differences both in wave numbers and in their pressure coefficients. New peaks found in the Raman spectra were addressed to the vibrations of the X-X bonds. From analysis of the data we infer conclusions concerning possibilities of pressure-induced phase transitions and metallization in B12As2 and B12P2.
[1] A. Polian, J.C. Chervin, P. Munsch, M. Gauthier, J. Phys: Conf. Series 2008, 121, 042017. [2] J. Zhao, J.P. Lu, Phys. Rev. B, 2002, 66, 092101. [3] J.C. Chervin, B. Canny, J.M. Besson, Ph. Pruzan, Rev. Sci. Instrum. 1995, 66, 2595. [4] B. Couzinet, N. Dahan, G. Hamel, J.C. Chervin, High Pressure Research, 2003, 23, 409. [5] T. L. Aselage, D. R. Tallant, and D. Emin, Phys. Rev. B 1997, 56, 3122.
* E-mail : [email protected] Keywords: Boron, phase transition, pressure, Raman spectroscopy
Fig. 1. Crystal structure of (a) rhombohedral α-boron and (b) B12X2 (X=As, P, O) from Ref.[5]. The big filled circles in (b) are the X atoms.
237
Semiconductor properties
Lectures Theoretical studies of some high pressure properties of semiconductors ___________ 239
Initial structure memory of pressure-induced transformations in the phase
change memory alloy Ge2Sb2Te5 _____________________________________ 240
Pressure-induced phase transitions on amorphous covalent systems studied by a
combination of XAS and XRD and Raman spectroscopy __________________ 241
Anomalous pressure behavior of the ZnSe Raman spectrum _____________________ 242
Elastic and visco-elastic measurements in diamond anvil cell _____________________ 243
Photoluminescence of InP/GaP QDs under extreme conditions ___________________ 244
Electron-phonon coupling in semiconductors and their nanostructures: ab initio
approach. _______________________________________________________ 245
A long day’s journey in high pressure research ________________________________ 246
Posters SC 01 : High pressure structural study of the wolframite MgWO4 _________________ 247
SC 02 : Pressure dependence of the bandgap in ZnGa2Se4, CdGa2Se4, and
HgGa2Se4 ________________________________________________________ 248
SC 03 : Electrical properties of ZnS at high pressures: an impedance
spectroscopy study ________________________________________________ 249
SC 04 : Hydrostatic Raman experiments in scheelite- and wolframite-structured
divalent metal tungstates and molybdates ____________________________ 250
SC 05 : High pressure structural and spectroscopic studies of the multiferroic
spinel CdCr2S4 ____________________________________________________ 251
SC 06 : Influence effect of high pressure and magnetic field, on kinetic
coefficients and magnetic susceptibility in Cd0.94Mn0.06GeAs2 ______________ 252
SC 07 : Kinetic effects in new ferromagnetic material on the basis of Zn1-x Cdx
GeAs2 with manganese ____________________________________________ 253
SC 08 : Spin reorientation transitions in ferromagnetic semiconductors Cd1-x
MnxGeP2 and Cd1-xMnxGeAs2 induced at high pressure ___________________ 254
SC 09 : About the high pressure induced negative magneto resistance, found
out in the Cd1-xMnxGeAs2 ___________________________________________ 255
SC 10 : An influence of the hydrostatic pressure on specific resistance, Hall
coefficient, and magnetic susceptibility in p-InAs<Mn> __________________ 256
SC 11 : Investigation of polar phonons in CuMIIIO2 (MIII: Al, Ga, Sc) delafossites
by means of synchrotron FTIR spectroscopy under high pressure __________ 257
SC 12 : Electroluminescence and Band Structure in p-AlxGa1-xAs/GaAs1-yPy / n-
AlxGa1-xAs under Uniaxial Compression _______________________________ 258
SC 13 : High-pressure Raman study of zircon structure TmPO4 and observation of
a first-order phase transition ________________________________________ 259
238
SC 14 : Pressure dependence of the electronic subband structure of piezoelectric
[311] Ga0.85In0.15As/AlAs superlattices ________________________________ 260
SC 15 : Multi-phase states in the vicinity of phase transitions ____________________ 261
SC 16 : High-pressure resonance Raman spectroscopy in PbZr0.60Ti0.40O3 ____________ 262
SC 17 : Indirect carrier leakage in short-wavelength InAs/AlSb quantum cascade
lasers ___________________________________________________________ 263
SC 18 : Buried tunnel junction 2.4-μm GaSb VCSEL investigated by high
hydrostatic pressure _______________________________________________ 264
SC 19 : High Pressure Studies on II-VI Ternary Alloy Zn1-xBexSe ____________________ 265
239
Theoretical studies of some high pressure properties of semiconductors
M. L. Cohen*
Department of Physics, University of California, Berkeley, California 94720, USA, and Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720, USA
The importance of the use of pressure as a tool to study semiconductors is hard to overstate. Experimental and theoretical studies have been done on the influence of pressure on electronic and vibrational properties as well as its role in inducing structural, magnetic, and superconducting transitions. In addition to the need for extraordinary skill and ability to construct sophisticated equipment, experimentalists need excellent physical insight to choose important projects. Manuel Cardona possesses these qualities. He has picked physically important problems, developed useful methods and approaches, interpreted the resulting data, and has even infringed on the theorist’s domain by doing his own calculations. We theorists have often been in a position only to pick up the “leftovers” and to try to keep up. At times we led, but this hasn’t been easy. What is “easy” is changing the lattice parameter input for a computer program to simulate the effects of pressure. No special equipment is needed to simulate pressures over a broad range and even extraordinary pressures. However, predicting or explaining existing data often does require insight and skill. For example, generally we still can’t predict new structures from scratch. We need candidates to choose from. Despite the limitations on theory, using the insights and results from our experimental colleagues, like Manuel Cardona, and some of our own, we have been able to contribute to this field by predicting new structures, electronic properties, and superconductivity. Although my discussion will focus on some of the contributions of theoretical work, I want to acknowledge the debt we owe to our experimental colleagues and in particular to Manuel Cardona.
*E-mail : [email protected]
240
Initial structure memory of pressure-induced transformations in the phase change memory alloy Ge2Sb2Te5
C. Levelut1, M. Krbal2, J. Haines2, A.V. Kolobov2,3, R. Le Parc1, P. Fons3, M. Hanfland4, A. Pradel2, M. Ribes2 and J. Tominaga3
1LCVN, UMR 5587 CNRS-UM2, Université Montpellier II, Montpellier, France 2ICGM, UMR 5253 CNRS-UM2, Université Montpellier II, France
3CANFOR, NIAIST, 111, Higashi, Tsukuba 3058562, Japan 4European Synchrotron Radiation Facility, BP 220,38043 Grenoble, France
Quasibinary GeTe-Sb2Te3 alloys are employed in optical data storage (such as DVD-RAM) because they may undergo reversible crystalline to amorphous phase transition under the action of a laser beam. The effect of temperature on such process is usually taken to be important. However the transformation to a less dense phase (by about 6%) upon heating is also accompanied by pressure effects: amorphous bits confined into crystalline matrix cannot expand and thus the application of a laser beam results in a pressure up to few GPa. Pressure thus appears to be an important parameter to study [1,2,3]. Ge2Sb2Te5 can be amorphized, independently of temperature in the 25-145°C range under hydrostatic pressure above 10GPa [4]. The stable structure Ge2Sb2Te5 is trigonal, but the material used in devices has a metastable distorted rocksalt structure (cubic structure).
In this contribution, we compare the behavior of the cubic and hexagonal phases of Ge2Sb2Te5 under pressure. Measurements were performed at ESRF on beamline ID09A (Grenoble, France) at room temperature with l=0.4115 Å using He as pressure-transmitting medium. Our results show the existence of a memory effect linked to the initial structure with respect to the high-pressure behavior. For the cubic fcc (face centred cubic) phase, an amorphous phase starts to grow from 15 to about 25 GPa. Upon further compression a new crystalline, bcc (body centered cubic) phase appears. The compression-decompression cycle for this phase is irreversible, and an amorphous phase predominates after decompression, together with some remaining bcc phase. On the other hand the stable trigonal phase remains crystalline upon compression. First it transforms to an intermediate orthorhombic phase (GeS type) and then also to a bcc phase. Upon decompression, the bcc phase retransforms to the intermediate crystalline phase and then the original trigonal crystalline structure is restored. We interpreted this phenomenon of memory of the initial structure as being related to the presence (or absence) of vacancies. In the cubic material, the collapse of vacancies upon compression provides the possibility of very large degree of atomic displacement, giving rise to nanoscale phase separations, so that atoms "forget" their initial arrangement. Starting from the denser trigonal structure, the phase transitions are reversible due to limited atomic motion.
[1] A. V. Kolobov et al, Phys. Rev. Lett. 2006, 97, 035701. [2] A. V. Kolobov et al, Appl.Phys. Lett. 2007, 91, 021911. [3] K. S. Andrikopoulos et al, J. Phys. Chem. Solids 2007, 68, 1074-1078. [4] M. Krbal et al, Appl. Phys. Lett. 2008, 93, 031918.
*E-mail : [email protected] Keywords : x-ray diffraction under pressure, phase-trasnition, chalcogenure, DVD-Ram
241
Pressure-induced phase transitions on amorphous covalent systems studied by a combination of XAS and XRD and Raman spectroscopy
F. Coppari*1, E. Principi2, A. Congeduti3, S. Chagnot3, A. Polian1, A. Di Cicco1,2 1IMPMC-CNRS-Université P.et M.Curie, Paris VI, 140 rue de Lourmel 75015 Paris, France
2CNISM, Dipartimento di Fisica, Università di Camerino, Camerino (MC), Italy 3Soleil Synchrotron, L'Orme des Merisiers, St. Aubin 91192 Gif s/Yvette, France
The application of an external pressure on amorphous semiconductors, such as silicon (a-Si), germanium (a-Ge) and glasses (GeO2, SiO2) can result in a variety of phase transitions including polyamorphism [1,2,3,4 and ref. therein]. Besides several measurements have been carried out, results are often contradictory. In order to obtain consistent data concerning amorphous-amorphous transitions it is important to perform different measurements in the same pressure conditions and on the same sample. In our work we present the results of combined high-pressure Raman spectroscopy and X-ray absorption/diffraction (XAS/XRD) measurements using diamond anvil cells. XAS and XRD measurements where performed in the new energy dispersive ODE beamline at Soleil Synchrotron, where the existent setup was upgraded in order to collect absorption spectra and diffraction patterns at the same time and on the same sample. The combination of these techniques permits an accurate characterization of the system under investigation, highlighting the occurrence of transitions to crystalline structures. Additional information about the phonon vibrations and the occurrence of phase transitions are obtained by Raman scattering. This approach allowed us to find interesting results on the behavior of a-Ge [4,5] under pressure. Depending on the density of defects characterizing the sample, a-Ge is seen to undergo a transition to a metallic phase around 8 GPa still remaining amorphous and to a crystalline metastable structure (ST12-Ge) around 7 GPa upon depressurization (for low density of defects). The same methodological approach has been applied to an amorphous SiGe alloy, for which high-pressure data are not yet available in literature.
[1] A. Hedler et al., Nature Materials 2004, 3, 804 [2] P.F. McMillan et al., Nature Materials 2005, 4, 680 [3] M. H. Bath et al., Nature 2007, 448, 787 [4] A. Di Cicco et al., Phys. Rev. B 2008, 78, 033309 [5] F. Coppari, et al., submitted Phys. Rev. B on February 2009
*E-mail : [email protected] Keywords: high-pressure, polyamorphism, amorphous, semiconductors
242
Anomalous pressure behavior of the ZnSe Raman spectrum
R. E. Tallman1, B. A. Weinstein*1, B. Shih1, P. Zhang1, R. Lauck2, M. Cardona2 1SUNY at Buffalo, Department of Physics, Buffalo, NY, USA
2Max Planck Institut fur Festkorperforschung, Stuttgart, Germany
Experimental studies of the effects of hydrostatic pressure on the one- and two- phonon Raman spectra of ZnSe show a striking anomaly compared to ZnS, ZnTe and many other semiconductors. Diamond-anvil cell measurements performed on vapor-grown
68Zn
76Se
crystals[1] and natural composition ZnSe crystals[2] for pressures up to the structural transition at 13.7 GPa (visual PT) show a 20-fold broadening of the TO(Γ) peak (to ~ 60cm
-1
FWHM) in a range 2 – 3 GPa below the transition. This effect is found at room temperature, but not in pressure measurements at 11 K (He-medium). See Figures 1 and 2 below. It differs markedly from what is observed in ZnS, GaP, and several other materials, where broadening of the optical phonon Raman peaks by factors of 2-5 arises from multi-phonon resonant anharmonic interactions. This mechanism is unlikely in ZnSe, since its TO(Γ) frequency lies inside a twophonon density-of- states gap at all observation pressures. We attribute the anomalous TO(Γ) broadening in ZnSe to a break-down of the q = 0 selection rule associated with local domain formation antecedent to the phase transition. Note in Fig. 1, however, that the sharpness of the LO(Γ) peak and (to some extent) of the 2TA critical-point features persists. Hence, the localization and loss of q-conservation is not as severe as in amorphous materials, but may instead reflect nanometer domains. Calculations of the TO(Γ) line-shape for localization in zincblende and wurtzite nanodomains are explored to test these ideas. Resonance Raman effects (e.g., in the LO(Γ) peak) and anharmonic mixing of modes that become allowed in confined geometry may enhance the localization-induced broadening. When approaching the transition pressure, domains can arise, e.g., by formation of stacking faults between zincblende and wurtzite regions, or by similar processes favorable in systems having close total-energy polytypes. It appears that ZnSe is particularly susceptible to such processes.
[1] R. E. Tallman, Ph.D. dissertation, 2009. [2] B. A. Weinstein, in High Pressure Science and Technology, 1979, Vol. 1, ed. by K.
Timmerhaus and M. S. Barber, (Plenum, NY,) p.141.
*E-mail : [email protected] ZnSe, Raman, pressure, nanodomains
243
Elastic and visco-elastic measurements in diamond anvil cell
F. Decremps1, L. Belliard2, B. Perrin2 and M. Gauthier1 1IMPMC, UPMC – CNRS, Paris, France
2INSP, UPMC-CNRS, Paris, France
Major progress on ultrafast acoustics instrumentation and diamond anvils design during the last two years now allows detailed elastic and visco-elastic studies under extreme conditions and on a wide variety of systems. I will here mainly review the state of the art of the recent development of a method combining the time-resolved picosecond optical technique and a diamond anvil cell to measure sound velocity
[1]. Contrary to other groups which currently
scope with these problems mostly using large facilities, we propose here entirely new and novel technique to measure the sound velocity of solid and liquid under high pressure and high temperatures. I will illustrate these possibilities by a number of recent studies on crystalline, amorphous, polycrystalline and liquid metals or semiconductors. Prospects will be discussed.
[1] F. Decremps, L. Belliard, B. Perrin and M. Gauthier, Phys. Rev. Lett. 2008, 100, 3550.
*E-mail : [email protected] Keywords : Elasticity, equation of state, picoseconds acoustics
244
Photoluminescence of InP/GaP QDs under extreme conditions
M. Millot1,*, C.V. Dewitz2, F. Hatami2, W.T Masselink2, J. González3,4, J. M. Broto1 1Laboratoire National des Champs Magnétiques Intenses (LNCMI )-CNRS-UPR3228,
Université de Toulouse, 143 avenue de Rangueil,31400 Toulouse, France 2Humboldt Univ, Dept Phys, D-12489 Berlin, Germany
3MALTA Consolider Team, DCITIMAC, Facultad de Ciencias, Universidad de Cantabria, Santander, Spain
4Centro de Semiconductores, Facultad de Ciencias, Universidad de los Andes, Merida, Venezuela
The combination of high magnetic field with high hydrostatic pressure gives a powerful tool to explore electronic properties of solids. While pressure tunes structural parameters and possibly induces structural and electronic phase transitions, high magnetic fields enable to probe the electronic structure in great details. Taking advantage of a novel Diamond Anvil Cell (DAC) suitable for optical measurements under pulsed magnetic fields up to 55 T [2] we have performed magneto-photoluminescence (PL) ) on InP/GaP quantum dots (QDs) between 4 K and 200 K and up to 2 GPa.
Whereas InGaAs/GaAs self-assembled QDs have been extensively investigated InP/GaP QDs has been given much less attention. This system deserves a strong interest, however, for both (i) a fundamental understanding of the exciton physics of QDs based on direct-indirect bandgap semiconductors, as well as (ii) its potential applications to visible light emitters [1].
High pressure yields a shifting of energy levels and shed light on the band-alignment by tuning the interfacial strain in this system owing to different lattice parameters and bulk modulus for matrix and dot compounds.
Besides, magnetic behavior unveils the nature of the discrete energy levels and gives access to reduced effective mass and confinement energy as well as angular momentum. A Γ-X crossover in the dots and a type I to type II transition at 1.5 GPa are further evidenced by additional high-pressure optical absorption measurements at room temperature.
[1] A. Ugur, F. Hatami, and W. T. Masselink, A. N. Vamivakas, L. Lombez, and M. Atatüre, Appl. Phys. Lett. 93 (14), 2008.
[2] M. Millot, J.-M. Broto, and J. González, Phys. Rev. B 2008, 78, 155125.
*E-mail : [email protected] Keywords: pressure sensors; photoluminescence; high magnetic field
245
Electron-phonon coupling in semiconductors and their nanostructures: ab initio approach.
J. Sjakste1*, N. Vast1, V. Tyuterev1,2 1Ecole Polytechnique, Laboratoire des Solides Irradiés, CEA-DSM, CNRS,
91128 Palaiseau, France 2Tomsk State Pedagogical University, Tomsk, Russia
Interaction of excited electrons with phonons plays a central role for electronic and transport properties at the nanoscale. It is the dominant process limiting the excitation lifetime of electrons at medium excitation energies. Under stress, the relative positions of the electronic levels change, thus allowing or forbidding electronic transitions which involve interactions with different phonons .Experimental techniques involving pressure studies are thus well suited for exploring electron-phonon coupling in semiconductors
[1-3].
Recently, we developed a fully ab initio theoretical approach which permits to calculate the electron-phonon constants and scattering times for collisions of carriers in the conduction band with short-wavelength phonons
[4,5]. This approach enabled us to describe the relaxation
of hot electrons in GaAs, and to calculate the lifetime of the direct exciton in GaP[4,5]
, all in excellent agreement with experiments. We also described the evolution of the lifetime of the direct exciton in GaAs under pressure
[6], which is determined by the electron-phonon
scattering rate. This study permitted us to explain the experimental results of work[1]
.
After presenting our results GaAs under pressure and on GaP, we will present our new work on interaction of excited electrons with short-wavelength phonons in Si. Si is an indirect band gap semiconductor, with conduction band minima near X point, and thus the scattering of electrons by phonons from one equivalent X valley to another one plays an important role in determining the electronic mobility. Moreover, the same electron-phonon scattering process plays an important role in interaction between shallow impurity levels in Si
[3]. Finally, we will
discuss the effects of nanostructuring on the electron-phonon coupling constants. In all of today's works on nanostructured materials, bulk values of electron-phonon coupling constants are used
[2]. However, our results for the GaAs/AlAs superlattices show that
electron-phonon coupling constants in layered materials are widely different from the bulk ones.
[1] A. R. Goni, A. Catarero, K. Syassen, M. Cardona, Phys. Rev. B 41, 10111 (1990). [2] S. Guha et al, Phys. Rev. B 58, 7222 (1998). [3] R. Kh. Zhurkavin et al, Appl. Phys. Lett. 90, 051101 (2007). [4] J. Sjakste, N. Vast, V. Tyuterev, Phys. Rev. Lett. 99, 236405 (2007). [5] J. Sjakste, V. Tyuterev, N. Vast, Appl. Phys. A 86 (2007) 301. [6] J. Sjakste, V. Tyuterev, N. Vast, Phys. Rev. B 74, 235216 (2006).
*E-mail : [email protected] Keywords: electronic relaxation, vibrational properties, intervalley scattering
246
A long day’s journey in high pressure research
M. Cardona*
Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany
My first contact with high pressure physics was in the Fall of 1956. I had arrived to Harvard from Spain and was lucky to join William Paul’s group as a graduate student. Bill had arrived from Scotland in 1952 with a project involving the dependence of the gaps of the Pb chalcogenides on pressure using P.W. Bridgman’s equipment and expertise. But alas! Bridgman was just about to retire and Bill was asked to take over his equipment and decided to use it for the investigation of the then more topical diamond and zincblende-like semiconductors. Bridgman (whom I had the fortune to meet) left behind basically only his high pressure equipment. Bill was able to acquire some optical and other ancillary equipment (Sputnik helped!) and quickly built up his own group which I was allowed to join. I soon was able to measure the pressure dependence of the dielectric constant of germanium and silicon, in particular the then unexpected fact that it decreases with pressure. I also measured the pressure dependence of the direct edge of germanium. I hardly suspected at the time that I would be involved in high pressure physics till well after my retirement 10 years ago. I have published over 210 papers with the words “pressure”, “stress” or “strain” in their title. By themselves, they would give me an h-index of 38. The two most cited among them deal with the effect of pressure on phonons [1,2]. When published, these papers were only of academic interest. Emphasis on superlattices and nanostructures catapulted them into the center of the solid state literature. According to the number of citations, two papers followed on the effect of strain on excitonic transitions [3,4]. During the past 10 years of retirement I have published 20 articles on pressure effects in semiconductors, the most recent one dealing with strain induced spin splittings [5]. The talk will summarize half a century of work in the field and bring to the fore the many collaborators and countries who have helped me in this endeavor. They deserve my warmest recognition and thanks.
[1] F. Cerdeira et al., Phys. Rev.,B 5, 580 (1972), cited 535 times [2] E.Anastassakis et al., Solid State Commun., 8, 133 (1970), cited 330 times [3] L.D. Laude et al., Phys. Rev. B 3, 2623 (1971), cited 179 times [4] B. Welber et al., Phys. Rev. B 12, 5729 (1975), cited 170 times [5] A.N. Chantis et al., Phys. Rev. B78, 075208 (2008)
*E-mail : [email protected]
247
High pressure structural study of the wolframite MgWO4
J. Ruiz-Fuertes1,2,*, S. López5, D. Errandonea1,3, R. Lacomba-Perales1,2, A. Segura1,2, A.H. Romero5, P. Rodríguez-Hernández1,4, and A. Muñoz1,4
1Malta Consolider Team 2Departamento de Física Aplicada-ICMUV
3Fundación General de la Universidad de Valencia, Spain 4Departamento de Física Fundamental II, Universidad de La Laguna, Tenerife, Spain
5CINVESTAV, 76230 Querétaro, México.
MgWO4 is one of the most extensively studied metal tungstates mainly due to its interest as a useful scintillator material for cryogenic applications used in search for rare events in particle physics[1]. In general, metal tungstates crystallize in the scheelite, wolframite, or related structures depending mostly on the metal cation accompanying the tungsten. In our case MgWO4 adopts a monoclinic wolframite structure (P2/c) where the MgO6 and the WO6 octahedral units share edges. Even though there is one work reporting the structural properties of this material under pressure[2], it was limited to 8 GPa and no phase transition was detected. Aiming to extend the structural study of this compound towards higher pressures we have performed synchrotron x-ray diffraction experiments in a DAC and ab initio calculations up to 50 GPa. Experiments were performed at the I15 beamline of the Diamond Light Source. We found the onset of a phase transition around 21 GPa, coexisting the low- and highpressure phases up to 41 GPa. Interestingly, the monoclinic b angle of the wolframite phase is reduced upon compression pointing toward a symmetry increase of the structure up to the transition onset. From our studies we determined a third-order Birch-Murnaghan EOS with parameters, V0 = 131 Å
3, B0 = 165 GPa and B'0 = 4. We also established the pressure
evolution of the W–O and Mg–O distances and found that in the low-pressure phase the W–O octahedra basically behave as rigid units and that the Mg–O octahedral account for most of the crystal compressibility. In addition, the selective octahedral compressibility explains the non-isotropic behaviour found in MgWO4. An attempt to solve the structure of the new phase is made from the analysis of the experimental data and the theoretical calculations. A triclinic structure similar to that of CuWO4 (P 1 ) is proposed for the high-pressure phase of MgWO4.
[1] V. B. Mikhailik, H. Kraus, et al. J. Phys.: Condens. Matter 20, 365219 (2008) [2] J. Macavei and H. Schulz. Zeitschrift für Kristallographie 207, 193 - 208 (1993)
*E-mail : [email protected]
248
Pressure dependence of the bandgap in ZnGa2Se4, CdGa2Se4, and HgGa2Se4
O. Gomis1*, F.J. Manjón1, D. Errandonea2, J. Ruiz-Fuertes2, E. Pérez-González3, A. Muñoz3, P. Rodríguez-Hernández3, M. Fuentes-Cabrera4, I.M. Tiginyanu5,
V.V. Ursaki5 1MALTA Consolider Team - Departamento de Física Aplicada,
Universidad Politécnica de Valencia, 46022 Valencia, Spain 2MALTA Consolider Team - Departamento de Física Aplicada - ICMUV,
Universidad de Valencia, 46100 Valencia, Spain 3MALTA Consolider Team - Departamento de Física Fundamental II
Universidad de La Laguna, La Laguna, Tenerife, Spain 4Center for Nanophase Materials Sciences, Oak Ridge National Laboratory,
Oak Ridge, P. O. Box 2008, TN 37831-6494, USA 5Institute of Applied Physics, Academy of Sciences of Moldova, 2028 Chisinau, Moldova
ZnGa2Se4, CdGa2Se4 and HgGa2Se4 are ordered-vacancy semiconductors of the AIIB2
IIIX4
VI
family that crystallize in two different structures. CdGa2Se4 and HgGa2Se4 crystallize in the
defect chalcopyrite structure (I 4 ) [1], whereas ZnGa2Se4 crystallizes in the defect stannite
structure (I 4 2m) [2]. These semiconductors exhibit similar non-linear pressure dependences of their optical bandgaps despite their different structures. They show similar small positive pressure coefficients at low pressures and small negative pressure coefficients above 10 GPa. The main difference is that, above 10 GPa, CdGa2Se4 and HgGa2Se4 show a direct-to-direct bandgap crossover while ZnGa2Se4 shows a direct-to-indirect bandgap crossover. These results are in good agreement with ab initio calculations [3]. Finally, after decompression of the samples from the disordered rocksalt phase occurring in these compounds above 14 GPa the samples undergo a phase transition towards a disordered zincblende structure with a much smaller direct bandgap and pressure coefficient than that observed in the defect chalcopyrite and stannite structures.
[1] A. Grzechnik, V.V. Ursaki, K. Syassen, I. Loa, I.M. Tiginyanu, and M. Handfland, J. Solid State Chem. 160, 205 (2001).
[2] T. Hanada, F. Izumi, Y. Nakamura, O. Nittono, Q. Huang, and A. Santoro, Physica B 241, 373 (1998).
[3] M. Fuentes-Cabrera, J. Phys.: Condensed Matter 13, 10117 (2001).
*E-mail : [email protected] Keywords: ordered-vacancy semiconductors, chalcopyrites, optical absorption
249
Electrical properties of ZnS at high pressures: an impedance spectroscopy study
Y. A. Kandrina*, A. N. Babushkin
Ural State University, Ekaterinburg, Russia
It is known, that in ZnS there is a transition at pressure 16 GPa. The sharp reduction of electrical resistance has given the basis to consider this transition as transition "semiconductor - metal". On pressure dependence of resistance there is a maximum at pressure about 41 GPa. At pressures 41-47 GPa the dependences of resistance, thermo-emf and energy of activation of conductivity have the features connected to reorganization of electronic structure. After the pressure treatments ZnS is irreversible changes the electrical characteristics.
The purpose of our work was to study the electrical properties of ZnS by impedance spectroscopy at pressures 20-50 GPa.
High pressure has been generated in the diamond anvil cell (DAC) with anvils of the "rounded cone-plane" (Verechagin-Yakovlev) type made of synthetic carbonado-type diamonds. These anvils are good conductors and allow measure the electrical properties of the sample placed in the DAC.
From measurements on a direct current it is known [1] that at pressures 41-47 GPa resistance and thermo-emf have the maximum, and the energy of activation of conductivity sharply grows. At the same pressures the character of temperature dependence of resistance changes. The features of the pressure dependences of resistance, thermo-emf and energy of activation of conductivity at pressure 41-47 GPa are connected, apparently, to the reorganization of electronic spectrum of ZnS.
According an ac measurements the occurrence in the equivalent circuit of a sample of a constant phase element testifies that in ZnS at pressures about 40 GPa there are connected charges (polarization) giving in hodograph of the impedance the shift of phases between a current and voltage, characteristic for inductance.
At pressures 37-40 GPa the connected charge have occurred in ZnS. This rang of pressures corresponds to pressures, where at a dc measurements the features of pressure dependences of resistance are observed.
Probably, at pressure about 40 GPa in ZnS the reorganization of crystal structure resulting in occurrence in a sample a mixtures of phases and an internal electrical field are begins.
The most change of a constant phase element is observed at ~40-42 GPa. At these pressures there is a known phase transformation. These effects can be connected with change of internal electrical polarization counteracted to movement of carriers of a charge.
[1] A.N. Babushkin, State Physics. 1992, 34, 1647.
*E-mail : [email protected] Keywords (high pressure, impedance spectroscopy, ZnS)
250
Hydrostatic Raman experiments in scheelite- and wolframite-structured divalent metal tungstates and molybdates
R. Lacomba-Perales1,2,*, D. Errandonea1,3, D. Martínez-García1,2, J. C. Chervin4, A. Polian4
1Malta Consolider Team 2Departamento de Física Aplicada-ICMUV
3Fundación General de la Universidad de Valencia (Spain) 4IMPMC, Université P.M. Curie, Paris (France)
We performed RT Raman measurements in single crystals of divalent metal tungstates and molybdates up to 45 GPa. The experiments were performed in a DAC using neon as pressure transmitting medium. The studied compounds crystallize either in the tetragonal scheelite structure (I41/a) (CaWO4, SrWO4, SrMoO4, BaWO4 and PbWO4) or in the monoclinic wolframite structure (P2/c) (ZnWO4 and CdWO4). We have extended previous experimental studies of this family of materials from pressures near 20 GPa to 45 GPa and performed our experiments under quasi-hydrostatic conditions. For CaWO4 and SrWO4 we found a phase transition at 11.0 GPa and 14.5 GPa respectively, to the monoclinic M-fergusonite structure (I2/a). This phase remains up to 35 GPa in the case of CaWO4. At higher pressure all the peaks disappear and broad bands appear in the spectra, sign of a possible amorphization. In contrast, for SrWO4 the M-fergusonite exists up to 19.7 GPa. Beyond this pressure new peaks appear in the Raman spectra; additional changes take place at 40.7 GPa. The behaviour of the scheelite SrMoO4 is similar to that of SrWO4. For the scheelites BaWO4 and PbWO4 a dramatic change is observed at 7 GPa and 6 GPa, respectively. The new spectra correspond to the monoclinic BaWO4-II and PbWO4-III phases (P21/n), which we have found to remain stable up to 45 GPa. In the case of the wolframites, ZnWO4 and CdWO4 very similar final spectra are observed above 31 GPa and 35.8 GPa, respectively. This fact can be explained assuming a
phase transition to the monoclinic -fergusonite structure (C2/c). In ZnWO4 the transition
from wolframite to -fergusonite is direct, whereas in CdWO4 an intermediate phase is observed from 21.2 to 35.8 GPa. In all the studied samples the induced structural changes are reversible upon decompression. Another important fact is that we did not find any evidence of a possible decomposition of the studied tungstates into component oxides. To conclude we will compare the differences and similarities of our results with those obtained under non-hydrostatic conditions.
*E-mail : [email protected]
251
High pressure structural and spectroscopic studies of the multiferroic spinel CdCr2S4
I. Efthimiopoulos1*, S. Karmakar1, X. Wang1, K. Syassen1, P. Lemmens2, V. Tsurkan3, M. Hanfland4 and Y.-L. Mathis5
1Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany 2Inst. For Condensed Matter Physics, TU Braunschweig, D-38106 Braunschweig, Germany 3Inst. of Applied Physics, Academy of Sciences of Moldova, MD-2028 Chisinau, R. Moldova
4European Synchrotron Radiation Facility (ESRF), F-38043 Grenoble, France 5Forschungszentrum Karlsruhe GmbH, Institut für Synchrotronstrahlung (ISS),
D-76344 Eggenstein, Germany
The behavior of spinels under non-ambient conditions has been the subject of extensive investigations, since the spinel structure and its high-pressure modifications play an important role in modelling major mineral phases of the upper mantle [1]. Within condensed matter physics, several spinels have recently attracted considerable interest because of the intimate interplay of structural, magnetic and ferroelectric properties. One of the most recent
examples is the cubic CdCr2S4 spinel compound (SG Fd3 m), which was reported to exhibit relaxor ferroelectric behavior, displaying a particularly large magneto-capacitive effect at ~130 K [3]. In addition, CdCr2S4 becomes ferromagnetic at TCurie=85 K [3]. Clear evidence for a strong coupling between lattice, electrical polarization and magnetism comes from temperature dependent studies of infrared- and Raman-active phonon modes of CdCr2S4 and similar chalcogenides [2]. This raises the question on how the tuning of elasticity by pressure affects its physical properties.
Here we report the results of our high pressure (HP) investigations of CdCr2S4. We have performed Raman spectroscopy, synchrotron-based infrared (IR) reflectance measurements, and x-ray diffraction experiments at room temperature. Overall, three structural phase transitions are clearly resolved: at ~13 GPa the cubic structure adopts a tetragonal phase, at ~23 GPa an orthorhombic distortion occurs, while at ~39 GPa amorphization takes place. The amorphous phase persists after full decompression. Our HP IR study reveals that the structural transitions are accompanied by changes in the electronic properties. In particular, at ~12 GPa, a reversible insulator-to-metal transition occurs. The findings are compared with the pressureinduced behavior of other spinel compounds. The interplay between structure and multiferrocity will also be discussed within a thermodynamic framework.
[1] D. Levy et al., Phys. Chem. Miner. 2004, 31, 122 and references therein. [2] T. Rudolf et al., Phys. Rev. B 2007, 76, 174307 and references therein. [3] J. Hemberger et al., Nature 2005, 434, 364.
*E-mail : [email protected]
252
Influence effect of high pressure and magnetic field, on kinetic coefficients and magnetic susceptibility in Cd0.94Mn0.06GeAs2
A.Y. Mollaev1*, I.K. Kamilov1, R.K. Arslanov1, T.R. Arslanov1, U.Z. Zalibekov1, V.M. Novotorzev2, S.F. Marenkin2
1Institute of Physics, Daghestan Scientific Center of the Russian Academy of Sciences, 367003, Makhachkala, Russian
2Institute of common and inorganic chemistry of the Russian Academy of Sciences, Moscow, Russian
There was carried out a complex study of high temperature ferromagnetic semiconductor Cd0.94Mn0.06GeAs2. There was measured: specific resistivity ρ, temperature dependencies of specific resistivity ρ(T) and Hall coefficient RH(T) and magnetic susceptibility at high hydrostatic pressure up to 9 GPa at rise and fall of pressure according to methods *1,2+. Let’s consider baric dependence of specific resistivity ar pressure rise. Specific resistivity up to P=4.7 GPa changes very weakly, then at P=4.7 GPa starts phase transition (PT) suddenly falls for two order and at P=6.1 GPa phase transition ends ρ0/ρH=12, ςH =12.3 Ω
-1 cm
-1, ρ0=ρ0 . Phase
transition (PT) is also observed at fall of pressure at P=2.7 GPa on curve ρ(T). Dependence of Hall coefficient from pressure is the same. Hall coefficient in PT region falls for 3 orders. Concentration of carriers in saturation region is ≈10
18 cm
-3 RH0=RH0 .Thus according to values of
specific resistivity and Hall coefficient before and after PT one may conclude that in p- Cd0.94Mn0.06GeAs2 takes place reversible structural PT semiconductor – semiconductor. Temperature dependences ρ(T) and RH(T) have semiconductive character with activation energy ρ∼Ea/kT (Ea =0.1 eV). For the first time there was found on baric dependence (χ/χ0)(P) a magnetic spin reorientation PT ferromagnetic – antiferromagnetic (FM–AFM) at pressure P=2 GPa; the pressure of susceptibility shoulder at P> GPa terrifies it. Temperature dependence (χ/χ0)(P) T=295–340 K shows, that maximum (χ/χ0)(P) moves to lower pressure with temperature increase, the amplitude of PT FM–AFM falls. It is know that experimental studied Hall coefficient in ferromagnetic semiconductor comprises of normal and anomalous Hall coefficients are calculated by interactive graphic constructions of magnetic field dependences of Hall resistance. A negative magnetic resistance induced by high pressure was found on baric dependences (Δρxx/ρ0)(P) and (Δρzz/ρ0)(P). A considerable contribution into magnetic resistance may give scattering of circuit carriers up to P<1 GPa on fluctuations of magnetic resistance is positive. There takes place a regulation of spin ions of manganese with rise of pressure and magnetic field, what lower the scattering and leads to negative magnetic resistance: magnetic PT FM–AFM observed at P=2 GPa testifies it, and it takes place in the region of transition of magnetic resistance from positive to negative.
[1] L. G. Khvostantsev, L. P. Vereshagin, A. P. Novikov, High Temp.-High Pressure 1977, 9, 6, 637.
[2] A. Yu. Mollaev, R. K. Arslanov, L. A. Saypulayeva, S. F. Marenkin, Inorganic materials 2001, 37, 4, 405.
* E-mail : [email protected] Keywords: Hall coefficients, high pressure, magnetic field
253
Kinetic effects in new ferromagnetic material on the basis of Zn1-xCdxGeAs2 with manganese
A.Y. Mollaev1*, L.A. Saypulaeva1, A.G. Alibekov1, A.A. Abdullaev1, S.F. Marenkin2
1Institute of Physics, Daghestan Scientific Center of the Russian Academy of Sciences, 367003, Makhachkala, Russian
2Institute of common and inorganic chemistry of the Russian Academy of Sciences, Moscow, Russian
Temperature dependencies of electroconductivity have been studied in the 77-300 K range for a new high temperature ferromagnetic semiconductor p-Zn1-xCdxGeAs2:Mn. Baric dependencies of specific resistivity ρ(Р) and Hall coefficient RH(Р) have been measured in the region of room temperatures. Method and technique of experiment is described in detail in [1, 2]. Studied crystals were synthesized from highly pure powders of CdAs2, ZnAs2 and Ge, prepared from single crystals. Parameters of studied samples p-Zn1-xCdxGeAs2 with various content of manganese are given in table 1. Samples №1-3 doped by Mn are ferromagnetics.
Table №1 Characteristics of studied samples p- Zn0.9Cd0.1GeAs2 with various content of manganese
№ sample Х Type of the conductivity
ρ, Ω cm Concentration of main carriers, cm-3 at 300 К
1 0.06 р 0.0152 1.9 1020 2 0.1 р 0.0125 1.1 1020 3 0.14 р 0.114 1.3 1020
Specific resistivity increases linearly with pressure for p-Zn0.9Cd0.1 Mn0.06GeAs2 №1, p-Zn0.9Cd0.1 Mn0.1GeAs2 №2 and p-Zn0.9Cd0.1 Mn0.14GeAs2 №3. Initial point of phase transition shifts to lower pressure when content of manganese increases. Baric dependences of Hall coefficient for sample №3 suffers maximum at P=1.5 GPa and saturates at P > 2 GPa. Baric dependences of Hall coefficient for sample №2 has maximum at P=2 GPa and minimum at P=5 GPa. Features of RH(Р) for crystals with more than above 0.06 % mass manganese, where ferromagnetic parameters are expressed more greatly, to our opinion are stipulated by anomalous part of Hall effect and by presence of narrow impurity bands. To determine the mechanism of circuit transition investigation of temperature dependencies of electroconductivity have been carried out in 77-300 K range for samples listed in table 1.
The temperature dependence of sample №2 shows semiconductive character of electroconductivity. At the same time, for samples with manganese content equal to 0.1 and 0.14 mass % metal behavior is characteristic. High temperature activation energy of electroconductivity for the sample with semiconductive character is 0.0874 eV, low temperature - 0.044 eV. In sample with content of manganese 0.1 mass %, electroconductivity in all studied region is characterized by activation energy 0.03 eV over all investigated range. In sample with content of 0.14 mass % activation energy is 0.0448 eV, which is characteristic for high temperature region, has the same value, as for low temperature region for sample with content of Mn 0.06 mass %.
The works was carried out under financial supported by programs of Presidium of the Russian Academy of Science “Heat physics and mechanics of external energy influences and physics of heavily condensed matter”.
[1] L. G. Khvostantsev, et al. , High Temp.-High Pressure 1977, 9, 637. [2] A. Yu. Mollaev, et al., Inorganic Materials 2001, 37, 4, 405.
*E-mail : [email protected] Keywords: Hall coefficients, electroconductivity, temperature
254
Spin reorientation transitions in ferromagnetic semiconductors Cd1-xMnxGeP2 and Cd1-xMnxGeAs2 induced at high pressure
A.Y. Mollaev1, I.K. Kamilov1, R.K. Arslanov1*, T.R. Arslanov1, U.Z. Zalibekov1, V.M. Novotorzev2, S.F. Marenkin2
1Institute of Physics, Daghestan Scientific Center of the Russian Academy of Sciences, 367003, Makhachkala, Russian
2Institute of common and inorganic chemistry of the Russian Academy of Sciences, Moscow, Russian
Magnetic phase transitions were found and studied in ferromagnetic semiconductors Cd1-xMnxGeP2 and Cd1-xMnxGeAs2 according to change of magnetic dynamic penetrability at high hydrostatic pressure up to 9 GPa. Measurement were carried out in high pressure devise of “Toroid” type, dynamic magnetic penetrability μ was measured by fluctuation method, and then recalculated into magnetic susceptibility χ according to formula χ=(μ-1)/4π.
Figures show dependencies of relative magnetic susceptibility χ/χ0 (χ0 – value of magnetic susceptibility at atmospheric pressure) for samples Cd1-xMnxGeP2 and Cd1-xMnxGeAs2. Fig. 2 shows dependence (χ/χ0)(P) for Cd1-xMnxGeAs2. It is seen from figure that maximum (χ/χ0)(P) moves to lower pressures from P=2 GPa for x=0.06 up to P=1.6 GPa for x=0.3 with increase of percent content of manganese (x). The amplitude of maximum on the on the contrary grows with increase of percent content of manganese. The same situation is observed on Cd1-xMnxGeP2 with x=0.9 and x=0.18. It follows from analysis of dependence (χ/χ0)(P) that there takes place spin - reorientation transition ferromagnetic - antiferromagnetic (FM–AFM) in studied samples; the presence of susceptibility shoulder after FM - AFM transition characteristical of antiferromagnetic state testifies it. There were no FM - AFM phase transitions found on base samples Cd1-xMnxGeAs2 and Cd1-xMnxGeP2.
*E-mail : [email protected] Keywords: phase transitions, pressure, ferromagnetic
Fig.1. Baric dependence of relative magnetic susceptibility for samples Cd1-xMnxGeP2 (x=0.09, x=0.18)
Fig.2. Baric dependence of relative magnetic susceptibility for samples Cd1-xMnxGeAs2 (x=0.06, x=0.18, x=0.30)
255
About the high pressure induced negative magneto resistance, found out in the Cd1-xMnxGeAs2
A.Y. Mollaev1, I.K. Kamilov1, R.K. Arslanov1*, T.R. Arslanov1, U.Z. Zalibekov1, V.M. Novotorzev2, S.F. Marenkin2
1Institute of Physics, Daghestan Scientific Center of the Russian Academy of Sciences, 367003, Makhachkala, Russian
2Institute of common and inorganic chemistry of the Russian Academy of Sciences, Moscow, Russian
A negative cross Δρxx/ρ and longitudinal Δρzz/ρ magnetic resistance was found and studied in ferromagnetic high temperature semiconductor (x=0.06, x=0.18, x=0.3). Measurement were carried out in high pressure devises of “Toroid” type, that was placed in multicoil solenoid H < kOe. Figures show dependences (Δρxx/ρ)(P) and (Δρzz/ρ)(P).
It is seen from figure, that magnetic resistance for sample Cd0.7Mn0.3GeAs2 up to pressures P=2.5 GPa is positive and reaches maximum at P≈1 GPa (H=5 kOe). Further increase of pressure leads to suppression of positive magnetic resistance. Magnetic resistance at P>2.5 GPa becomes negative (NMR). Negative magnetic resistance (NMR) at P≈4.5 GPa and H= 5 kOe is about ∼3%. Magnetic resistance at P>6 GPa is positive again. A scattering of circuit carriers on fluctuations of may give a considerable contribution in magnetic resistance up to pressure P<1 GPa – magnetic resistance is positive. There takes place a regulation of ions of spin of manganese with rise of pressure and magnetic field; and it lowers the scattering and leads to NMR; this is confirmed by observed at p=1.6 GPa magnetic phase transition ferromagnetic – antiferromagnetic, (FM–AFM) that takes place in the region of magnetic resistive transition from positive to negative. NMR falls from 3% for x=0.3 up to 1% x=0.06 with the decrease of percent content of manganese (right figure).NMR value depend very much on tension of magnetic field maximum at H= 5 kOe and decrease with fall of magnetic field tension, the position of NMR maximum moves to lower pressures with increase of magnetic resistance tension, also grows the NMR region. A hysteresis is observed at falloff pressure.
*E-mail : [email protected] Keywords: phase transitions, pressure, ferromagnetic
Fig.1. Dependence of cross (circles) and longitudinal (triangles) magnetic resistance from pressure
Fig.2. Dependence of cross magnetic resistance from pressure for samples Cd1-xMnxGeAs2 (x=0.06, 0.18, 0.3)
256
An influence of the hydrostatic pressure on specific resistance, Hall coefficient, and magnetic susceptibility in p-InAs<Mn>
M.I. Daunov, A.Y. Mollaev, R.K. Arslanov*
Institute of Physics, Daghestan Scientific Center of the Russian Academy of Sciences, 367003, Makhachkala, Russia
In monocrystal samples p-InAs<Mn> are measured the specific resistance ρ(P), Hall coefficient RH(P), and magnetic susceptibility χ/χ0, normalized to the atmospheric pressure, at T=300 K in the dependence of pressure up to P=7 GPa. The measurements are carried out in the high pressure apparatus of Toroid” type placed in to the multiturn solenoid with H≤5 kOe. *1, 2+.
The temperature dependences ρ(T) and RH(T) are also measured in temperature range 77÷400 K at atmospheric pressure. In figure are shown the dependences ρ(P) (curve 1), RH(P) (curve 2) and χ/χ0(P) (curve 3).
The baric coefficient of energy ionization for acceptor impure centre of Mn and a dependence of static dielectric conductivity on the pressure are determined. At pressures (2÷6) GPa there are observed a correlation between increase in magnetic susceptibility χ, decrease in hole concentration of the valence band, and respectively, deionization of Mn acceptors (see Fig.).
The works is supported by Russian foundation for basic research (projects 05-02-16608) and project of Presidium of the Russian Academy of Science “Physics and mechanics of highly condensed matter and of the problem of inner structure of the Earth and planets”.
[1] L. G. Khvostanstev, L. P. Vereshchagin, A. P. Novikov, High Press.-High. Temp. 1977, 9, 6, 637.
[2] A. Yu. Mollaev, R. K. Arslanov, L. A. Saypulayeva, S. F. Marenkin, Inorganic materials 2001, 37, 4, 405.
*E-mail : [email protected] Keywords: pressure, specific resistance, Hall coefficient
257
Investigation of polar phonons in CuMIIIO2 (MIII: Al, Ga, Sc) delafossites by means of synchrotron FTIR spectroscopy under high pressure
A. Segura*1,2, J. Pellicer-Porres1,2,C. Ferrer-Roca1,2, P. Dumas3, E. Martinez2, D. Kim4, P. Rodríguez-Hernández1,5, A. Muñoz1,5, A. M. Saitta6
1MALTA-Consolider Team 2ICMUV, University of Valencia (Spain)
3SMIS, SOLEIL Synchrotron (France) 4Pukyong National University, Busan (Korea)
5University of La Laguna (Spain) 6IMPMC, Université Pierre et Marie Curie, Paris (France)
Compounds belonging to the delafossite family CuMO2 (M: Al, Ga, In, Sc, Cr, etc) have recently attracted much attention owing to their p-type conductivity and transparency in the visible range, which makes them interesting for transparent electronics and UV emitting devices [1-2]. Many basic properties of delafossite compounds are not yet well described, in particular the lattice dynamics. Vibrations at the Γ point (space group R3m ) can be decomposed as Γ = A1g + Eg + 3A2u + 3Eu. We have recently investigated CuGaO2 [3] and CuAlO2 [4] lattice dynamics by Raman scattering experiments under high pressure and ab initio calculations. Only the two even modes could be characterized by Raman scattering experiments. In this paper we present an investigation of the odd parity polar modes in three delafossites CuMO2 (M: Al, Sc, Ga) by means of synchrotron FTIR spectroscopy under high pressure.
Single crystal and powdered samples were used for this investigation. Mineral oil was used as pressure transmitting medium for the single crystal while the powdered samples were mixed with KBr before charging the cell. Given the available spectral range at SMIS with a type A MCT detector, only the LO-TO absorption band of the A2u mode could be studied in the three compounds. Above 20 GPa the full Eu absorption band in CuAlO2 could be also studied. The figure shows a typical transmission spectrum for CuAlO2 powder in which the A2u and high energy side of the Eu LO-TO absorption bands are observed (b, c respectively in the figure) as well as a two phonon absorption peak (a). "b" and "c" can be assigned to A2u and Eu LO phonons showing positive pressure coefficients of the order of 5 cm
-1/GPa. From the
frequency and pressure coefficient (7.4 cm-1
/GPa) the "a" peak can only be assigned to Eg+Eu(TO), allowed by selection rules.
[1] H. Kawazoe, M. Yasukawa, H. Hyodo, M. Kurita, H. Yinagi and H. Hosono: Nature 1997, 389, 939.
[2] K. Ueda, T.Hasi, H. Yanagi, H. Kawazoe, H. Hosono, H. Ohta, M. Orita and M. Hirano, J. Appl. Phys. 2001, 89.
[3] J.Pellicer-Porres, A. Segura A, E. Martinez, A.M. Saitta, A. Polian A, J. C. Chervin, B. Canny Physical Review B 2005, 72, 064301.
[4] J. Pellicer-Porres, D. Martínez-García, A. Segura, P. Rodríguez-Hernández, A. Muñoz, J. C. Chervin, N. Garro, and D. Kim, Physical Review B 2006, 74, 184301.
*E-mail : [email protected] Keywords: Synchrotron FTIR, delafossite, polar phonons, high pressure
258
Electroluminescence and band structure in p-AlxGa1-xAs/GaAs1-yPy / n-AlxGa1-xAs under uniaxial compression
E. V. Andreev1, I. V. Berman2, E. V. Bogdanov1, H. Kissel3, K. I. Kolokolov1, N. Y. Minina1*, S.S. Shirokov1, A. E. Yunovich1
1Physics Department, Moscow State University, Russia 2Physics Department, San Jose State University, San Jose, USA
3R&D Department, DILAS Diodenlaser GmbH, Mainz, Germany
Electroluminescence (EL) spectra in p-AlxGa1-xAs/GaAs1-yPy/n-AlxGa1-xAs heterostructures, that have been investigated recently under uniaxial compression up to the pressure P = 4 kbar along [110] and [1-10] directions at 77 K, revealed well pronounced blue shift and 2 ÷ 3 times increase of intensity [1]. The photon energy Eph shift is dEph/dP = 7.2 meV/kbar and dEph/dP = 9.2 meV/kbar for both directions correspondingly.
In the present work the valence- and conduction-band structures of the investigated heterostructure were numerically calculated for different values of the external uniaxial stress along [110] direction. The Luttinger-Kohn Hamiltonian with strain terms was selfconsistently solved using the finite-difference k⋅p method in the framework of the model developed in [2]. The necessary parameters were taken from literature [3]. According to the calculations, the optical energy gap Eg in GaAs0.84P0.16 quantum well (QW) increases under uniaxial compression (dEg/dP = 8.5 meV/kbar) that is in a good quantitative agreement with the electroluminescence data from [1]. At the same time, the energy gaps in Al1-xGaxAs barriers increase in ~ 2.5 times less degree, so the increase of the electroluminescence intensity under compression may be connected with the barrier lowering.
The in-built biaxial tensile strain εxx ≈ 0.58%, that arised in GaAs0.84P0.16 QW because of a strong lattice mismatch, leads to the change of the hole dimensional quantization levels order in QW with light hole level LH1 being the ground state instead of the heavy hole level HH1 in lattice matched A3B5 structures. The calculations indicate that LH1 and HH1 levels move towards each other under uniaxial compression, and after P ≥ 4.5 ÷ 5 kbar HH1 becomes the hole ground state in QW again. The analogous crossover of LH1 and HH1 states was detected in similar GaAs1-yPy/AlGaAs QW diode lasers [4] in dependence on the composition y. In our case, the mixing of light and heavy hole states under uniaxial compression we suppose to investigate in experiments with EL light polarization.
[1] I. V. Berman, E. V. Bogdanov, H. Kissel, N. Ya. Minina, S. S. Shirokov, A. E. Yunovich Phys. Status Solidi b 2009, 246, 522.
[2] K. I. Kolokolov, A. M. Savin, S. D. Beneslavski, N. Ya. Minina, O. P. Hansen Phys. Rev. B 1999, 59, 7537.
[3] I. Vurgaftman, J. R. Meyer, L. R. Ram-Mohan J. Appl. Phys. 2001, 89, 5815. [4] C. J. Poel, H. P. M. M. Ambrosius, R. W. M. Linders, R. M. L. Peeters, G. A. Acket, P. C. M.
Krijn Appl. Phys. Lett. 1993, 63, 2312.
E-mail : [email protected]
259
High-pressure Raman study of zircon structure TmPO4 and observation of a first-order phase transition
E. Stavrou1,2, C. Raptis*1 and K. Syassen2 1Department of Physics, National Technical University of Athens, GR-15780 Athens, Greece
2Max-Planck-Institute für Festköperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
At ambient conditions, Thulium phosphate (TmPO4) crystallizes in the tetragonal zircon structure (D4h
19 space group) with two formula units in the primitive cell. TmPO4 has attracted
interest in the past for its elastic and magnetic properties at low temperatures [1,2]. This crystal displays an anomalous softening with temperature of the shear elastic constant C66
(associated with B2g lattice distortion) which shows a non-zero dip at 20 K [1]. Most crystals with the zircon structure are known [3,4] to sustain an irreversible phase transition to the scheelite structure (C4h
6). In a recent high-pressure Raman study [5], a first-
order phase transition was reported for the isomorphous TbPO4 (at Pc ≈ 9.5 GPa) from zircon to a lower symmetry structure, most likely monoclinic. Such a transition was not observed in
TmPO4 for pressures up to 15 GPa [6]. Since the structure and stability of rare-earth RPO4 phosphates depend on the R
3+ cation size [7] and given the difference between
the Tb3+
and Tm3+
radii, it is reasonable to speculate that a similar (to that of TbPO4) transition will occur in TmPO4
above 15 GPa and with this motivation, we have proceeded to the present work. We have measured the Raman spectra of TmPO4 at pressures up to 22 GPa using a diamond anvil cell. At Pc ≈ 16.5 GPa, abrupt spectral changes have been observed including the appearance of several new phonon peaks and marked discontinuities of phonon frequencies (Fig. 1). These changes imply that TmPO4
undergoes a first-order phase transition to a lower symmetry structure. The transition is irreversible upon decompression to atmospheric pressure. Since the B2g
phonon at 330 cm-1
softens with pressure (Fig.1), it is plausible to expect that the structural distortion leading to the phase transition is of a likewise (B2g) symmetry and therefore this phonon should be related to the transition. Various structures for the high-pressure phase are discussed.
[1] R.T. Harley, D.I. Manning, J Phys C 11, L633 (1978). [2] P. Morin et al, J Phys: Cond Matter 8, 7967 (1996). [3] S. Duclos et al, J Phys. Chem Solids 50, 769 (1989). [4] X. Wang et al, Phys Rev B 70, 064109 (2004). [5] A. Tatsi et al, J Phys: Cond Matter 20, 425216 (2008). [6] E. Stavrou et al, J Phys: Conf Series 121, 042016 (2008). [7] U. Kolitsch, D. Holtstam, Eur J Mineral 16, 117 (2004). *E-mail : [email protected] Keywords: Phase Transitions, Raman scattering, Rare-earth Phosphates, zircon structure
Fig. 1. Frequency-pressure plots of Raman modes of TmPO4
showing a phase transition at P
c ≈ 16.5 GPa.
Solid symbols: compression cycle; open symbols: decompression.
260
Pressure dependence of the electronic subband structure of piezoelectric [311] Ga0.85In0.15As/AlAs superlattices
J. S. Reparaz1, L. R. Muniz1, A. R. Goñi1,*, M. I. Alonso1, G. Rozas2, A. Fainstein2, S. Saravanan3, and P. O. Vaccaro3
1Institut de Ciència de Materials de Barcelona-CSIC, Esfera UAB, 08193 Bellaterra, Spain 2Centro Atómico Bariloche, C1EA, R8402AGP S. C. de Bariloche, Río Negro, Argentina
3ATR Wave Engineering Labs, 2-2-2 Hikaridai, Keihanna Science City, Kyoto 619-0288, Japan
In the last decade, phonon engineering at the nanoscale in purposely designed superlattice (SL) heterostructures mainly based on III-V semiconductors has led to a variety of phononic devices such as mirrors, cavities, and monochromatic acoustic-phonon sources. A main drawback of these systems concerns the weakness of the electron-phonon coupling via deformation potential interaction, which couples acoustic phonons to electrons. This constitutes an intrinsic limitation for the development of multifunctional acoustic devices designed to act on electronic or optical properties. The piezoelectric coupling between electrons and phonons appears as a promising alternative to the deformation-potential mechanism in non-centrosymmetric crystals. Large built-in permanent piezoelectric fields can be readily achieved by SL growth along unconventional crystallographic directions like the [311]. Recently, the resonant enhancement of the Raman scattering by acoustic phonons has been reported[1] for field-activated electronic transitions in a piezoelectric Ga0.85In0.15As/AlAs SL sample grown along the [311] direction. Rozas et al.[1] have pointed out that the piezoelectricity might play the key role to enhance the electron-acoustic-phonon coupling. However, the origin of such transitions remained unclear from their experimental work. For this purpose we have studied the dependence on hydrostatic pressure of the low-temperature (80 K) photoluminescence (PL) to attain deeper insight into the electronic structure of this particular sample. For the optical transitions giving rise to the acoustic-phonon Raman resonance we have obtained a pressure coefficient of -5 meV/GPa, which is
the signature of a Γ→Χ indirect optical transition. Furthermore, by studying the dependence on pressure of the PL peak intensities in the pressure range of the crossover between the direct fundamental optical transition and those linked to the Raman resonance, we obtained strong evidence that for the latter the conduction and valence band states are spatially separated, being the electrons located at the AlAs barrier, whereas the holes are confined to the GaInAs quantum wells. In conclusion, we attribute the resonant enhancement of the
acoustic-phonon scattering in the [311] GaInAs/AlAs SL to type-II, Γ→Χ doubly-indirect (in real and reciprocal space) optical transitions.
[1] G. Rozas, M. F. Pascual Winter, A. Fainstein, B. Jusserand, P. O. Vaccaro, and S. Saravanan, Phys. Rev. B 77, 165314 (2008).
*E-mail : [email protected] Keywords: piezoelectricity, III-V superlattice, photoluminescence, pressure coefficients
261
Multi-phase states in the vicinity of phase transitions
V.V. Shchennikov1*, S.V. Ovsyannikov1, I.A. Komarovskii1, G.V. Vorontsov1, V.V. Shchennikov Jr2
1High Pressure Group, The Institute of Metal Physics, Urals Division of the Russian Academy of Sciences, 18 S. Kovalevskaya Str. Yekaterinburg 620041, Russia
2Institute of Engineering Sciences of RAS, Urals Division, GSP-204, 34 Komsomolskaya Str, Yekaterinburg 620219, Russia
The recent progress in creation of materials with negative refractive index inaccessible for natural substances show all-important role of the multi-phase materials in modern technology. The problem of multi-phase materials has also significant application in the correct determination of the phase transition points and the revealing of the true intrinsic parameters of high-pressure phases. The examples are presented for the well-known materials where high-pressure phase transition is hidden, or vice versa, the additional phase transition has been found based on the recording by the certain properties which are “mixing” in different ways.
In the present paper the approach for multi-phase materials with variable configuration and concentration of inclusions is developed based on interpolation formulas obtained between the rigorously calculated limiting cases of “parallel” and “consequent” electrical, thermal, etc, connection of phases
[1]. This gives an opportunity obtaining algebraic formulas for
complicated properties with the vectors of electrical, thermal, magnetic, etc. forces directed along the different axes for the phase mixtures
[2], and also allows revealing the reliable
parameters of phases in this inhomogeneous state owing to simultaneous measurements of several volumetric, electrical, thermal, thermoelectric, etc. properties of substance
[3].
The model developed allows easily ruling out the above mistakes and obtaining both the true value of phase transition pressure and the intrinsic parameters of high-pressure phases. The results of application of the above approach are given for the analysis of multi-phase states in the vicinity of pressure-induced phase transitions for the certain materials ZnX, HgX, PbX (X – Te, Se, S), etc.
[3].
The research was supported by the Russian Foundation for Basic Research (RFBR) and the Presidium of the RAS Scientific Programme.
[1]. V.V. Shchennikov. Fizika Metallov i Metallovedenie, 1989,7, 93. [2]. V. V. Shchennikov, S.V. Ovsiannikov, G.V. Vorontsov, V.V. Shchennikov Jr. Physica status
solidi (b), 2004, 241, 3203. [3]. V. V. Shchennikov, S.V. Ovsyannikov, A. Y. Derevskov, V. V. Shchennikov Jr, Journal of
Physics and Chemistry of Solids, 2006, 67, 2203.
* E-mail : [email protected] Keywords: phase transition, multi-phase state, configuration of inclusion
262
High-pressure resonance Raman spectroscopy in PbZr0.60Ti0.40O3
J. Rouquette, G. Fraysse, A. Al-Zein, Ph. Papet, J. Haines
Institut Charles Gerhardt UMR CNRS 5253, Université Montpellier II, Place Eugène Bataillon, cc1504, 34095 Montpellier cedex 5, France.
Lead zirconate titanate materials PbZr1-xTixO3 (PZT), are widely used in electronic devices and in other technological applications due to their piezoelectric, ferroelectric, and dielectric properties. PZT solid solutions with compositions near the so-called morphotropic phase boundary, which separates the rhombohedral and tetragonal ferroelectric phases, have been the focus of intense investigations for many years. However, the investigation of the Zr-rich region of the PZT phase diagram is also interesting; for example, the study of the phase transition from the low temperature to the high-temperature rhombohedral phases may be useful in development of thermal detectors. From a structural point of view careful Rietveld refinements yield significantly better agreement factors using monoclinic models for the long-range structure of the Zr-rich PbZr0.60Ti0.40O3, with a Cc space group at low temperature and with a Cm space group at high temperature, rather than the widely accepted rhombohedral symmetry [1]. However, an intrinsic short range order, characterized for example by the presence of diffuse X-ray/neutron scattering in PZT diffraction patterns, i.e local lattice deformations with respect to the average structure, or by large phonon width in vibrational spectra makes structure determination very difficult. In order to determine the phase transition sequence of these disordered materials, we recently used resonance Raman Spectroscopy of a self-trapped exciton emission oxygen deficient complex (TiTi’-VO··) to probe titanium displacements as a function of the temperature [2].
Pressure plays both a major fundamental and a technological role in ferroelectrics.
Ferroelectric properties are dependent on 3 variables (σ,T,𝐸 ). In terms of applications, PZT actuators are for example used for fuel injectors at pressures of up to 2 kbars. Additionally, large stress fields can be observed in miniaturized components or in ferroelectric dots. In this contribution, we present high pressure resonance Raman spectroscopy of PbZr0.60Ti0.40O3. Although the broad vibrational spectra of PZT are consistent with a phonon density of states, we clearly identified two phase transitions based on the dramatic intensity change (a factor of 30). These intensity changes are reproducible in compression-decompression cycles and can, therefore, be related to the evolution of the resonance conditions and thus to the electronic levels involved as a function of the phase transition sequence in PZT materials.
[1] G. Fraysse, J. Haines, V. Bornand, J. Rouquette, M. Pintard, P. Papet and S. Hull, Phys. Rev. B 2008, 77, 064109.
[2] A J. Rouquette, J. Haines, V. Bornand, M. Pintard, Ph. Papet, J.L. Sauvajol, Phys. Rev. B 2006, 73, 224118.
* E-mail : [email protected] Keywords: PZT, phase transition, resonance Raman spectroscopy
263
Indirect carrier leakage in short-wavelength InAs/AlSb quantum cascade lasers
I. P. Marko1, A. R. Adams1, S. J. Sweeney1, R. Teissier2, A. N. Baranov2, and S. Tomić3 1Advanced Technology Institute, University of Surrey, Guildford, Surrey, GU2 7XH, UK
2Institut d’Électronique du Sud UMR5214 CNRS/Université Montpellier 2, 34095 Montpellier, France
3Computational Science and Engineering Department, STFC Daresbury Laboratory, Cheshire WA4 4AD, UK
One of the promising approaches for semiconductor laser applications in the spectral range around 3 μm is based upon the development of short wavelength quantum cascade lasers (QCLs). It has been shown that QCLs can provide high temperature stability and high output powers for wavelengths > 4 μm [1, 2]. It is also anticipated that the use of the short wavelength QCLs will overcome the problem of non-radiative Auger recombination which plagues inter-band lasers working in the same spectral range. One approach to produce short wavelength QCLs utilises the InAs/AlSb materials system, which exhibits the largest separation between direct Γ minimum of InAs conduction band and lowest lateral valleys: X in AlSb and L in InAs, which are about 1.3 eV and 0.72–0.76 eV, respectively [3]. Modelling, however, anticipates that the operation of these short wavelength QCLs may be affected by electron leakage from the upper Γ levels of the laser transition to the states associated with indirect conduction band L-valleys. The importance of this loss process is expected to increase with decreasing lasing wavelength due to the corresponding decrease of the energy separation between Γ and L states. To investigate this we analysed the pressure dependencies of the lasing threshold current, Ith, in two types of InAs/AlSb QCLs operating near 2.9 μm and 3.3 μm as a function of temperature. Since the Γ- and L-minima have different pressure coefficients, high hydrostatic pressure enables one to tune the separation between the Γ and L minima of the conduction band at constant temperature. The lasers investigated were grown by MBE and processed into ridge lasers using wet chemical etching [3]. We assume that the total threshold current is formed by two components: a current due to inter-subband longitudinal optical phonon scattering, Iph, and current loss due to the leakage into the L valleys (the current related to radiative transitions is very small in QCLs and may be neglected). Thus, using the measured pressure dependencies of Ith, the calculated pressure dependencies of optical phonon scattering current [4], Iph, and estimated pressure dependence of the leakage current, Ileak, we show that while carrier leakage from the upper laser levels into the indirect L-valley of the conduction band in InAs quantum wells is negligible in the 3.3 μm QCLs at RT leading to their superior temperature performance, in the shorter wavelength devices emitting at 2.9 μm, this loss mechanism is considerably more important and accounts up to 13% of Ith at 190K, significantly limiting their maximum operating temperature. Hence, for further reduction of the operating wavelength of InAs/AlSb QCLs, carrier leakage into the indirect L-valleys should be minimised to achieve laser operation up to higher temperatures.
[1] Y. Bai at al., APL 92, 101105 (2008) [2] A. Lyakh at al., APL 92, 111110 (2008) [3] J.Devenson et al., APL, 91, 251102 (2007) [4] S.R.Jin et al., APL, 89, 221105 (2006)
264
Buried tunnel junction 2.4-μm GaSb VCSEL investigated by high hydrostatic pressure
I .P. Marko1*, A. B. Ikyo1, A. R. Adams1, S. J. Sweeney1, A. Bachmann2, K. Kashani-Shirazi2 and M.-C. Amann2
1Advanced Technology Institute, University of Surrey, Guildford, Surrey GU2 7XH, UK 2Walter Schottky Institut, Technische Universität München, 85748 Garching, Germany
One promising approach to cover the spectral range between 2 and 3 μm, where several pollutant gases such as CO, CO2, CH4 and NH3 have strong absorption lines, is the development of GaSb-based inter-band lasers. Low-cost, continuous-wave GaSb-based vertical cavity surface emitting lasers (VCSELs) operating at ~2.4 μm up to 50°C have been demonstrated recently [1]. In this work we have used high pressure techniques to investigate ways to improve their performance and extend their working temperature range. Since the band-gap and energy of the gain peak (Ep) increase with pressure at 0.11 meV/MPa at constant temperature, when applied to edge emitting lasers (EEL) we can use pressure to determine the radiative and non-radiative recombination processes occurring. In VCSELs, the pressure also tunes Ep relative to the cavity mode energy Ecm, which has a much weaker pressure dependence. Figure shows the pressure dependence of the threshold current, Ith, of the VCSEL at three different temperatures (263 K, 293 K and 303 K) and of a reference EEL with the same active region (Ith in this case normalised to its value at atmospheric pressure). The decrease in Ith with increasing pressure in the EEL indicates that Auger recombination is dominant at room temperature in this materials system and explains the temperature sensitivity of these EELs. In the VCSEL the pressure dependence of Ith is much more complicated. At -10°C, pressure moves Ep above Ecm and the detuning effect dominates Ith, which therefore increases. At the higher temperatures the decreasing Auger recombination initially dominates. Detailed analysis will be given, but one can immediately note that at ~130 MPa Ith is lower at 20°C and is almost stable with temperature. Therefore we predict that either increasing the band gap or increasing the operating wavelength will allow an improved temperature performance of these GaSb-based VCSELs.
1A. Bachmann et al., Conference Digest, 21st IEEE International Semiconductor Laser Conference, ISLC 2008, 39 (2008).
265
High pressure studies on II-VI ternary alloy Zn1-xBexSe
G. M. Bhalerao*, A. Polian, M. Gauthier
Institut de Minéralogie et de Phyisque des Milieux Condensés, CNRS, Université P. et M. Curie Campus Boucicaut, 140 rue de Lourmel-75015, Paris, France
The II-VI ternary semiconductor alloy Zn1-xBexSe has been studied for its applications in lasers. The binary compound ZnSe is used in blue lasers and substitution of Zn with Be improves its stability against defects generation and propagation. Owing to the large mismatch among the two cations (Zn,Be), the electronic and optical properties vary with concentration x in a nontrivial way[1]. An idea of percolating Be-Se bonds have been put forward to explain the nontrivial evolution of Raman modes, which represent the force constants of the bonds involved[2]. It is required to perform direct measurements of lattice compressibility and bond compressibility in order to set concurrence with the optical results. So, we performed high pressure x-ray diffraction (XRD) and extended x-ray absorption fine structure (EXAFS) studies in order to find the bulk modulus and bond compressibility respectively. Our measurements on the samples with x=0.06-0.55 show that the phase changes from zinc blend to NaCl, which is consistent with literature[3,4]. The phase transformation pressure increases linearly with x. Murnaghan equation of state fitting to the data yields the unit cell volume at ambient pressure and the bulk modulus, both of which were found to increase with x, following the Vegard’s law. EXAFS at both the Zn and Se edges were recorded at Soleil and analysed to find the first nearest neighbor (1NN) distances. Compressibility of the Zn-Se bonds is found to be more than expected from the Vegard’s law. The Zn-Se bonds appear to become ‘harder’ than the average bulk, which is nontrivial. This tendency increases with increasing x and a strong positive bowing in the 1NN distance is observed. These observations indicate to a possibly different response of the Zn-Se and Be-Se bonds to the compressive loading of the ternary alloy. We attribute the observed anomalies to the contrastingly different properties of the two cationic species Zn and Be.
[1] C. Chauvet, E. Tournié, J. P. Faurie, Phys. Rev. B 61, 5332 (2000) [2] A. V. Postnikov, O. Pagès, J. Hugel, Phys. Rev. B 71, 115206 (2005) [3] M. I. McMahon, R. J. Nelmes, Phys. Status Solidi b 198, 389 (1996)
*Email : [email protected] Keywords: Ternary alloys, High pressure, EXAFS, XRD
266
267
Magnetic and Electronic Properties
Lectures Magnetism under pressure in some selected correlated electron systems __________ 269
Evidence for unusual magnetic order in cubic FeGe beyond its quantum phase
transition ________________________________________________________ 270
Magnetism of amorphous iron at pressures up to 35 GPa _______________________ 271
Pressure influence on magnetism in ErCo2 and Er(Co0.975Si0.025)2 ___________________ 272
Superconductivity at 40 K in FeSe under high pressure. __________________________ 273
High pressure structural investigations of Fe-based superconductors ______________ 274
Magnetic order in Tb2Sn2O7 under high pressure: from ordered spin ice to spin
liquid and antiferromagnetic order. __________________________________ 275
Magnetic and spectroscopic characterization of Ni3+
- and Co3+
-doped LaAlO3.
Interplay between spin states and Jahn-Teller effect. ____________________ 276
Effect of high pressure on multiferroic BiFeO3 _________________________________ 277
Filling of the Mott-Hubbard gap in the oxyhalides TiOCl and TiOBr induced by
external pressure _________________________________________________ 278
Evidence for a monoclinic metallic phase in high-pressure VO2 ___________________ 279
The Normal ↔ Inverse spinel configuration crossover in magnetite* ______________ 280
Transparent Dense Sodium ________________________________________________ 281
Posters ME 01 : Magnetism of Lu2Fe17: the effects of Ru substitution, hydrogenation
and external pressure ______________________________________________ 282
ME 02 : High pressure XRD study of β-Na0.33V2O5 _______________________________ 283
ME 03 : High-pressure studies of MFe2O4 (M=Mg, Co, Zn) ferrite spinels: the
dilemma of the post-spinel structure. _________________________________ 284
ME 04 : Electronic state of Fe2+
in (Mg,Fe)(Si,Al)O3 perovskite and (Mg,Fe)SiO3
majorite at pressures up to 81 GPa and temperatures up to 800 K _________ 285
ME 05 : The two polymorphs of CdCr2O4 . _____________________________________ 286
ME 06 : Pressure effect on magnetic properties of La0.67Ca0.33(CoxMn1-x)O3 __________ 287
ME 07 : Electroconductivity of chemical compressed hydrogen in AlH3 under high
multi-shock pressures ______________________________________________ 288
ME 08 : Hydrostatic pressure induced lattice anomalies in High Tc Cuprates _________ 289
ME 09 : Infrared studies of magnetite under high pressure_______________________ 290
ME 10 : High-pressure-induced spin-liquid phase and spin fluctuations in
multiferroic RMnO3 (R=Y, Lu) ________________________________________ 291
ME 11 : Magnetic properties of La0.85Ag0.15(CoxMn1-x)O3 ceramics under pressure ____ 292
ME 12 : Raman study of the E2g phonon in hcp iron: search for magnetic effects _____ 293
ME 13 : Application of Er3+
luminescence as a sensor of high pressure and high
external magnetic field ____________________________________________ 294
ME 14 : Spectroscopic and luminescence properties of (CH3)4NMnCl3. A sensitive
Mn2+
-based pressure gauge. ________________________________________ 295
268
ME 15 : Luminescence of the Nd3+
ion in laser crystals under pressure _____________ 296
ME 16 : Superconducting temperatures of the bcc Ti – V and Zr – Nb alloys at
pressures to 60 GPa _______________________________________________ 297
ME 17 : Pressure dependences of the electrical resistance of Sn2P2S6 crystals.
Models of R( p) dependences________________________________________ 298
ME 18 : Mössbauer study of magnetite under high pressure _____________________ 299
ME 19 : Structural phase relations of iron in dense hydrogen under low
temperature and high-pressure _____________________________________ 300
ME 20 : Insulator to metal transition in compressed YHx (x~3) ____________________ 301
ME 21 : Metal to insulator transitions probed by infrared spectroscopy at high
pressure. ________________________________________________________ 302
ME 22 : Resistivity measurements of the itinerant ferromagnet ZrZn2 under
hydrostatic pressure _______________________________________________ 303
ME 23 : Effects of hydrostatic pressure and uniaxial stress on magnetism in
UNiGa __________________________________________________________ 304
ME 24 : Crystal structure and superconductivity under pressure in the new Fe
based compounds _________________________________________________ 305
ME 25 : Conductivity of CsH5 (PO4)2 under ambient and hydrostatic pressure
conditions _______________________________________________________ 306
ME 26 : High pressure - high temperature elaboration and high pressure study
of new iron arsenides and chalcogenides superconductors _______________ 307
ME 27 : Complex magnetism in Eu2PdSi3 at high pressure studied by 151
Eu-
Mössbauer spectroscopy ___________________________________________ 308
ME 28 : On the pressure dependence of ordering temperature and
magnetization of Y1-xThxCo4B compounds _____________________________ 309
ME 29 : Pressure effect on magnetic properties of Y3Fe62B14 phase in its
amorphous and nano-crystalline states _______________________________ 310
ME30 : Equal-channel multi-angle pressing effect on structure and functional
properties of NbTi alloy ____________________________________________ 311
ME 31 : Effect of internal pressure on structure and magnetism in La1-xREx MnO3
manganites ______________________________________________________ 312
ME 32 : Pressure-induced magnetic and structural transition in the FeCo alloy ______ 313
ME 33 : Low temperature conductivity of NbS3 at pressure induced metal-
insulator transition. _______________________________________________ 314
ME 34 : Direct observation of the antiferrodistorsive phase of SrTiO3 at high
pressure and room temperature _____________________________________ 315
ME 35 : Phase transitions of Fe under high pressure ____________________________ 316
ME 36 : Structural and magnetic phase transitions in the complex perovskite
systems BiMn7O12 and LaMn7O12 ____________________________________ 317
ME 37 : Intercalation- and Pressure- Driven Stabilization of Superconductivity in
1T-TaS2 _________________________________________________________ 318
269
Magnetism under pressure in some selected correlated electron systems
M. M. Abd-Elmeguid
II. Physikalisches Institut, Universität zu Köln, 50937 Cologne, Germany
In strongly correlated electron systems, the metal insulator (MI) transition is driven by strong correlation effects associated with electron-electron interactions and the interplay between the charge, spin and orbital degree of freedom. These are strongly coupled to the lattice and consequently can be tuned by external pressure.
In this contribution, I will present and discuss recent results on the effect of pressure on the magnetic, transport, and structural properties of some selected systems of this class of materials (SmS, RNiO3, and GaNb4S8) with a special emphasis on the appearance of an unconventional metallic state at/ near the pressure- induced MI transition.
It will be shown how such experimental results derived from different high pressure techniques (e.g. electrical resistivity, x-ray and neutron diffraction, nuclear forward scattering) applied to such systems provide new insight in understanding the interplay between these degrees of freedom and their impact on the formation of anomalous ground states under high pressure.
270
Evidence for unusual magnetic order in cubic FeGe beyond its quantum phase transition
H. Wilhelm*1, A .Barla2, M. Forthaus3, C. Strohm4, R. Rueffer4, M. Schmidt5, M.M. Abd-Elmeguid3
1Diamond Light Source Ltd, Chilton, OX11 0DE, UK 2Experiments Division, CELLS-ALBA, 08193 Bellaterra, Barcelona, Spain
3II.Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany 4European Synchrotron Radiation Facility, BP220, 38043 Grenoble, France
5Max Planck Institut für Chemische Physik fester Stoffe, 01187,Dresden, Germany
Transport measurements on the cubic modification of FeGe under high pressure have shown that the long-wavelength helical order (TC = 280 K, at p = 0) is suppressed at a critical pressure pc ~ 19 GPa [1]. The metallic ground state persisting above pc can be described by band-structure calculations if zero-point motion is included. However, the electrical resistivity shows that the ground state can not be described by Fermi-liquid theory in a wide pressure range above pc. This non-Fermi liquid behavior suggests that the phase transition occurs without quantum criticality. New information based on nuclear forward scattering measurements (p < 30 GPa, T > 3 K) revealed a finite but disordered magnetic moment above pc and low temperature. The implication of this finding to the metallic ground state and an updated phase diagram will be discussed.
[1] P. Pedrazzini et al., Phys. Rev. Lett. 98, 047204 (2007).
*E-mail : [email protected] Keywords: FeGe, helical order, non-Fermi liquid, Quantum Phase Transition
271
Magnetism of amorphous iron at pressures up to 35 GPa
M. Lerche1*, D. Haskel2, N. Souta-Neto2, W. Sturhahn2, G. Shen1, K.S. Suslick3 1Carnegie Institution of Washington, 2Argonne National Laboratory, 3University of Illinois
Since the first reported vitrification of a liquid metal alloy in 1959 [1], amorphous metals have been studied extensively. Their physical properties are often distinctively different from those of their crystalline counterparts, see e.g. [2] for an overview. Most of the current experimental data, however, is focused on alloyed amorphous metals. Pure (non-alloyed) metallic glasses are usually far more difficult to produce, because much higher cooling rates are needed to prevent the forming of long range order upon quenching from the melt. The production of on amorphous iron became feasible utilizing acoustic cavitation in 1991 [3]. Its structure up to pressures of 67 GPa was investigated [4], as well as its magnetic properties at ambient and low temperature conditions, see e.g. [5,6]. Here we present experimental results on the magnetism of amorphous iron under pressure up to 30 GPa. The results were obtained using Synchrotron Mössbauer Spectroscopy (SMS) and x-ray magnetic circular dichroism (XMCD). The SMS data show that already at pressure of 6 GPa the magnetic hyperfine field in amorphous iron is less than half that at ambient conditions, it decreases to near zero at 30 GPa. To complement the SMS data additional XMCD measurements we carried out. For the first time, a method was established to compare and combine both datasets. The combined data shows two sharp decreases in the magnetism of amorphous iron, one below 5 GPa and one around 20 GPa. Unlike for crystalline iron, these sharp decreases cannot be associated with a structural transition, since no structural phase transition was found at pressures up to 67 GPa[4]. In order to investigate possible spin transitions as cause for these abrupt changes in the magnetism, X-ray Emission Spectroscopy (XES) was carried out. The results, however, rule out pressure induced spin transitions.
[1] R. H. Willens, W. Klement, Jun., and P. Duwez, Nature 1960, 187, 869. [2] W.L. Johnson, JOM-J. Min. Met. Mater. S., 2002, 54, 40. [3] K. S. Suslick, S.-B. Choet, A. A. Cichowlas, and M. W. Grinstaff., Nature 1991, 353, 414. [4] G. Shen, M. L. Rivers, S. R. Sutton, N. Sata, V. B. Prakapenka, J. Oxley, and K. S. Suslick,
PEPI, 2004, 143, 481 [5] R. Bellisent, G. Galli, M. W. Grinstaff, P. Migliardo, and K. S. Suslick, Phys. Rev. 1993, B48,
15797 [6] G. J. Long, D. Hautot, Q. A. Pankhurst, D. Vandormael, F. Grandjean, J. P. Gaspard, V.
Briois, T. Hyeon, and K. S. Suslick, Phys. Rev., 1998, B 57, 10716
*E-mail : [email protected] Keywords: amorphous metals, magnetism
272
Pressure influence on magnetism in ErCo2 and Er(Co0.975Si0.025)2
D. Turčínková, M. Míšek, J. Prchal, M. Diviš, V. Sechovský
Charles University, Faculty of Mathematics and Physics, DCMP, Prague, Czech Republic
ErCo2 exhibits magnetic ordering at TC = 33 K, where the stable localized Er magnetic moments order ferromagnetically and the itinerant magnetic moments in the Co sublattice stabilize and align antiparallel to the Er moments. This magnetic phase transition is reflected by a pronounced anomaly in the temperature dependence of the AC magnetic susceptibility (a sharp peak) and electrical resistivity (an abrupt drop), respectively. Around TF ~ 100 K the onset of parrimagnetism [1], has been observed which is indicated by a virtually spurious bump in the in the temperature dependence of the AC susceptibility but no anomaly is detectable in resistivity data.
We have prepared polycrystalline samples of ErCo2 and Er(Co0.975Si0.025)2, characterized the crystal structure (the cubic Laves phase has been confirmed in both cases) by X-ray powder diffraction and composition by EDX microprobe. For the two materials we measured temperature dependence of the electrical resistivity and AC susceptibility, respectively and the magnetization curves at selected representative temperatures. The measurements were performed at ambient and high hydrostatic pressures in order to study impact of changes of interatomic distances on the main magnetic characteristics. We have observed the influence of the Si substitution and application of pressure on the Co magnetic moment, Curie temperature TC and the flipping temperature TF. We have confirmed that Si doping yields dramatic increase of TC, reduction of spin fluctuations and stabilization of the Co magnetic moment. On the other hand, a considerably reduced TF value (~ 80 K) has been determined. Both, TC TF are lowered with applying hydrostatic pressure. At high pressures the decoupling of magnetic ordering phenomena in the Er and Co sublattices proposed by Hauser et al. [2] has been indicated in AC susceptibility data. We will present a scenario of physics of ErCo2
considering evolution of exchange interactions and Co moments with respect to substitution and pressure.
[1] J. Herrero-Albillos et al., Physical Review B 76, 094409 (2007). [2] R. Hauser et al., Physical Review B 61, 1198 (2000).
*E-mail : [email protected] Keywords: hydrostatic pressure, itinerant electron metamagnetism, parimagnetism
273
Superconductivity at 40 K in FeSe under high pressure.
S. A. Medvedev*1,2, T. M. McQueen 3, C. Felser 1, M.I. Eremets 2, I.A. Trojan 2, S. Naghavi 1, F. Casper 1, V. Ksenofontov 1, T. Palasyuk 2,4, R. J. Cava 3
1 Institut für Anorganische und Analytische Chemie, 55099 Mainz, Germany 2 Max-Planck-Institute für Chemie, 55128 Mainz, Germany
3 Princeton University, Princeton NJ 08544, USA 4 Institute of Physical Chemistry, Polish Academy of Sciences,01-224,Warsaw, Poland
Superconductivity was discovered recently in iron arsenides [1-5] and FeSe [6,7]. The arsenides display superconducting transition temperatures as high as 55 K and share a number of general features with high-Tc cuprates. Also the binary FeSe show superconductivity under ambient pressure up to 10 K and up to 27 K under modest pressure. In Fe1+δSe the superconductivity is extremely sensitive to stoichiometry [8]. As a significant difference to the arsenides, it was observed that Fe1+δSe is not magnetically ordered down to low temperatures [8]. Here we will discuss the phase diagram of β-Fe1.01Se as a function of pressure. A maximal superconducting transition temperature was found at 37 K under a pressure of 9 GPa. On a first view the phase diagram and the resistivity curve look very similar compared to the iron arsenides [9]. As a function of pressure β-Fe1.01Se shows a transition from a Fermi liquid like transition with a linear resistivity as a function of temperature to a more complex behavior. However, a detailed study of the structural phase diagram at room temperature shows that the hexagonal semiconducting phase seems to be the stable phase, whereas the tetragonal phase is metastable and transform into the hexagonal phase under pressure. A strong drop in the lattice constants was found for modest pressures and at around the 15 GPa tetragonal FeSe becomes cubic. At higher pressures β-Fe1.01Se is fully transformed into insulating hexagonal FeSe. These observations are in excellent agreements with our band structure calculations. The most stable phase is the hexagonal structure, only at ambient pressure the total energy of the hexagonal phase and the tetragonal as well as the orthorhombic phase are the same.
[1] Y. Kamihara, T. Watanabe, M. Hirano, et al., J. Am. Chem. Soc. 2008, 130, 3296. [2] M. Rotter, M. Tegel, D. Johrendt, Phys. Rev.Let., 2008, 101, 107006. [3] K. Sasmal, B. Lv, B. Lorenz, et al., Phys. Rev. Let., 2008, 101, 107007. [4] J. H. Tapp, Z. J. Tang, B. Lv, et al., Phys. Rev. B, 2008, 78, 060505. [5] D. R. Parker, M. J. Pitcher, and S. J. Clarke, arXiv:0810.3214, 2008. [6] F. C. Hsu, J. Y. Luo, et al., PNAS, 2008, 105, 14262. [7] Y. Mizuguchi, F. Tomioka, S. Tsuda, et al., Appl. Phys. Let., 2008, 93, 152505. [8] T. M. McQueen, Q. Huang, V. Ksenofontov, C. Felser, Q. Xu, H. Zandbergen, Y. S. Hor, J.
Allred, A. J. Williams, D. Qu, J. Checkelsky, N. P. Ong, R. J. Cava, arXiv:0811.1613, 2008. [9] C. Hess, A. Kondrat, A. Narduzzo, J. E. Hamann-Borrero, R. Klingeler, J. Werner, G. Behr, B.
Büchner, arXiv:0811.1601.
*E-mail : [email protected] Keywords: pnictides, high pressure, superconductivity
274
High pressure structural investigations of Fe-based superconductors
I. Efthimiopoulos1*, S. Karmakar1, X. Wang1, K. Syassen1, J. S. Kim1, R. K. Kremer1, C. T. Lin1 and M. Hanfland2
1 Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany 2 European Synchrotron Radiation Facility (ESRF), F-38043 Grenoble, France
The recent discovery of superconductivity at 26 K in the doped quaternary iron oxy-pnictide LaFeAsO attracted tremendous scientific interest [1]. More recently, the ternary iron-pnictide family AFe2As2 (R = Ba, Sr, Ca, Eu), adopting the ThCr2Si2 structure (SG I4/mmm), has also been shown to become high-Tc superconductors upon doping [1]. Structural building blocks common to these compounds are square layers built of edge-sharing FeAs4 tetrahedra. These findings indicated the potential for superconductivity in other compounds of similar structure. Subsequently, FeSe (anti-litharge type structure) and LiFeAs were found to be superconducting, even without doping [1].
At ambient pressure, both the AFe2As2 and FeSe compounds exhibit a simultaneous structural (tetragonal to orthorhombic) and anti-ferromagnetic transition upon lowering T [1, 2]. Pressure has been found to be an important variable in these compounds, since it can induce superconductivity (e.g. Tc ~30 K at 4 GPa for BaFe2As2) or raise Tc (Tc ~37 K at ~7 GPa for FeSe) and suppress the aforementioned structural and magnetic transitions [2, 3]. The effect of pressure resembles that of doping, but without the chemical complexity. However, ontroversial results have been reported *3+. In addition, a novel “collapsed” tetragonal (c-T) phase was found to exist in the superconducting regime of CaFe2As2 (structure adopted at ~1.5 GPa at room temperature) [3]. All of the above indicate the strong interplay between the structural and the electronic properties in these compounds. Hence, the pressure-induced modification of the structural parameters becomes an important ingredient for the interpretation and modelling of the superconducting properties.
Here we report the high-pressure structural behavior of two Fe-based superconductors, namely BaFe2As2 and FeSe, investigated at room temperature by means of Raman spectroscopy and synchrotron-based x-ray powder diffraction. For BaFe2As2, the tetragonal I4/mmm phase was found to be stable up to ~25 GPa. The c-T phase was not detected. As for FeSe, we find that the tetragonal phase transforms irreversibly into a hexagonal NiAs-like phase at ~12 GPa, where dTc/dP becomes negative [2]. We do not find any high-pressure orthorhombic phase of FeSe, as reported elsewhere [2]. In both compounds, the FeAs4 (FeSe4) tetrahedra become more distorted under pressure. We compare our results with the findings reported in the literature. We also discuss the correlation between the structural and the electronic/ superconducting properties in these two compounds.
[1] M. V. Sadovskii, arXiv:0812.0302 (unpublished) and references therein. [2] D. Braithwaite et al., arXiv: 0904.1816 (unpublished) and references therein. [3] C. W. Chu and B. Lorenz, arXiv:0902.0809 (unpublished) and references therein.
*E-mail : [email protected]
275
Magnetic order in Tb2Sn2O7 under high pressure: from ordered spin ice to spin liquid and antiferromagnetic order.
I. Mirebeau1*, I.N. Goncharenko1, H. Cao1, A. Forget2 1Laboratoire Léon Brillouin, CEA-CNRS, CE-Saclay, 9191 Gif-sur-Yvette, France
2Service de Physique de l'Etat Condensé, CEA-CNRS, CE-Saclay, 91191 Gif-Sur-Yvette, France.
Rare earth pyrochlores provide text book examples of geometrically frustrated magnets, where exotic short range orders such as spin liquid, spin ices, or chemically ordered spin glasses can be stabilized at T~0 [1]. The rare earth lattice of corner sharing tetrahedra is frustrated both for ferro and antiferromagnetic interactions. Applying pressure results in spectacular changes of the magnetic ground states [2-3], since pressure changes the balance of magnetic interactions and may also play a role in the band structure. In Tb2Ti2O7, spin liquid at ambient pressure, pressure combined with stress induces antiferromagnetic order [2]. This comes from a magnetostriction effect, somewhat similar to that induced under high magnetic field [4]. In Tb2Ti2O7, the lattice expansion induced by Ti/Sn substitution yields an original canted ferromagnetic order, having the local spin structure of a “spin ice” *5+. Namely, the four Tb spins in one tetrahedron have the “two in-two out” structure, a configuration akin to that of the protons in water ice, with the same entropy [6].
What does happen to such “ordered spin ice” under pressure? Could it turn back into a spin liquid? To answer this question, we have studied the Tb2Ti2O7 by neutron diffraction under isotropic pressure of 4.6 GPa, combined with uniaxial pressure of 0.3 GPa, for temperatures 0.2 <T<100K. The ordered spin ice state stabilized at ambient pressure below 1.3 K partly transforms into antiferromagnetic order. But the ordered moment at 0.2 K is reduced, suggesting that spin liquid correlations are enhanced by pressure. The liquid like correlations observed above the ordering transitions are also affected under pressure. We discuss these effects by considering both the influence of stress and isotropic pressure.
[1] Reviews in: S. T. Bramwell, M. J. P. Gingras Science 294, 1495 (2001); R. Moessner and A. P. Ramirez , Physics Today 59, 24, (2006).
[2] I. Mirebeau, I. Goncharenko et al, Nature Nature 420, 54 (2002); Phys. Rev. Lett. 93, 187204 (2004).
[3] A. Apetrei, I. Mirebeau et al, Phys. Rev. Lett. 97, 206401 (2006). [4] A. Cao, A. Gukasov, I. Mirebeau et al, Phys. Rev. Lett 101, 196402, (2008). [5] I. Mirebeau, A. Apetrei et al, Phys. Rev. Lett. 94, 246402 (2005). [6] A. P. Ramirez et al Nature 399, 333, (1999).
*E-mail : [email protected] Keywords : geometrically frustrated magnets, high pressure neutron diffraction
276
Magnetic and spectroscopic characterization of Ni3+- and Co3+-doped LaAlO3. Interplay between spin states and Jahn-Teller effect.
M. N. Sanz-Ortiz*1, F. Rodríguez1, J. Rodríguez1 and G. Demazeau2 1MALTA Consolider Team, DCITIMAC, Facultad de Ciencias, Universidad de Cantabria, 39005 Santander, Spain – 2 ICMCB (UPR-CNRS 9048)-ENSCPB ,Université Bordeaux 1 “Sciences et Technologies” 87 avenue du Dr.A.Schweitzer, 33608 PESSAC Cedex, France
Co3+
and Ni3+
in fluorides and oxides show rather subtle behaviours associated with their spin state [1]. Perovskites AMO3 (M: Ni, Co; A: trivalent lanthanide) exhibit magnetic and electrical properties, which are largely governed by the interplay between orbital ordering, spin state and the Jahn-Teller effect yielding a variety of phenomena such as metal-insulator transition or spin-state dependent related magnetism [2,3]. In connection with these ions it is not yet well understood why Ni
3+ exhibits a low spin state (LS
Ni3+
: t2g6eg
1) at ambient conditions or whether
Co3+
is able to stabilize intermediate spin state (IS: t2g
5eg
1) beyond high spin (HS: t2g
4eg
2) and low
spin (LS: t2g6eg
0) states. In order to clarify their
spin behaviour we have diluted Co3+
and Ni3+
into the diamagnetic LaAlO3 crystal as a way of exploring their spin state in the paramagnetic phase avoiding the exchange effects attained in AMO3. A route of synthesis under high oxygen pressure described elsewhere [4] was employed to stabilize the trivalent valence and avoid aggregation of the transition metal ions.
The oxidation and spin states of both ions were investigated through magnetic measurements and absorption and reflectance spectroscopy. The figure plots the product χT as a function of temperature showing a paramagnetic signal with spin states of S = 1/2 for Ni
3+ and LS S=0 for
Co3+
at low temperatures but increasing with temperature to a IS spin value at room temperature. These data together with optical spectroscopy results indicate that the nearest excited state in Co
3+ is HS state and not IS state. The Jahn-Teller (JT) effect associated with
these states is detected and an estimation of the respective JT distortions is deduced from the optical spectra. The present results open a basic question on whether the IS state is responsible for the observed magnetism in the concentrated compound LaCoO3 [3] or whether an alternative interpretation based on a mixed LS – HS accounts for the measured properties.
[1] M. Imada, A. Fujimori and T. Yoshinori, Rev. Mod. Phys. 1998, 70, 1039. [2] J.L. Garcia-Muñoz, et al., Phys. Rev. B 2004, 69, 094106. [3] D.P. Kozlenko, et al., Phys. Rev. B 2007, 75, 064422. [4] M.N. Sanz-Ortiz, F. Rodríguez, A. Baranov and G. Demazeau, J. Phys. Conf. Ser. 2008, 121,
092003. *E-mail : [email protected] Keywords: Co
3+; Ni
3+; high spin-low spin; high-pressure synthesis; magnetism
277
Effect of high pressure on multiferroic BiFeO3
P. Bouvier1*, R. Haumont2, M. Guennou1, B. Dkhil3, W. Crichton4, J. Kreisel1 1Lab. Matériaux et du Génie Physique (CNRS), Grenoble-INP, 38016 Grenoble, France
2Lab. de Physico-Chimie de l’Etat Solide (CNRS), Paris XI, 91405 Orsay, France 3Lab. Structures, Propriétés et Modélisation des Solides, Ecole Centrale Paris, 92290, France
4European Synchrotron Radiation Facility (ESRF), Grenoble, France
Magnetoelectric multiferroics, which exhibit both magnetic order and ferroelectricity in the same phase, have recently attracted a renewed fundamental interest. Bismuth ferrite BiFeO3 (BFO) is commonly considered to be a model system for multiferroics. The room-temperature structure of BFO is a highly rhombohedrally distorted perovskite with space group R3c[1].
With respect to the cubic Pm3 m structure, the rhombohedral structure is obtained by an antiphase tilt of the adjacent FeO6 octahedra and a displacement of the Fe
3+ and Bi
3+ cations
from their centrosymmetric position along [111]pc. As a consequence of this, BFO presents further to the magnetic order parameter also ferroelectric and ferroelastic order parameters and a complex interplay between these different instabilities should be expected.
We report experimental evidence for pressure instabilities in BFO and namely reveal two structural phase transitions at 3.5 GPa and 10 GPa by using Raman spectroscopy and X-ray diffraction. The above 10 GPa observed nonpolar orthorhombic Pnma (GdFeO3-type) structure is in agreement with recent theoretical ab-initio prediction[3], while the intermediate monoclinic phase was not predicted theoretically. Finally, our results on single crystals will be compared to very recent experimental[4] and theoretical investigations[5] that discuss the occurrence of magnetic and electric phase transitions at 50 GPa in BFO.
[1] P.Fischer, et al., J. Phys. C: Solid State Phys. 13, 1931 (1980). [2] R.Haumont, et al., Phys. Rev. B in press (2009), arXiv:0811.0047v2 [cond-mat.mtrl-sci] [3] P. Ravindran et al., Phys. Rev. B 74, 224412 (2006). [4] A. G. Gavriliuk, et al., Phys. Rev. B 77, 155112 (2008). [5] O. E. Gonzalez-Vazquez and J. Íñiguez, Phys. Rev. B 79, 064102 (2009).
*E-mail : [email protected] Keywords : BiFeO3, Multiferroic, XRD, phase transition
278
Filling of the Mott-Hubbard gap in the oxyhalides TiOCl and TiOBr induced by external pressure
C. A. Kuntscher1*, A. Pashkin1, H. Hoffmann1, S. Frank1, M. Klemm1, S. Horn1, A. Schönleber2, S. van Smaalen2, M. Hanfland3, S. Glawion4, M. Sing4, and R. Claessen4
1Experimentalphysik 2, Universität Augsburg, D-86135 Augsburg, Germany 2Laboratory of Crystallography, Universität Bayreuth, D-95440 Bayreuth, Germany
3European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble, France 4Experimentelle Physik 4, Universität Würzburg, D-97074 Würzburg, Germany
The titanium oxyhalides TiOCl and TiOBr are low-dimensional materials which undergo unconventional transitions to a spin-Peierls state via a structural incommensurate state. With the electronic configuration 3d
1 these compounds are Mott-Hubbard insulators with a charge
gap of approximately 2 eV. They have been discussed to exhibit a resonating valence bond state and high-temperature superconductivity upon doping. However, despite several attempts, up to now a metallization of TiOX (X= Cl, Br) upon doping was not successful.
Our recent pressure-dependent infrared spectroscopic investigations on TiOX [1] suggest that the application of external pressure is an alternative way to induce an insulator-to-metal transition in TiOX. By infrared microspectroscopy we could show the filling of the Mott-Hubbard gap at the critical pressure 16 GPa (14 GPa) for TiOCl (TiOBr) at room temperature. According to our pressure-dependent x-ray powder-diffraction data, the gap closure coincides with a structural phase transitions. These findings are discussed in the context of recent electric transport experiments on TiOCl under pressure [2] and theoretical predictions of pressure-induced phase transitions in TiOCl [3,4].
Financial support by the Deutsche Forschungsgemeinschaft via the Emmy Noether-program, SFB 484, and DFG-CL124/6-1 is gratefully acknowledged.
[1] C. A. Kuntscher et al., Phys. Rev. B 2006, 74, 184402; C. A. Kuntscher et al., Phys. Rev. B 2007, 76, 24110 (R; C. A. Kuntscher et al., Phys. Rev. 2008, 78, 035106.
[2] Forthaus et al., Phys. Rev. B 2008, 77, 165121. [3] Y-Z. Zhang et al., Phys. Rev. Lett. 2008, 101, 136406. [4] S. Blanco-Canosa et al., Phys. Rev. Lett. 2009, 102, 056406.
*E-mail : [email protected] Keyword: Mott transition
279
Evidence for a monoclinic metallic phase in high-pressure VO2
C. Marini1-2, L. Baldassarre1, A. Perucchi1,D. Di Castro1 L. Malavasi3, S. Lupi1, P. Postorino*1
1 “Coherentia” CNR-INFM and Dipartimento di Fisica, Università di Roma” Sapienza”, Roma, Italy
2 Unitá CNISM Roma and Dipartimento di Fisica, Universitá degli Studi “Roma Tre”, Roma, Italy
3 Dipartimento di Chimica Fisica “M. Rolla”, INSTM and IENI-CNR, Università di Pavia, Pavia, Italy
In recent years a number of papers have shown the combined use of optical spectroscopy and high-pressure techniques to be a powerful tool to study the interplay among the different microscopic interactions in strongly correlated electron systems. In particular, when a spontaneous symmetry breaking (e.g. Jahn-Teller or Peierls distortions) triggers a coupling of electronic and vibrational degrees of freedom, the investigation of the pressure dependence of Raman and Infrared spectra enables to disentangle the role of the relevant interactions.
The temperature-driven metal-insulator transition (MIT) of VO2, where a five order of magnitude jump in resistivity is accompanied by a transition from a monoclinic (M1) low temperature insulating phase to a rutile (R) high temperature (T>340 K) metallic phase, is still the subject of intense investigation
[1]. The interest is mainly focused on understanding if the
MIT can be mainly regarded as a Mott-like (electron-electron interaction) or a Peierls-like (electron-lattice interaction) transition. We carried out high-pressure (0-15 GPa) Raman and Infrared measurements at room temperature on a pure and on two lightly Cr-doped VO2 samples. These show insulating behavior at ambient conditions and are found in 3 different monoclinic arrangement (M1, M2, M3) as a consequence of different extents of the Peierls distortion. On applying pressure, all the structures evolve towards a new common monoclinic phase (MX) which clearly show the onset of a metallization process regardless the initial ambient condition structure (M1, M2, M3). Our results thus indicate a major role of the electron correlations, rather than of the electron-phonon, in driving the MIT in vanadium dioxide systems. The new common phase MX, which differently from ambient conditions shows a metallic behavior and Peierls distortions, demands for new experimental and theoretical work.
[1] M. M. Qazilbash, M. Brehm, B.-G. Chae, P.-C. Ho, G. O. Andreev, B.-J. Kim, S. J. Yun, A. V. Balatsky, M. B. Maple, F. Keilmann, H.-T. Kim, D. N. Basov, Science 2007, 318, 1750.
[2] E. Arcangeletti, L. Baldassarre, D. Di Castro, S. Lupi, L. Malavasi, C. Marini, A. Perucchi, P. Postorino, 2007, Phys. Rev. Lett. 98, 196406.
[3] C. Marini, E. Arcangeletti, D. Di Castro, L. Baldassarre, A. Perucchi, S. Lupi, L. Malavasi L Boeri, E. Pomjakushina, K. Conder, P. Postorino, Phys. Rev. B, 2008, 77, 235111.
*E-mail : [email protected] Keywords: insulator to metal transition, spontaneous symmetry breaking, electron-phonon coupling.
280
The Normal ↔ Inverse spinel configuration crossover in magnetite
M. P. Pasternak*, G. Kh. Rozenberg and W. M. Xu
School of Physics, Tel Aviv University, Tel Aviv 69978, Israel
Since the discovery in the late 1930’s of an insulating-metal transition occurring at 120 K, the Verwey transition [1], the structural/electronic/magnetic properties of magnetite (Fe3O4) has become the subject of unrelenting experimental and theoretical investigations. Numerous studies have been carried out since then, among them using Fe-based spectroscopy methods to search for, and experimentally institute, the elusive localization concept but in vain.
At ambient conditions the building blocks of the cubic inverse-spinel (IS) are conjugated (Fe3+-O4)A tetrahedron and of (Fe2.5+O6)B octahedra pairs situated at the spinel’s A and B-sites, respectively. Recently a normal-spinel (NS) configuration has been discovered by means of extensive
57Fe Mössbauer and XRD studies2.
Within the (T,P) landscape the stability limits TNS(P) and TIS(P) of the NS and IS ferrimagnetic configurations have been experimentally determined. At each pressure and at T <TNS the NS configuration dominates and is characterized by Ms= 3μB whereas at T > TIS the IS configuration is characterized by Ms= 2μB. The (P,T) region enclosed by the two limits is designated as ΔT(P). It broadens with P-increase starting with ΔT =2 K at P = 0 reaching 250 K at ~ 25GPa. The ΔT(P) region is characterized by strong spectral fluctuations. The presence of fluctuations and a lack of any detectable volume and symmetry change in the EOS2 clearly points to 2nd-order phase transition which order-parameter responsible for the NS↔IS configuration crossover. The nature of this order parameter is still obscure.
And finally following recent years additional studies regarding the NS↔IS issue the subject will be opened for discussion.
Supported in parts by the Israeli Science Foundation project #478/05
[1] E. J. Verwey, Nature (London) 144, 327 (1939). [2] M. P. Pasternak, W. M. Xu, G. Kh. Rozenberg, R. D. Taylor, and R. Jeanloz, JMMM 265, L107
(2003). G. Kh. Rozenberg, Y. Amiel, W. M. Xu, M.P. Pasternak, M. Hanfland, and R. D. Taylor, Phys. Rev. B 75, 0020102(R) (2007).
*E-mail : [email protected] Keywords: high pressure, magnetite, configuration crossover
281
Transparent Dense Sodium
Y. Ma1,2, M. I. Eremets3, A.R. Oganov2,4, Y. Xie1, I.A. Trojan3,5, S.A. Medvedev3, A.
Lyakhov2, M. Valle6, V. Prakapenka7 1National Lab of Superhard Materials, Jilin University, Changchun 130012, P. R. China
2Laboratory of Crystallography, Department of Materials, ETH Zurich, Wolfgang-Pauli-Str. 10, CH-8093 Zurich, Switzerland
3Max Planck Institute für Chemie, Postfach 3060, 55020 Mainz, Germany 4Geology Department, Moscow State University, 119992 Moscow, Russia
5A.V. Shubnikov Institute of Crystallography, RAS, 117333, Leninskii pr.59, Moscow, Russia 6Data Analysis and Visualization Services, Swiss National Supercomputing Centre (CSCS),
Cantonale Galleria 2, 6928 Manno, Switzerland 7C A R S, University of Chicago, Chicago, Illinois 60637, USA
Under pressure, interatomic distances in materials decrease and the widths of electronic valence and conduction bands are expected to increase, eventually leading to metallization of all materials at sufficiently strong compression (Bloch-Wilson transition); however, core electrons can also substantially overlap at densities achieved with current high-pressure techniques, dramatically altering the electronic properties predicted for archetypes of the free-electron metals lithium (Li) and sodium (Na) and creating Peierls-like distortions, leading in turn to structurally complex phases and superconductivity with a high critical temperature. The most intriguing prediction, of the insulating states due to the pairing of alkali atoms under pressure in Li and Na, has yet to be experimentally confirmed. We showed [1] that at pressures of ≈200 GPa, Na becomes optically transparent (Fig. 1) with the formation of a wide gap dielectric, not in the paired state, but in the monatomic state. This insulating state is formed due to p-d hybridizations of valence electrons and their repulsion by core electrons into the interstices of the six-coordinated highly distorted double-hexagonal close-packed structure. It is possible that such insulating states with localized interstitial electrons play an important role in the physics of strongly compressed matter, possibly existing in the interiors of giant planets and stars.
[1] Ma, Y., et al., Nature, 2009. 458. 182. * E-mail : [email protected] Keywords Sodium, electride, metal-dielectric transition
Fig 1. Sodium clamped in metallic rhenium gasket in between diamond anvils. Photographs are taken through diamond anvil under combined transmitted and reflected illumination. Sodium, a white metal at pressures below 1.1 Mbar turns black at 1.3 Mbar and becomes transparent at 2 Mbar.
282
Magnetism of Lu2Fe17: the effects of Ru substitution, hydrogenation and external pressure
E.A. Tereshina1, A.V. Andreev1*, J. Kamarád1, H. Drulis2 1 Institute of Physics ASCR, Na Slovance 2, Prague 18221, Czech Republic
2 Institute of Low Temperature and Structure Research, Okolna 2, Wroclaw 50-422, Poland
Lu2Fe17 has an antiferromagnetic (AF) structure below TN = 274 K with a transition to the ferromagnetic (F) phase at TC = 130 K [1,2]. The delicate balance of the F and AF Fe-Fe interactions is very sensitive to external conditions and, therefore, Lu2Fe17 is a very convenient object to study the interplay of magnetic field, temperature, external pressure and substitution effects on the magnetism of high-Fe-content intermetallics. External hydrostatic pressure suppresses rapidly the F state in Lu2Fe17 [3,4], stabilizes the AF state and reduces TN due to strengthening of the inter-plane AF interaction and weakening of the intra-plane F interaction upon decrease of the lattice parameters. Interstitial introduction of hydrogen atoms has an opposite effect, i.e. it stabilizes the F state and increases TC. Most substitutions on the Fe sublattice (M = Al, Si, Cr, Mn, Co, Ni) induce a total suppression of the AF phase, preserving only the F state in Lu2Fe17-xMx. Nevertheless, we have recently found that upon Ru substitution, the AF state is stabilized in the whole range of magnetic ordering [5]. The compound with x = 0.5 exhibits a metamagnetic transition with a critical field Bc of 0.9 T which increases under application of external pressure [5].
In the present work, we have studied the effects of hydrogenation (which can be considered as application of negative chemical pressure) followed by application of external hydrostatic pressure on the magnetism of Lu2Fe16.5Ru0.5. The magnetization measurements have been performed on single crystals grown by the Czochralski method in a tri-arc furnace in a Quantum Design SQUID magnetometer using a miniature Cu-Be pressure piston-cylinder cell with a mineral oil as a pressure-transmission medium [6] under pressures up to 1 GPa. Even a low hydrogen content as y = 0.64 in Lu2Fe16.5Ru0.5Hy is found to totally suppress the AF state and to increase the magnetic ordering temperature from TN = 208 K to TC = 290 K. Subsequent hydrogen release down to y ≈ 0.4 leads to a decrease of TC to 272 K and to the appearance of traces of AF phase. Suppression of the F state (with decrease of TC) and restoration of the AF state (TN = 245 K) with a low-field metamagnetic transition (Bc = 0.2 T at 4.2 K) was observed in Lu2Fe16.5Ru0.5H0.64 under hydrostatic pressures up to 0.9 GPa. The results are discussed taking into account the anisotropic change of the lattice parameters in the processes studied.
[1] D. Givord, R. Lemaire, IEEE Trans. Magn. 1974, MAG-10, 109. [2] A.V. Andreev, D. Rafaja, J. Kamarád et al., J. Alloys Compds 2003, 361, 48. [3] J. Kamarád, Z. Arnold, I.V. Medvedeva et al., J. Magn. Magn. Mater. 2002, 242-245, 876. [4] J. Kamarád, O. Prokhnenko, K. Prokeš et al., J. Phys.: Condens. Matter 2005, 17, S3069. [5] A.V. Andreev, J. Kamarad, E.A. Tereshina et al., J. Phys.: Conf. Ser. 2008, 121, 032010. [6] J. Kamarád, Z. Machátová, Z. Arnold, Rev. Sci. Instrum. 2004, 75, 5022.
* E-mail: [email protected] Key words: Rare-Earth Intermetallics; Hydrides; Ferromagnetism; Antiferromagnetism;
283
High pressure XRD study of β-Na0.33V2O5
K. Rabia1, A. Pashkin1, S. Frank1, M. Hanfland2, G. Obermeier1, S. Horn1 and C.A. Kuntscher1*
1Experimentalphysik 2, Universität Augsburg, D-86159 Augsburg, Germany 2European Synchrotron Radiation Facility, BP 220, 38043 Grenoble, France
β-Na0.33V2O5 is a quasi-one-dimensional conductor, which crystallizes in a monoclinic tunnel-like structure built by three kinds of chains along the b-axis, consisting of three inequivalent vanadium sites. Along the b-axis the edge-shared (V1)O6 octahedra form a zigzag chain. The (V2)O6 octahedra form a two-leg ladder by corner sharing, and the (V3)O5 polyhedra form zigzag chains. There are two possible sodium sites located in the tunnels along the b-axis. They can be represented as a two-leg ladder along the b-axis [1]. β-Na0.33V2O5 has remarkable physical properties, such as metal–insulator transition, lowtemperature charge ordering and pressure-induced superconductivity [2]. The superconducting phase is in direct vicinity to a charge-ordered phase, for pressures higher than 7 GPa at 9 K. The mechanism of superconductivity and its relation to the charge ordering is not clear until now.
We have investigated the structural properties of β-Na0.33V2O5 under high pressure up to 20 GPa at room temperature by high resolution angle-dispersive x-ray powder diffraction at the European Synchrotron Radiation Facility Grenoble beamline ID09A. We present here the results of our x-ray powder diffraction investigation. β-Na0.33V2O5 has a monoclinic structure with space group C2/m at ambient conditions. The crystal lattice remains monoclinic up to 20 GPa; however, we observe anomalies in the pressure dependence of the lattice parameters and the volume of the unit cell at around 12 GPa. The compressibility of the b-axis (conducting axis) is smaller compared to the other two axes. These results are consistent with our pressure-dependent optical studies on β-Na0.33V2O5: In the Raman and infrared investigations under pressure up to 15 GPa and 20 GPa, respectively [1,3], most of the spectral features are present up to highest applied pressure. We will discuss the structural changes induced at around 12 GPa.
Financial support by the Deutsche Forschungsgemeinschaft via the Emmy Noether-program and SFB 484 is gratefully acknowledged.
[1] S. Frank, C. A. Kuntscher, I. Gregora, J. Petzelt, T. Yamauchi, and Y. Ueda, Phys. Rev. B. 2007, 76, 075128.
[2] T. Yamauchi, Y. Ueda, and N. Môri, Phys. Rev. Lett. 2002, 89, 057002. [3] C. A. Kuntscher, S. Frank, I. Loa, K. Syassen, T. Yamauchi, and Y. Ueda, Phys. Rev. B. 2005,
71, 220502(R).
*E-mail : [email protected] Keywords: low-dimensional transition-metal oxide, crystal structure
284
High-pressure studies of MFe2O4 (M=Mg, Co, Zn) ferrite spinels: the dilemma of the post-spinel structure.
E. Greenberg*1,2, W.M. Xu1, G. Kh. Rozenberg1, M.P. Pasternak1, A. Kurnosov2, L.S. Dubrovinsky2, M. Hanfland3, G. Garbarino3
1 School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv, Israel 2 Bayerisches Geoinstitut, University Bayreuth, Bayreuth, Germany
3 European Synchrotron Radiation Facility, Grenoble, France.
The spinel structure and its high-pressure (HP) modifications are adopted by many minerals of the upper earth and play an important role in modeling major mineral phases of Earth’s mantle. Therefore the behavior of spinels under non-ambient conditions is of considerable geophysical importance and has been the subject of several studies, in terms of equilibrium properties and phase transformations. Recent HP
57Fe Mössbauer spectroscopy (MS) studies
on magnetite revealed a pressure-induced (PI) first order phase transition at the pressure range 25-35 GPa to an HP phase consisting of two Fe
3+ sites with different quadrupole splitting
(QS) and isomer shift (IS) values. These MS results are incompatible with XRD studies suggesting that the h-Fe3O4 phase has a CaMn2O4- or CaTi2O4-like structure, where both Fe
3+
ions are in identical crystallographic sites. This discrepancy with XRD results initiated the present studies of a series of related normal and inverse ferrite spinels MFe2O4 (M=Co, Zn, Mg).
In the low pressure spinel phase, P-V data from XRD measurements with He or Ne as a pressure medium result in values of the bulk modulus 169<K0<177 GPa for a fixed K’=4 and values of 180<K0<185 GPa with 3<K’<3.7; a clear dependence of the K0 (or K’) on the average cationic radius was observed.
MS, XRD and Raman studies up to 110 GPa revealed for all materials a PI non-reversible first order phase transition to post-spinel HP structures at 25-40 GPa. As in magnetite, according to MS data the HP phase of MFe2O4 ferrites comprises two Fe
3+ sites, with different QS and IS
values. Since it could be unequivocally concluded that the HP post-spinel phases of MFe2O4 ferrite spinels are not of the CaMn2O4 (Pbcm) or CaTi2O4 (Bbmm) structure types. The only possible structure from earlier proposed models is the CaFe2O4 (Pnma) type structure, characterized by two different Fe
3+ sites. Fitting to this structural model gives rather good
results in the case of F(calc) Weighted (model biased) refinement but poor results in the case of a fullprofile Rietveld refinement. HP P-V data results in a large decrease of both the ambient pressure unit-cell volume and the bulk modulus at the transition pressure. Further thorough structural analysis is necessary to resolve the dilemma of the post-spinel structure of ferrite spinels.
*E-mail : [email protected] Keywords: High pressure; spinels, crystallographic transition; Mössbauer spectroscopy.
285
Electronic state of Fe2+ in (Mg,Fe)(Si,Al)O3 perovskite and (Mg,Fe)SiO3
majorite at pressures up to 81 GPa and temperatures up to 800 K
O. V. Narygina*1, I. Yu. Kantor2, C. A. McCammon1, L. S. Dubrovinsky1 1Bayerisches Geoinstitut, Universität Bayreuth, 95440, Germany
2CARS, University of Chicago, IL 60437, USA
Materials with perovskite and garnet crystal structures are very common among dense oxides containing several cations. Iron-bearing magnesium silicate perovskite and majorite (garnet-structured silicate) are very abundant minerals of the Earth’s transition zone and lower mantle. Physical properties (elasticity, thermal and electrical conductivity, etc.) of silicate perovskite is believed to be influenced by the electronic state of iron at high pressures and temperatures. There have been several experimental and theoretical studies on iron spin state in magnesium silicate perovskite at high pressures, but the results are rather controversial.
Recently our group published results of Mössbauer spectroscopy studies of iron behaviour in (Mg,Fe)(Si,Al)O3 at pressures up to 110 GPa
[1]. At about 30 GPa appearance of the new
Mössbauer component with an unusually large value of quadrupole splitting (QS) (about 4 mm/sec) was detected, and the amount of the component increases with pressure and temperature. The new component was assigned to the intermediate spin (IS) 8-12 fold coordinated ferrous iron (
[8-12]Fe
2+) in the perovskite structure. A similar value (3.6 mm/sec)
was previously observed for 8-fold coordinated high spin (HS) ferrous iron ([8]
Fe2+
) in the garnet structure. Since Fe
2+ in perovskite has a similar oxygen environment to garnet we
decided to compare the behaviour of high-QS component in (Mg,Fe)SiO3 perovskite with [8]
Fe2+
component in (Mg,Fe)SiO3 majorite at elevated pressures and temperatures in order to understand whether the origin of a high QS value for
[8-12]Fe
2+ in perovskite is similar to that
one for [8]
Fe2+
in majorite.
Contrary to silicate perovskite (where the amount of high-QS component increases with both pressure and temperature) amount of the
[8]Fe
2+ component in majorite remains the same in
the range of uncertainties at pressures up to 62 GPa and temperatures up to 800K. Good quality of data collected allowed us to calculate energy splitting of eg levels of
[8]Fe
2+ in
Fe0.18Mg0.82SiO3 and Fe0.11Mg0.88SiO3 majorites at 20 GPa and describe the effect of temperature on the QS of
[8]Fe
2+ component in the framework of Huggins model
[2]. While in
the case of silicate perovskite the effect of temperature on the QS of high-QS component can not be described by this model. Based on the differences in high pressure high temperature behaviour of Fe
2+ in perovskite and majorite phases we conclude that the origin of the
components with high QS in these two phases is different. Using a simplified energy diagram for
[8-12]Fe
2+ in perovskite, we confirmed presence of the gradual HS-IS crossover in perovskite
in the pressure range 30-65 GPa.
[1] C. A. McCammon, I. Yu. Kantor, O. V. Narygina, J. Rouquette, U. Ponkratz, I. Sergueev, M. Mezouar, V. Prakapenka and L. S. Dubrovinsky, Nature Geoscience 2008, 1, 684.
[2] F. E. Huggins, Am. Mineral. 1975, 60, 316.
*E-mail : [email protected] Earth’s lower mantle perovskite, spin transition, Mössbauer spectroscopy
286
The two polymorphs of CdCr2O4 .
A. M. Arévalo-López1, E. Castillo-Martínez1, A. Durán1,2, A.J. Dos Santos-García1,3, M.Á. Alario-Franco1*.
1UCM, Madrid, Spain 2CCMC, Ensenada, México 3PCyTA, Albacete, Spain.
CdCr2O4 spinel is a geometrically frustrated antiferromagnet with the Cr3+
ions sited on a pyrochlore lattice.[1] The ordered state is not a simple collinear antiferromagnet, but incommensurate helical spin order along the b-axis.[2] Other chromites (III), crystallize in several structures where the [Cr-O6] octahedra are connected in different ways and this contributes to the differences in their properties.
We report in here the synthesis at high pressure and temperature of a new polymorph of CdCr2O4. In consonance with being a high pressure phase, this is a 10% denser structure than the ambient pressure spinel. The structure consists of infinite chains of staggered edge sharing [Cr-O6] octahedra along the c-axis. These octahedra are linked through oxygen corner sharing along a and b, and the Cd cation seats in triangular prismatic cavities formed by eight O atoms from six octahedra. X-ray and electron diffraction studies show it to be isostructural with CaFe2O4. Rietveld refinement in space group Pnam gives lattice parameters a=9.082(1)Å, b=10.616(1) Å and c=2.9437(4) Å (Figure 1).
Susceptibility measurements (Figure 2) show that the compound follows the Curie Weiss law at high temperature and that the chromium magnetic moments present spin glass behaviour at low temperature. Other physical measurements on this new phase will also be reported and changes with respect to those of the ambient pressure spinel will be discussed.
[1] T. Inami et al. J. Phys. Conf. Series. 2006, 51, 502. [2] J.H. Chung et al. Phys. Rev. Lett. 2005, 95, 247204.
*E-mail : [email protected] Phase transition, Spin glass
Figure 1: β-CdCr2O4 structure.
Figure 2 : 9 and 9-1 vs T
287
Pressure effect on magnetic properties of La0.67Ca0.33(CoxMn1-x)O3
M. Zentková1, M. Mihalik1, Z. Arnold2, J. Kamarád2, G. Gritzner3 1Institute of Experimental Physics, SAS, Košice, Slovakia 2Institute of Physics ASCR, v.v.i., Prague, Czech Republic
3Institute for Chemical Technology of Inorganic Materials, Johannes Kepler University, Linz, Austria
In our paper we compare effects of the hydrostatic and the chemical pressure on magnetic properties of La0.67Ca0.33(CoxMn1-x)O3 ceramics. Hydrostatic pressure was generated by a CuBe pressure cell filled with a mixture of mineral oils serving as the pressure transmitting medium and operating up to 1.2 GPa [1]. Chemical pressure was induced by substitution of Co for Mn (x = 0.01, 0.03, 0.06, 0.1, 0.15), such a substitution leads to reduction of volume of elementary cell. Magnetization measurements were performed in magnetic fields up to 5 T and in the temperature range between 1.8 K and 350 K by a MPMS - SQUID magnetometer. The preparation of the ceramic samples followed the malic acid gel method [2]. All compounds undergo the paramagnetic-ferromagnetic phase transition in the temperature range from 240 K down to 60 K. We have found that the hydrostatic pressure increases the Curie temperature TC (Fig.1.). In the case of the ceramic with x = 0.03 the increase can be described by the pressure coefficient ΔTc/Δp = 26 K/GPa. Magnetization saturates under hydrostatic pressure at higher magnetic field in comparison with ambient pressure but the saturated magnetization μs does not change with applied pressure (Fig.2.). Basic magnetic quantities, the Curie temperature and the saturated magnetization are reduced by substitution of Co for Mn [3]. We will discuss this opposite tendencies in more details in our paper.
[1] M. Zentková, Z. Arnold, M. Mihalik, A. Zentko, J. Kamarád, Z. Mitróová, S. Maťaš, J. Electrical Eng . 2006, 57, 29.
*2+ G. Gritzner, J. Ammer, K. Kellner, V. Kavečansky, M. Mihalik, S. Maťaš, M. Zentková, Applied Physics A-Materials Science & Processing, 2008, 90, 359.
*3+ M. Mihalik, S. Maťaš, M. Zentková, G. Gritzner, J. Electrical Eng . 2008, 59, 29.
*E-mail : [email protected] Keywords (manganites, magnetic properties, hydrostatic pressure, chemical pressure)
Fig.1. Effect of pressure on μ(T).
Fig.2. Effect of pressure on μ(B).
288
Electroconductivity of chemical compressed hydrogen in AlH3 under high multi-shock pressures
D.V. Shakhray, A.M. Molodets, V.E. Fortov
Institut of problem of chemical physics, Chernogolovka, Russia
A study of electrophysical and thermodynamic properties of alane AlH3 under multi shock compression has been carried out. The increase in specific electroconductivity of alane at shock compression up to pressure 100 GPa have been measured. High pressures and temperatures were obtained with explosive device, which accelerates the stainless impactor up to 3 km/sec. The impact shock is split into a shock wave reverberating in alane between two stiff metal anvils. The conductivity of shocked alane increases in the range up to 60-75 GPa and is about 30 1/Ohm*cm. In this region the semiconductor regime is true for shocked alane. The conductivity of alane achieves approximately 500 1/Ohm*cm at 80-90 GPa
*E-mail : [email protected] shock wave, electrical conductivity, high pressure
289
Hydrostatic pressure induced lattice anomalies in High Tc Cuprates
E. Siranidi*1, D. Lampakis1, E. Liarokapis1, A. Gantis2, M. Calamiotou2, I. Margiolaki3 and K. Conder4
1National Technical University, Athens, Greece 2University of Athens, Athens, Greece
3ESRF, Grenoble, France 4Paul Scherrer Institute, Villigen, Switzerland
We present the results of high pressure (up to 7 GPa) micro-Raman data in comparison with high pressure (up to 13GPa) synchrotron angle-dispersive powder diffraction experiments on different high Tc cuprates. The Raman data for the superconducting YBa2Cu3Oy (with y=6.5 and 7) compounds have shown that in the pressure region 2.5-4 GPa there is no increase in the Ag phonon energy despite the increase in pressure [1]. This softening of the four Ag phonons is in contrast to their almost linear behavior for the non superconducting Pr123. Additionally, the phonon width indicates that the Y123 (both y=6.5 and 7) has an unusual pressure dependence compared to Pr123. At the same time the c-axis values of Y123 exhibit a strong deviation from the expected equation of state in the region 3.7-10 GPa [2], while the optimally doped LSCO (x=0.15) compound shows a clear deviation from the Murnaghan equation for p~3.5 GPa and a hysteresis. No such deviation is observed in the non superconducting Pr123 and La2CuO4 (LCO) compounds at least for pressures < 8GPa. Furthermore, excess FWHM with strong hysteresis for the (110) and (113) lines (at the same pressure range where Raman modes do not harden) have been observed for the superconducting Y1237 and LSCO (x=0.15) compounds, but not for the non-superconducting Pr123, LCO. The analysis of the bond lengths indicate that the pressure induced anomalies in the Raman and XRD data are related with charge redistribution between the c- and a-axis, which apparently affects the transition temperature. Although we cannot anticipate the behavior of the other cuprates, our up-to-now data reveal a systematic anomaly in the cuprates, which could provide a hint about the role of the lattice in the high Tc superconductivity.
[1] D. Lampakis, E. Liarokapis, J. Karpinski, C. Panagopoulos and T. Nishizaki, Journal of Superconductivity: Incorporating Novel Magnetism 17, 121 (2004).
[2] M. Calamiotou, A. Gantis, D. Lampakis, E. Siranidi, E. Liarokapis, I. Margiolaki, K. Conder, EPL 85, 26004 (2009).
*E-mail : [email protected] Keywords: high pressure Raman spectroscopy, high pressure X-ray diffraction, phase separation, high Tc superconductors
290
Infrared studies of magnetite under high pressure
J. Ebad-Allah1, L. Baldassarre1, 2, M. Sing3, R. Claessen3, V.A.M. Brabers4, and C.A. Kuntscher1*
1 Experimentalphysik 2, Universität Augsburg, D-86135 Augsburg, Germany 2 Sincrotrone Trieste S.C.p.A., in Area Science Park, I-34012 Basovizza, Trieste, Italy
3 Experimentelle Physik 4, Universität Würzburg, D-97074 Würzburg, Germany 4 Dep. of Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
Magnetite (Fe3O4) is a material with many puzzling properties. It undergoes a Verwey transition at Tv≈120 K at ambient pressure, which can largely be described as a disorder-to-order transition, accompanied by changes in the crystal structure and the latent heat, and a two orders of magnitude decrease of the dc conductivity. At ambient conditions magnetite has an inverse cubic spinel structure [Fe
3+]A[Fe
2++Fe
3+]BO4, where A and B denote the
tetrahedral and octahedral sites, resp., in the spinel structure AB2O4 [1]. The conduction mechanism is established to be polaron hopping through the octahedral sites of the Fe
2+ and
Fe3+
ions. It was recently suggested that magnetite undergoes at room temperature a pressure-induced phase transition from the inverse spinel to the normal one, i.e., [Fe
2+]A[Fe
3++Fe
3+]BO4, above 6 GPa, without any change in the lattice symmetry [3]. This
proposal is, however, controversially discussed [4].
We studied the electronic and vibrational properties of magnetite at room temperature as a function of pressure by infrared reflectivity measurements. The goal of our study was to verify the conduction mechanism via polaron hopping and furthermore to search for signatures of the phase transition at around 6 GPa, for a clarification of its character. Our findings are as follows: The optical conductivity shows the two expected T1u phonon modes and a pronounced midinfrared band consistent with earlier infrared studies at ambient conditions [5]. With increasing pressure we observe a redshift of the midinfrared band. Also, the spectral weight grows at low frequencies and a new feature appears in the far-infrared range. These findings will be discussed regarding the two issues mentioned above (conduction mechanism and pressureinduced phase transition).
Financial support by the Bayerische Forschungsstiftung and the Deutsche Forschungsgemeinschaft via the SFB 484 is gratefully acknowledged.
[1] S. Sasaki, Acta Crystallogr. B. 1997, 53, 762. [2] N. F. Mott, Philos. Mag. B. 1980, 42, 327. [3] M. P. Pasternak et al., Magn. Magn. Mater. 2003, 265, L107; M. P. Pasternak et al., J. Phys.
Chem. Solids. 2004, 65, 1531; G. K. Rozenberg et al., Phys. Rev. B. 2007, 75, 020102. [4] S. V Ovsyannikov et al., J. Phys. Cond. Mat. 2008, 20, 172201. [5] L. V. Gasparov et al., Phys. Rev. B. 2000, 62, 7939.
*E-mail : [email protected] Keywords: infrared spectroscopy, polarons
291
High-pressure-induced spin-liquid phase and spin fluctuations in multiferroic RMnO3 (R=Y, Lu)
D.P. Kozlenko1*, I. Mirebeau2, J.-G. Park3, I.N. Goncharenko 2, S. Lee3, and B. N. Savenko1
Joint Institute for Nuclear Research, 141980 Dubna, Russia Laboratoire Leon Brillouin, CEA-CNRS, CE Saclay, 91191 Gif-sur-Yvette, France
Department of Physics, SungKyunKwan University, Suwon 440-746, Republic of Korea
The hexagonal manganites MnO3 ( =Ho, Er, Tm, Yb, Lu, Y, Sc) are a unique class of materials, exhibiting multiferroic phenomenon in combination with frustrated low dimensional magnetism on triangular lattice
[1]. In these compounds, the ferroelectric
transition temperature ~ 600–900 K is much higher in comparison with the antiferromagnetic (AFM) ordering temperature, ~ 70–130 K. At TN the spontaneous ferroelectric polarization exhibits a sharp increase by about 10 %, correlated with a distortion of triangular lattice. It reflects a strong interplay of ferroelectric and magnetic properties via magneto-elastic coupling
[2].
The crystal and magnetic structure of hexagonal YMnO3 and LuMnO3 have been studied by means of powder neutron diffraction at high pressures up to 7 GPa. In YMnO3, an application of high pressure leads to an appearance of the spin liquid state, coexisting with the minority
of the suppressed initial ordered triangular AFM state of 1 irreducible representation symmetry, as evidenced from the analysis of the magnetic diffuse scattering
[3]. An appearance
of the spin liquid state affects significantly the multiferroic properties and implies a rapid reduction of magneto-elastic coupling and the relevant ferroelectric polarization change in the vicinity of TN.
In LuMnO3 the triangular AFM state of a different 2 irreducible representation remains stable under pressure, but considerably reduced value of the ordered magnetic moment also signals an increase of spin fluctuations under pressure
[4]. From the analysis of the available
experimental data a generalized magnetic phase diagram of RMnO3 hexagonal multiferroic manganites, linking the magnetic state symmetry, the strength of spin fluctuations and the distortion of the triangular lattice, was deduced
The work has been supported by RFBR, grant 09-02-00311a.
[1] J. Park et al., Phys. Rev. B 68, 104426 (2003). [2] S.Lee et al., Nature 451, 805 (2008). [3] D.P.Kozlenko et al., Phys. Rev. B 78, 054401 (2008). [4] D.P.Kozlenko et al., J. Phys.: Condens. Matter 19, 156228 (2007).
*E-mail : [email protected] Keywords : multiferroic, neutron diffraction, spin liquid, magnetic structure
292
Magnetic properties of La0.85Ag0.15(CoxMn1-x)O3 ceramics under pressure
M. Mihalik1, M. Zentková,1 Z. Mitróová1, G. Gritzner2 1Institute of Experimental Physics, SAS, Košice, Slovakia
2Institute for Chemical Technology of Inorganic Materials, Johannes Kepler University, Linz, Austria
Magnetic properties of La0.85Ag0.15(CoxMn1-x)O3 ceramics (x = 0.00, 0.01, 0.03) have been studied in pressure range up to 0.9 GPa. Hydrostatic pressure was generated by a CuBe pressure cell filled with a mixture of mineral oils serving as the pressure transmitting [1].Magnetization measurements were performed in magnetic fields up to 5 T and in the temperature range between 1.8 K and 300 K by a SQUID magnetometer. The preparation of the ceramic samples followed the malic acid gel method [2]. We have found that the hydrostatic pressure increases the Curie temperature TC (Fig.1.) and can be described by the pressure coefficient dTc/dp = 14.2 K/GPa. Magnetization saturates under hydrostatic pressure at lower magnetic field in comparison with ambient pressure but the saturated magnetization μs does not change with applied pressure. The magneto-caloric effect in these compounds is considerably large and higher than in other perovskite compounds in which La is substituted by divalent alkali-earth elements [3]. We measured magnetization isotherms under pressure to study the effect of pressure on the magneto-caloric effect in La0.85Ag0.15(CoxMn1-x)O3.
*1+ M. Zentková, Z. Arnold, M. Mihalik, A. Zentko, J. Kamarád, Z. Mitróová, S. Maťaš, J. Electrical Eng . 2006, 57, 29.
[2] G. Gritzner, J. Ammer, K. Kellner, V. Kavečansky, M. Mihalik, S. Maťaš, M. Zentková, Applied Physics A-Materials Science & Processing, 2008, 90, 359.
[3] Nguyen The Hien, Nguyen Phu Thuy, Physica B, 2002, 319, 168.
*E-mail : [email protected] Keywords (manganites, magnetic properties, hydrostatic pressure, magneto-caloric effect)
Fig.1. Effect of pressure on temperature dependence of magnetization.
293
Raman study of the E2g phonon in hcp iron: search for magnetic effects
Yu. S. Ponosov
Institute of Metal Physics UD RAS, Ekaterinburg, Russia
Hexagonal-close-packed (hcp) phase of iron has been synthesized more than 50 years ago but the question of ground state in this iron polymorph is still open. Recent density functional theory (DFT) calculations have predicted an antiferromagnetic (AFM) ground state [1] at least in low pressure range but so far no one Mossbauer experiment has detected hyperfine splitting to low temperatures [2]. Since taking the AFM state into account leads to much better description of experimental equation of states for hcp iron, hypothesis to explain this contradiction has been proposed [3]. It was partly based on Raman experiment which has found the splitting of the E2g phonon in hcp iron and iron-nickel alloys at low pressures [4]. The authors [4] suggested that the occurrence of satellite mode may be activated by some kind of disorder in a proximity to the transition boundary (bcc-hcp) or the strong anharmonicity of the E2g mode. The calculations [3] found that such splitting may be induced by spin-phonon interaction in the orthorhombic antiferromagnetic structure (afmII) of iron, which is stable, as calculated within DFT. It was proposed [3] that quantum spin fluctuations in hcp iron (in the absence of static antiferromagnetism) may be responsible for better accuracy of magnetic DFT calculations for elastic properties and for the observed Raman splitting and superconductivity.
While the properties of pure hcp iron should be studied under pressure, iron alloys with hcp structure (FeMn, FeRu, FeOs) may be investigated at ambient pressure. Experiments have found the evidences that an antiferromagnetic state exists in these alloys at low temperatures. In this work we present new Raman results concerning pressure and temperature behavior of the E2g phonon in iron and its alloys and compare found dependences with previous data and DFT simulations.
This work was supported by the Russian Foundation for Basic Research by the grant # 08-02-00437.
[1] G. Steinle-Neumann, L. Stixrude & R. E. Cohen Phys. Rev. B, (1999), 60, 791. [2] A. B. Papandrew et al., Phys. Rev, Lett., (2006), 97, 087202. [3] G. Steinle-Neumann, R. E.Cohen, and L. Stixrude, J. Phys. Condens. Matter, (2004), 16,
S1109. [4] A. F. Goncharov, V. V. Struzhkin, J. Raman Spectrosc., (2003), 34, 532.
*E-mail : [email protected] Raman, pressure, hcp iron, magnetism
294
Application of Er3+ luminescence as a sensor of high pressure and high external magnetic field
R. Valiente * 1, M. Millot 2, F. Rodríguez 3, J. González 3, J. M. Broto 2 1 MALTA Consolider Team, Dpto. de Física Aplicada, Facultad de Ciencias,
Universidad de Cantabria, Santander, Spain 2 Laboratoire National des Champs Magnétiques Intenses (LNCMI )-CNRS-UPR3228,
Université de Toulouse, 143 avenue de Rangueil,31400 Toulouse, France 3 MALTA Consolider Team, DCITIMAC, Facultad de Ciencias,
Universidad de Cantabria, Santander, Spain
The combined effect of high hydrostatic pressures and high external magnetic fields on the photoluminescence (PL) properties of materials has not been studied so far in the literature. Among optically active ions, rare-earth ions are known to reveal luminescence from multiple excited states. Upconversion process is a way to transform low energy photons into higher energy photons. The most efficient upconversion system up to now is based on Er
3+ and Yb
3+.
It is possible to observe, by the naked eye, visible PL from Er3+
after Yb3+
excitation in the near-infrared.
In this work we present the effects of high pressure (up to 7.5 GPa) on the upconversion properties of Er
3+-Yb
3+ co-doped single-crystal thin films of KY(WO4)2 [1] under external
magnetic fields up to 56 T at 100 K. Measurements were carried out in a non-magnetic titanium-based diamond anvil cell. The external magnetic field was applied along the
crystallographic b-axis of a microcrystal of about 100 m 100 m and a thickness of about
30 m. The detailed study of the green 4S3/2
4I15/2 Er
3+ PL around 550 nm after
2F7/2
2F5/2
Yb3+
excitation around 1 m as a function of pressure and external magnetic field reveals the potential applicability of this type of systems as pressure and external magnetic field sensors
at the same time. The use of inexpensive broad-width ( 5 nm) laser diodes ensures the required tuning among the Zeeman levels either by direct Er
3+ excitation (in the blue) or
through Yb3+
excitation (around 980 nm) along the pulse duration of the external magnetic field.
Measurements were done under pulsed magnetic fields at the Laboratoire National des Champs Magnétiques Intenses (LNCMI) in Toulouse. The complete experimental setup has been described in refs. [2,3].
[1] Y. E. Romanyuk, I. Utke, D. Ehrentraut, V. Apostolopoulos, M. Pollnau, S. García-Revilla and R. Valiente, J. Cryst. Growth 2004, 269, 377
[2] M. Millot, S. George, J.-M. Broto, B. Couzinet, J.-C. Chervin, A. Polian, C. Power, and J. González, High Pressure Research 2008, 28, 627.
[3] M. Millot, J.-M. Broto, and J. González, Phys. Rev. B 2008, 78, 155125.
*E-mail : [email protected] Keywords: pressure sensors; photoluminescence; high external magnetic field
295
Spectroscopic and luminescence properties of (CH3)4NMnCl3. A sensitive Mn2+-based pressure gauge.
L. Nataf1, F. Rodríguez*1, R. Valiente2 and J. González1 1MALTA Consolider Team, DCITIMAC, Facultad de Ciencias,
Universidad de Cantabria, 39005 Santander, Spain 2MALTA Consolider Team, Dpt. Física Aplicada, Facultad de Ciencias,
Universidad de Cantabria, 39005 Santander, Spain
The (CH3)4NMnCl3 crystal (TMMC) consists of linear chains of face-sharing MnCl64-
octahedra, which has received considerable attention as a one-dimensional (1D) system. In particular, 1D-Heisenberg magnetism
[1,2] and exciton migration processes governing the
photoluminescence (PL) properties in 1D systems [3]
were mostly investigated on this material. Its strong anisotropy and exchange interaction between Mn
2+ ions are responsible for the large
crystal-field strength of the Mn2+
ions (Δ = 0.8 eV)
[4] yielding an intense PL band at 633 nm at
ambient conditions. Recent correlation studies between structural and magnetic properties under high pressure conditions
[2] reveal that
crystal compression is anisotropic, the MnCl64-
increasing its axial distortion along the chain (hexagonal c axis) with pressure. This structural variation favours an increase of both Δ and the splitting of the emitting
4T2 state making it
candidate to exhibit large PL pressure shifts. The figure shows the variation of the time-resolved emission spectra of TMMC as a function of pressure. It is worth noting the big PL shift shown in the 0 – 10 GPa range. The shift rate is two orders of magnitude bigger than ruby, its PL intensity being higher in spite of the different peak width
[5]. These particular features make this crystal especially attractive for using as
pressure gauge, particularly, in those experiments requiring precise determination of pressure variations below tenths of GPa.
A correlation study between crystal and electronic structures in TMMC as a function of pressure will be presented at the Conference. The effects of exchange interaction in the exciton migration and PL efficiency will be analyzed as well.
[1] J. I. Zink, Gordon, E. Hardy, and G. Gliemann, Inorg. Chem. 1980, 19, 488. [2] S. Tancharakorn, F. P. A. Fabbiani, David, R. Allan, K. V. Kamenev, and N. Robertson, J. Am.
Chem. Soc. 2006, 128, 9205. [3] R. Knochenmuss and H. U. Güdel, J. Chem. Phys. 1987, 86, 1104. [4] Y. Rodriguez-Lazcano, L. Nataf and F. Rodriguez, J. Lumin. 2009, to appear. [5] K. Syassen, High Pressure Research 2008, 28, 75.
*E-mail : [email protected] Keywords: TMMC; pressure sensors; photoluminescence; time-resolved spectroscopy
1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8
7.1 GPa
4.0 GPa
Photon energy (eV)
1.96 eV
(633 nm
1.74 eV
713 nm)
1.62 eV
767 nm)
0 GPa
Incre
asi
ng
pre
ssu
re
50 meV/GPa
(19 nm/GPa)
296
Luminescence of the Nd3+ ion in laser crystals under pressure
S. F. Leon-Luis*1, U.R. Rodríguez-Mendoza1, D. Jaque2, J.E. Muñoz-Santiuste3, V. Lavín1
1 MALTA Consolider Team, Dpto. de Física Fundamental y Experimental, Electrónica y Sistemas. Universidad de La Laguna. E-38200 San Cristóbal de La Laguna, Santa Cruz de
Tenerife, Spain 2 GIEL, Dpto. de Física de Materiales, Facultad de Ciencias. Universidad Autónoma de
Madrid, 28049 Madrid, Spain 3 MALTA Consolider Team, Dpto. de Física Aplicada, Escuela Politécnica Superior.
Universidad Carlos III de Madrid. Avda. del Mediterráneo 20913, Leganés, Madrid, Spain.
We report the effect of pressure on the near-IR luminescence of the Nd3+
ion in YAG (Y3Al5O12), GGG (Gd3Ga5O12) and YAB (YAl3B4O12) laser crystals and/or ceramics using laser spectroscopy techniques with a diamond anvil cell. In the YAG and GGG garnets, the rare-earth ions are incorporated as a dopant in the structure of the crystal lattices substituting the Y
3+ or the Gd
3+ ions respectively, showing a D2 local point symmetry which belongs to the
orthorhombic symmetry [1]. On the other hand, in the YAB crystal the rare earth ions are situated in a D3 crystal-field substituting the Y
3+ ions[2]. For all these laser crystals the
pressure-induced evolutions of the emission spectrum corresponding to the 4F3/2→
4I9/2,
4I11/2
transitions are measured from ambient pressure up to 13 GPa, where no crystal phase transitions are observed, using a cw Ar
+ laser in multiline mode. A gradual red shift and an
increase of the splitting of the emission bands have been observed with increasing pressure [3]. The former can be ascribed to a pressure-induced decrease in the Slater and spin-orbit interactions, whereas the latter increases due to the stronger crystal-field interaction of the optically active ion with its oxygen ligands with compression. The energy shifts of the R1,R2→Z5 transitions obtained for these laser crystals are compared with the R lines of ruby for their consideration as alternative pressure calibrants in the NIR region. [4]
This work has been partially supported by Ministerio Ciencia e Innovación (MAT2007- 65990-C03 and MALTA Consolider Ingenio 2010 CSD2007-00045) and EU-Feder funds.
[1] Hong Hua, Sergey Mirov and Yogesh K. Vohra. Phys. Rev. B 9, 6200 (1996) [2] M. H. Bartl, E.C. Fuchs, K. Gatterer, H.P. Fritzer, M. Bettinelli and A. Speghini. Journal of
Solid State Chemistry 167, 386 (2002) [3] Thomas Tröster. Handbook on the Physics and Chemistry of rare Earths. Vol 33, 515
(2003). Elservier Science B.V. [4] S. Kobyakov, A. Kaminska, A. Suchocki, D. Galanciak and M. Malinowski. Appl. Phys. Lett.
88, 234102 (2006).
* E-mail : [email protected] Keywords: High-Pressure, luminescence, Nd3+, laser crystal
297
Superconducting temperatures of the bcc Ti – V and Zr – Nb alloys at pressures to 60 GPa
I.O. Bashkin, V.G. Tissen, E.G. Ponyatovsky
Institute of Solid State Physics, Chernogolovka, Moscow district, 142432, Russia
The superconducting transition temperatures of the body-centered cubic Ti – V and Zr – Nb alloys are measured in dependence on pressure to about 60 GPa using the diamond anvil technique.
It is found that the Tc(P) dependences of the Zr – Nb alloys have two anomalies: a shallow minimum or a kink in the pressure range 5–10 GPa and a broad maximum at higher pressures. This behavior of Tc(P) is similar to that earlier observed on pure metal Nb
[1]. A comparison
with recent model calculations suggests that the features of the Tc(P) behavior in the Zr – Nb alloys are of the same nature as in pure Nb and result from the high-pressure anomalies in their phonon spectra.
The Tc(P) dependences of the Ti – V alloys also show a similar-shaped low-pressure anomaly, but the high-pressure behavior is different. A peak-shaped anomaly appears in a narrow pressure interval around 20 GPa, which can be assumed to be due to a structural transition in the alloy. At higher pressures, Tc(P) dependences of the Ti – V alloys are increasing, as in the case of pure vanadium
[2]. Our accurate measurements on vanadium demonstrated that the
low-pressure anomaly is also characteristic of pure metal.
The concentration dependence, Tc(c), at a fixed pressure represents a curve with a maximum for both systems. The difference in the Tc(P) behavior of two systems belonging to the IV and V rows of the Periodic Table may be assumed to be due to the difference in the specific volumes.
[1] V.V. Struzhkin, Y.A. Timofeev, R.J. Hemley, H.K. Mao, Phys. Rev. Lett. 1997, 79, 4262. [2] M. Ishizuka, M.I. Ketani, S. Endo, Phys. Rev. B 2000, 61, R3823.
*E-mail : [email protected] Superconductivity, transition metal alloys
298
Pressure dependences of the electrical resistance of Sn2P2S6 crystals. Models of R( p) dependences
Y. Tyagur1, I. Tyagur2 1Uzhgorod National University, 46 Pidhirna str., UA-88000 Uzhgorod, Ukraine
2International Center for Piezoelectric Researh, Technical University of Liberec, Studentsja 2, CZ-461 17 Liberec 1, Czech Republic
Tinhypodiphosphate (Sn2P2S6) crystals exhibit good ferroelectric, photoelectric and semiconductor properties [1-3]. The second order phase transition close to the tricritical point with change of the symmetry PC ↔ P21/C is realized at the temperature Т0 = (339±3) К. Applied high hydrostatic pressure on the sample leads to decreasing of the phase transition temperature. Pressure dependence of the temperature T(p) at different pressures over the region (0 ≤ p ≤ 0.7 GPa) in cooling mode is well described by the following exponential
equation: 𝑇 𝑝 = 𝑇0 . 1 − 𝑝
𝑝0 𝑛
, where T (336.80 0.61)K is the temperature of the phase
transition at the atmospheric pressure, p (1.35 ± 0.15)GPa is the pressure of the phase transition at 0 K, n = (0.91 ± 0.12) is the exponent.
Pressure measurements of the electrical resistance R( p) at different temperatures of the Sn2P2S6 crystals are presented. The monodomain, unipolar and polydomain samples of Sn2P2S6 were investigated. It is established, that dependence R( p) is decreasing with applied pressure in ferroelectric and paraelectric phases. In the vicinity of the phase transition pressure( 0 p ), dependence R( p) shows an anomaly allied to the phase transition under the influence of the pressure. For monodomain and unipolar ferroelectric phase, dependence R(
p) is describled by the following equaiton: 𝑅(𝑝)
𝑅01= 1 −
𝑝
𝑝0 𝑛
, where R01 is the value of the
electrical resistance in ferroelectric phase at atmospheric pressure and definite temeprature, p0 is a value of a phase transition pressure, n is the exponent. For unipolar ferroelectric phase, mentioned parametes are the following: p0 = 0.196 GPa, n = 0.027 at T = 292.0 K. For monodomain ferroelectric phase those parameters are: p0 = 0.22 GPa, n = 0.15 at T = 286.5 K . Hence, pressure dependence R( p) is described by the following exponential function in any case of behaviour of the relative pressure coefficient ( p) T a versus pressure: quadratic, linear or just a constant: R(p) = R0 exp( D0 + D1.p + D2.p
2 + D3.p
3), where R0, D0, D1, D2, D3 are the
paremeters. Dependence R( p) is described by the exponential function, in case the inverse dependence of the relative coefficient (αT(p))
-1 T a is linear function
[1] R. Nitsche, P. Wild, Mat. Res. Bull, 5, 419 (1970). [2] Y.I. Tyagur, Ferroelectrics 345, 91 (2006). [3] Yu. Vysochanskii , et al . Phase transitions in phosphorus chalcogenide crystals. Vilnius,
2006.-453p.
E-mail : [email protected]
Keywords: electrical resistance, pressure, ferroelectric
299
Mössbauer study of magnetite under high pressure
K. Glazyrin*1, C. McCammon1,L. Dubrovinsky1, K. Schollenbruch2 1Bayerishes Geoinstitut Universität Bayreuth, Bayreuth, Germany
2Institut für Mineralogie J.W.Goethe-Universität, Frankfurt, Germany
Recent works on magnetite have shown how little we know about how pressure influences its physical properties. Rozenberg et al.[1] made an assumption an inverse-normal spinel transition at ~20 GPa as a result of Mössbauer and x-ray analysis. In more recent work Ding et al.[2] suggested an intermediate spin transition (IST) at 12-16 GPa. Conventional Mössbauer spectroscopy is very sensitive to mentioned transitions but unfortunately previous works lack detailed analysis of Mössbauer parameters. We present results on pure Fe3O4 loaded into diamond anvil cell and studied in pressures up to 60 GPa. Neon was used as quasi hydrostatic pressure medium.
We were able to extract Mössbauer parameters: central shift (CS) and hyperfine magnetic field (HF) for tetrahedral and octahedral positions as well as parameters for high pressure positions (HP1, HP2) and new phase (Fig. 1, Fig. 2). We could not observe IST, proposed by Ding et al. on octahedral sites at 12-16 GPa, but we observed a high spin-low spin or high spin-intermediate spin transition at high pressures P>27 GPa, as seen from behavior of HF on
Fig. 2. Our data (IS and HF) also show no inverse-normal spinel transition at 20 GPa.
[1] G. Kh. Rozenberg, Y. Amiel, W. M. Xu, M. P. Pasternak, R. Jeanloz, M. Hanfland, and R. D. Taylor, Phys. Rev. B, 2007, 75, 020102(R).
[2] Yang Ding, D. Haskel, S.G. Ovchinnikov, Y-C. Tseng,Y.S. Orlov, J.C. Lang, and H-K. Mao, Phys. Rev. Lett., 2008, 100, 045508.
* E-mail : [email protected]
magnetite high-pressure mössbauer
Fig. 2 Hyperfine magnetic field Fe3O4 vs pressure
Fig. 1 Central shift of Fe3O4 vs pressure
300
Structural phase relations of iron in dense hydrogen under low temperature and high-pressure
Y. Ohishi*1, N. Hirao1, T. Matsuoka1, T. Mitsui2, K. Takemura3, A. Machida2, K. Aoki2 1Japan Synchrotron Radiation Research Institute (JASRI/SPring-8),
Sayo, Hyogo 679-5198, Japan 2 Japan Atomic Energy Agency (JAEA), Sayo, Hyogo 679-5148, Japan
3National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044, Japan
Iron-hydride (FeHx) is synthesized at 3.5 GPa in dense hydrogen at room temperature, and is unique in its melting curve, its phase relation, and its magnetism [1]. The insertion of hydrogen in iron leads to dramatic changes in the volume and electronic structure of host metal Fe, resulting in the ferromagnetic double hexagonal-close-packing (dhcp)-FeHx, in contrast to the nonmagnetic hcp-Fe. By using a new energy-domain synchrotron radiation 57
Fe-Mossbauer spectroscopy technique [2], we observed the magnetic transition from the ferromagnetic to nonmagnetic state on the dhcp-FeHx near 27 GPa without structural phase transitions [3]. In order to understand the electronic and magnetic properties of FeHx, it is important to perform high-pressure and low-temperature experiments on FeHx. However, the phase relations of FeHx remain unknown. Here we report the synthesis and stability field of FeHx in the system of Fe–H under high-pressure and low-temperature conditions with in-situ synchrotron x-ray diffraction in a diamond anvil cell.
We performed low-temperature/high-pressure experiments on the Fe-H system for structural observations by x-ray diffraction at SPring-8/BL10XU [4] along various P-T paths. FeHx was synthesized neither by cooling down to 12.5 K at 1 GPa, nor by pressurizing up to 25 GPa at 160 K. Meanwhile, at 18 GPa and 160 K we observed the bcc-hcp phase transition in the Fe-H system, which is in good agreement with pure-iron, and also no volume expansion by insertion of H on the hcp phase. During decompression after warming up to room temperature, we observed the drastic expansion of the lattice constant accompanied by the dissolution of hydrogen at 13 GPa corresponding to the hcp-bcc phase boundary of pure-iron. This result indicates an appearance of a new phase. We will demonstrate the structural and magnetic properties of the new phase in more detail.
[1]Y. Fukai, The Metal-Hydrogen System. Springer, Berlin, 2000. [2] T. Mitsui et al., Jpn. J. Apl. Phys. 2007, 46, L382. [3] N. Hirao et al., in preparation. [4] Y. Ohishi et al., High Pressure Research. 2008, 28, 163.
* E-mail : [email protected] Keywords: iron-hydride, phase relation, low-temperature/high-pressure, synchrotron x-ray diffraction
301
Insulator to metal transition in compressed YHx (x~3)
T. Matsuoka1,2, H. Nugyen2, Y. Nakagawa2, K. Shimizu2, Y. Nakamoto2, T. Kagayama2, Y. Ohishi1, A. Machida3, K. Aoki3
1JASRI/SPring-8, Kouto, Sayo, Hyogo 679-5148, Japan, 2KYOKUGEN, Osaka University, Toyonaka, Osaka 560-8531, Japan,
3Synchrotron Radiation Research Center, JAEA/SPring-8, Kouto, Sayo, Hyogo 679-5148, Japan
Yttrium hydride (YHx) switches its electronic property from shiny metal to transparent insulator with the variation of the x. With the value of x above 2.8, YHx transits from metal to insulator[1]. The lattice of yttrium metal atoms form hcp lattice and hydrogen atoms are located in interstitial sites. Previously, Ohmura et al have reported the abrupt band gap closure in infrared region at around 25 GPa and claimed the possibility of the pressure induced insulator-to-metal transition in compressed YH3[2]. We have previously performed simultaneous measurements of electrical resistance and X-ray diffraction on YHx (x~3), in SPring-8 BL10 XU, and found electrical resistance decreases significantly with the structural transition from hcp to fcc[3,4]. But, the clear evidence of metallic character was not obained[3,4]. For the purpose to investigate the electrical properties of YHx in more detail, we have performed again electrical resistance measurements on YHx with x considered to be 3 or much closer to 3 than previous our studies. The electrical resistance measurements were performed up to 70 GPa and 1.6 K using diamond anvil cells and refrigerators. The electrical resistance increases with increasing pressure in hcp phase and its temperature dependence showed clearly semiconductor character, negative resistance (R) vs. temperature (T) slope. In fcc phase, electrical resistance decreased by 3 orders of magnitude and the R vs. T curve changed its slope to positive, characteristic of metal, near 40 GPa. This study provides the experimental evidence of insulator to metal transition in compressed YHx (x~3).
[1] J. N. Huiberts, R. Griessen, J. H. Rector, R. J. Wijngaarden, J. P. Dekker, D. G. de Groot and N. J. Koeman, Nature 380, 231(1996).
[2] A. Ohmura, A. Machida, T. Watanuki, and K. Aoki, PRB 73 104105 (2006). [3] A. Machida, A. Ohmura, T. Watanuki, K. Aoki, and K. Takemura, PRB 76 052101 (2007). [4] T. Matsuoka, T. Kitayama, K. Shimizu, Y. Nakamoto, T. Kagayama, K. Aoki, Y. Ohishi and K.
Takemura, High-Pressure Research 26, 391 (2006).
*E-mail : [email protected]
Keywords metal-hydride, insulator to metal transition
302
Metal to insulator transitions probed by infrared spectroscopy at high pressure.
L. Baldassarre*1, A. Perucchi1, P. Postorino2 and S. Lupi2 1 Sincrotrone Trieste S.C.p.A., in Area Science Park, I-34012 Basovizza, Trieste, Italy
2 CNR-INFM Coherentia and Dipartimento di Fisica, Universita di Roma "La Sapienza", Piazzale Aldo Moro 2, I-00185 Roma, Italy
Several families of transition metal oxides display metal to insulator transitions (MIT) often driven by both temperature (T) and pressure (P) with jumps of conductivity up to 7 orders of magnitude [1]. Infrared spectroscopy is a powerful tool to determine how the electrodynamics evolves across the metal to insulator transition, since it probes both electronic and lattice degrees of freedom, allowing the understanding of the mechanisms that drive the MIT.
We will report about the IR studies performed as a function of pressure at SISSI, the infrared beamline at ELETTRA Synchrotron facility in Trieste, and then focus on two compounds belonging to the Magnéli phases of vanadium oxides.
The MIT has been widely investigated in several of these compounds [2], however often the mechanism that drives the electronic transition is yet unclear, due to a subtle interplay between electron-phonon and electron-electron interactions.
Here we present a complete investigation of MIT as a function of T and P, by measuring the optical properties of single crystals of V
2O
3, (V
0.989Cr
0.011)2
O3
, and V3
O5
[3].
Measurements have been performed in a wide range of T (10-600 K) and P (0-15 GPa) in order to cover the rich phase diagrams of those materials.
[1] M. Imada, A. Fujimori and Y. Tokura, Rev, Mod. Phys 1998, 70, 1039. [2] E. Arcangeletti L. Baldassarre , D. Di Castro, S. Lupi, L. Malavasi, C. Marini, A. Perucchi, and
P. Postorino, Phys. Rev. Lett. 2007, 98, 196406. [3] L. Baldassarre, A. Perucchi, E. Arcangeletti, D. Nicoletti, D. Di Castro, P. Postorino, V.A.
Sidorov and S. Lupi, Phys. Rev. B 2007, 75, 245108.
*E-mail : [email protected] Keywords: metal-insulator transition, synchrotron infrared radiation
303
Resistivity measurements of the itinerant ferromagnet ZrZn2 under hydrostatic pressure
LA Sibley*1, JR Wensley1, E Pugh1, 2, C Liu1, GG Lonzarich1, N Kimura3, S Takashima4, M Nohara4, H Takagi4
1Cavendish Laboratory, University of Cambridge, Cambridge, UK 2 Nottingham Trent University, Nottingham, UK
3 Tohoku University, Sendai, Japan 4 University of Tokyo, Tokyo, Japan
We present a high pressure, low temperature (to 50 mK) study of the weak itinerant ferromagnet ZrZn2. The low Curie temperature and small ordered moment of this material make it ideal to use pressure to tune the ferromagnetic transition to low temperatures with pressures less than 2 GPa. Using a Diamond Anvil Cell, with a low noise four terminal resistivity set up, we observe the suppression of the ferromagnetic transition, to the formation of a Quantum Critical Point around a critical pressure of 2 GPa.
Previous high pressure measurements show deviations from the Fermi Liquid description of matter at low temperatures below the critical pressure (evidenced by a T
5/3 form of the
resistivity) which can most likely be explained in the framework of a marginal Fermi Liquid [1]. Above the critical pressure a new phase was observed [2] as evidenced by a T
3/2 form of the
resistivity. The exact nature of this new phase is as yet unknown. In our measurements we have confirmed the existence of this new phase and the extent of this phase is investigated to higher pressures.
[1] R.P. Smith, M Sutherland, G.G. Lonzarich, S.S. Saxena, N. Kimura, S. Takashima, M. Nohara, H. Takagi, Nature 2008, 455, 1220-1223.
[2] S Takashima, M Nohara, H Ueda, N Takeshita, C Terakura, F Sakai, H Takagi, J Journal of the Physical Society of Japan 2007, 76 No. 4, 043704.
*E-mail : [email protected] ZrZn2, Quantum Critical Point, Diamond Anvil Cell, Heavy Fermion
304
Effects of hydrostatic pressure and uniaxial stress on magnetism in UNiGa
M. Míšek 1,2* J. Prokleška1, J. Kamarád2, P. Javorský1,V. Sechovský1 1Charles University, Faculty of Mathematics and Physics, DCMP, Prague, Czech Rep
2 Institute of Physics, Academy of Sciences of the Czech Rep., 182 21 Prague 8, Czech Rep.
In this work we present the results of magnetization measurements of UNiGa single crystal (field along c-axis) under high hydrostatic pressures up to 0.9 GPa as well as effect of uniaxial stress applied along the c-axis of the hexagonal ZrNiAl–type crystal structure (space group
P6 2m). UNiGa has been selected because of the number of magnetic structures propagating along the c-axis adopted at various temperatures and magnetic fields. It orders antiferromagnetically below TN ~ 39 K and three more order-to-order transitions between different AF phases were observed with further decreasing temperature [1,2]. The phases are characterized by collinear magnetic structures with uranium magnetic moments locked along the crystallographic c-axis. The ground state was found to be characterized by the + + − + − − coupling with the ordered uranium magnetic moments μ ~ 1.4 μB [2]. With applying a magnetic field along the c-axis the transition to the field induced ferromagnetic structure (directly for T < 10 K or via the + + − structure at higher temperatures) was observed *2+. Given the magnetic structures propagating along c-axis, besides hydrostatic pressures, also an application of uniaxial stress is of natural concern.
We measured both the temperature dependencies of magnetization in the external magnetic fields and the magnetic isotherms under various high hydrostatic pressures up to 0.9 GPa and uniaxial stress up to 0.2 GPa applied along c-axis. Measurements were carried out in the MPMS 7T SQUID magnetometer (Quantum Design) using the clamped Cu-Be pressure cell and uniaxial pressure cell recently developed in the High pressure laboratory of Institute of Physics AS CR [3], respectively. With application of hydrostatic pressure we observed both gradual suppression of AF phases existing in 34 – 39 K at ambient pressure and low fields and a pressure induced increase of the critical fields of metamagnetic transitions below 34 K. Measured data qualitatively agreed with previous results [2], however, significant quantitative disagreement was observed.
In case of uniaxial-stress application, measured data clearly deviate from behavior observed in hydrostatic-pressure experiment. A scenario explaining the observed phenomena in terms of different variations of exchange interactions with application of hydrostatic-pressure and uniaxial-stress will be presented.
To support a proper discussion of observed phenomena (UNiGa is known for strong dependency on stoichiometry), specific-heat, thermal expansion, magnetostriction and resistivity data measured on the same piece of crystal will be presented, as well.
[1] V. Sechovský, L. Havela, K. H. J. Buschow (Ed.): Handbook of Magnetic materials, Vol.11, North-Holland, 1998
[2] F. Honda et al., 1998, J. Alloys Comp. 271-273, 495-498, and references therein [3] J. Kamarád et al., 2008, High Press. Res. 28, 633-639
*E-mail : [email protected]
305
Crystal structure and superconductivity under pressure in the new Fe based compounds
G. Garbarino1, P.Toulemonde2, M. Mezouar1, P. Lejay2, S. Clarke3, A. Palenzona4, W. Crichton1, and M. Núñez Regueiro2
1 European Synchrotron Radiation Facility, Grenoble, France 2 Institut Néel, CNRS & Université Joseph Fourier, Grenoble, France
3 Department of Chemistry, University of Oxford, Oxford, UK 4 CNR/INFM-LAMIA Genova & Dipartimento di Chimica e Chimica Industriale, Genova, Italy
The study of the crystal and electronic structure under pressure is a powerfull tool that helps to find clues to analyze the superconducting state. The case of the new iron based superconductors is an excellent example, where there are still plenty of opened questions to be answered.
In this presentation, we will discuss the effect of structural parameters under pressure on the superconducting properties on compounds belonging to the four representative Fe based families. In particular, we report the evidence of different structural phase transitions under pressure, for example in the case of FeSe the high pressure phase induce an increase in the superconducting transition temperature (TC) with a maximum at 34K[1]. We have observed similar behaviors in other compounds[2,3]. The effect on TC of some characteristics parameters under pressure, like the inter(intra)layer distance, the angle Fe-As(Se)-Fe, are discussed in detail.
[1] G. Garbarino, et al, EuroPhys. Lett., 2009, 86, 27001 [2] G. Garbarino et al, Phys Rev B (R) 2008, 78, 100507 [3] M. Mito, M. Pitcher, W. Crichton, G. Garbarino et al, J. Am. Chem. Soc, 2009, 131, 2986
*E-mail : gaston.garbarino @esrf.fr Keywords: superconductivity, high pressure, crystallography, electronic properties
Figure 1: Dependence of the normalized volume with pressure for various of the studied compounds belonging to the four representative Fe based families.
306
Conductivity of CsH5 (PO4)2 under ambient and hydrostatic pressure conditions
M. Zdanowska-Frączek*1, Z. J. Frączek1, G. V. Lavrova2, V. G. Ponomarieva2
1 Institute of Molecular Physics, Polish Academy of Sciences, Poznań, Poland 2 Institute of Solid State Chemistry, Siberian Branch of Russian Academy of Sciences,
Novosibirsk, Russia
The solid acids, hydrogen-bonded crystals of the MxHy(AO4)z composition (where M=Cs, Rb, K, Na, Li, NH4; A=S, Se, As, P) have been attractive for researchers on account of ferroelectric properties, the salts exhibit in low temperatures. Recently, it has been found that some of them have highly conductive phases with dynamically disordered networks of hydrogen bonds. The simple crystal structure and well defined location of protons make these salts an interesting molecular model system for charge transport studies in hydrogen bonded materials. It is generally accepted that proton transport proceeds in framework of the two stage Grotthuss mechanism. The conductivity process includes: intrabond motion (proton transfer within hydrogen bonds) and intrabond transfer (the hydrogen bonds breaking together with the reorientation of ionic groups involved in hydrogen bonds formation). Simple theoretical models demonstrate how pressure can be used as a “tuning knob” for their properties. Up till now no experimental evidence of this has been encountered.
The new CsH5 (PO4)2 salt belongs to the solid acids family. The conductivity of the CsH5 (PO4)2 crystals has been studied by impedance spectroscopy as a function of temperature (from 140K up to 419K), pressure (up to 350 MPa) and time. The experimental data have shown that above room temperature conductivity of the CsH5 (PO4)2 crystal rapidly increases and above Ts=418 K achieve considerably high value (~ 10
-2 S/cm) at ambient pressure. The electrical
properties of studied crystal have been found pressure sensitive. The crystal conductivity rapidly decreases versus pressure and periodical charge fluctuations appear. The time dependent studies (at constant pressure and temperature conditions) were carried out in order to clarify the nature of this phenomena. Under specific conditions, rapid nonlinear increase of crystal conductivity with large fluctuations at low frequencies were observed. This state became stable after about 50 hours, and can be frozen by temperature decreasing. This process is reversible. The results have been discussed within the phenomenological model.
*E-mail : [email protected] Keywords: electric conductivity, solid acids, impedance spectroscopy, charge transport,
307
High pressure - high temperature elaboration and high pressure study
of new iron arsenides and chalcogenides superconductors
P. Toulemonde1*, G. Garbarino2, M. Álvarez-Murga1, A. Sow1, P. Strobel1, P. Lejay1, A. Sulpice1, M. Mezouar2, M. Núñez Regueiro1
1Institut Néel, CNRS & Université Joseph Fourier, Grenoble, France 2 ESRF, Grenoble, France
One year ago, the discovery of high temperature superconductivity in layered arsenides based on iron in tetrahedral site by the group of H. Hosono in Japan has received a huge interest in the community of condensed matter physicists. We will present our work in this field.
Using high pressure – high temperature, we have synthesized LnFeAs(O1-xFx) with Ln = La or Sm [family Ln-1111] and (Ba1-xLax)Fe2As2 superconducting compounds. Fluorine and lanthanum substitution in these two compounds induces an electron doping of the parent antiferromagnetic LaFeAsO and BaFe2As2 systems which become superconducting for a particular range of dopant level. For 10 % of fluorine La-1111 and Sm-1111 superconduct at Tc = 20 K and 45 K respectively.
In the Ln-1111 family we have attempted to introduce a chemical pressure induced by substitution of arsenic for phosphorous. We have compared the effect on the crystallographic structure and superconducting properties with the one obtained by mechanical pressure on the pure As based Ln-1111 compound [1].
We have also studied the analogous superconducting family based on iron in chalcogen tetrahedron FeCh4 with Ch = Se, Te. The properties of Fe1+δ(Se1-xTex) compounds obtained by high pressure high temperature synthesis and by conventional sealed quartz tube method were compared at room pressure. Our samples were also studied by x-ray diffraction under high pressure and resistivity under pressure at low temperature. The results will be discussed.
[1] G. Garbarino, P. Toulemonde, M. Álvarez-Murga, A. Sow, M. Mezouar, and M. Núñez-Regueiro, Phys. Rev. B 2008, 78, 100507.
[2] G. Garbarino, A. Sow, P. Lejay, A. Sulpice, P. Toulemonde, M. Mezouar and M. Núñez-Regueiro, Europhys. Lett. 2009 (April 2009), 86, issue 2, 27001.
*E-mail : email: [email protected] Keywords: high pressure – high temperature synthesis, high pressure crystallography, superconductivity
308
Complex magnetism in Eu2PdSi3 at high pressure studied by 151Eu-Mössbauer spectroscopy
G. Wortmann1*, K. Rupprecht1, B. Bielemeier1, E.V. Sampathkumaran2 1University of Paderborn, Department of Physics, D-33095 Paderborn, Germany
2Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005, India
Eu2PdSi3 belongs to a class of rare-earths intermetallics with AlB2-type hexagonal structure exhibiting various forms of complex magnetism [1,2]. This behaviour is due to two different Eu sites, the 2b site named R1 and the 6h site named R2, occurring in a ratio of 1:3. In Eu2PdSi3, both Eu sites are divalent, the minority R1 site exhibit ferromagnetic (fm) order at 40 K, while the majority R2 site exhibits antiferromagnetic (afm) order around 10 K [1]. In the 151
Eu-Mössbauer spectra, the R1 and R2 sites can be clearly distinguished by their different isomer shifts, S = - 8.6 mm/s and -10.0 mm/s as well as by their different saturation hyperfine fields, Bhf = 414 kG and 262 kG, respectively [1].
The application of high pressure has a dramatic effect on the magnetic properties of Eu2PdSi3: First one immediately realise from the spectrum at 300 K that a valence transition towards Eu
3+ has occurred for the R1 sites, as signified by S1 = -2.1 mm/s. Magnetic properties change
drastically, the R2 sites start to order magnetically at 25 K, while R1 sites with S1 = -0.9 mm/s are still moving towards Eu
3+. At 4.2 K, the R2 sites exhibit with Bhf = 352 kG (presumably) fm
ordering and induce by their magnetisation fields a magnetic moment at the R1 sites (S1 = -0.2 mm/s) via a Van Vleck mechanism between the 4f-multiplet states of Eu
3+, as indicated by the
observed hyperfine fields (see Fig.2). We will discuss the present results in conjunction with additional information obtained from a
151Eu-Mössbauer study of Eu2-xYxPdSi3, where the
larger Eu2+
ions are substituted by smaller Y3+
ions.
Fig. 1: 151
Eu-Mössbauer spectra of Eu2PdSi3 at 7 GPa and various temperatures. Dashed-doted red sub-spectra belong to the minority R1 sites, dashed blue subspectra to the majority R2 sites.
Fig. 2: Temperature dependence of the magnetic hyperfine fields Bhf at the Eu minority sites (red, dots) and majority sites (blue, squares). Data at 0 GPa are from [1].
[1] R. Mallik, et al., J. Magn. Magn,. Mat. (1998) 185, L135. [2] S. Majumdar, et al, Phys. Rev. B (1999) 60, 6770.
*E-mail : [email protected] Work supported by the DFG, grant WO209/1
309
On the pressure dependence of ordering temperature and magnetization of Y1-xThxCo4B compounds
H. Mayot1,O. Isnard*1, Z. Arnold2, J. Kamarád2 1 Institut Néel CNRS / Université Joseph Fourier, BP166X, F-38042 Grenoble Cédex 9, France
2 Institute of Physics AS CR, v.v.i., Na Slovance 2, 182 21 Praha 8, Czech Republic
Since their discovery, the RCo4B compounds where R represents a lanthanoid have attracted much interest since they present unusually large magnetocrystalline anisotropy [1-4]. Furthermore the isotype RCo4B compounds with non-magnetic R elements such as La, Lu and Y exhibit unique magnetic properties governed by the Co sub-lattice only. Due to the competition between the two inequivalent Co atomic positions a spin reorientation transition and a first order magnetization process (FOMP) have been found in YCo4B compound. More recently ThCo4B isotype compound has been discovered [2], Substituting nonmagnetic Th for Y in YCo4B, volume of the elemental crystal cell increases by 4 % and magnetic properties are remarkably changed, e.g. the Curie temperature TC is lowered by 20 %. and saturation magnetization MS is reduced by more than 40 %. In order to understand more deeper the Co sublattice magnetic properties we present here a results of a study of the both the chemical and hydrostatic pressure effects on magnetic properties along the Y1-xThxCo4B series. Pressure studies were performed on polycrystalline samples under hydrostatic pressure up to 1.1 GPa in magnetic field up to 5 Tesla in a wide temperature range 5 to 340 K. The studies have been performed in a SQUID magnetometer using a miniature CuBe pressure cell. The spin reorientation presented in YCo4B is found to disappear for x<0.2. The first order magnetization process occurs only for Y0.8Th0.2Co4B. The pressure dependence of critical field is analyzed and discussed. A noticeable reduction of TC of all the Y1-xThxCo4B compounds under applying hydrostatic pressure has been observed. The pressure parameter dTC/dP decreases with increasing Th content from -1.1.K/kbar for YCo4B to -0.4 K/kbar for ThCo4B. The MS also decreases with pressure. The unit cell lattice compressibility has been determined from powder neutron diffraction technique in the 0 to 0.5 GPa pressure range. Th for Y substitution is found to reduce significantly the compressibility. The dramatic reduction of TC and MS that arises from negative chemical pressure caused by Th for Y substitution (increase of volume) and qualitatively similar effects - reduction of TC and MS - that arises from hydrostatic (positive) pressure strongly supports an assumption of the dominant effect of valence electrons on the magnetic properties of the substituted Y1-xThxCo4B intermetallics that are connected with the fact that Th and Y do not bring the same amount of valence electrons.
[1] C.V. Thang, P.E. Brommer, N.P. Thuy and J.J.M. Franse, J. Magn. Magn. Mater. 1997, 171 237.
[2] O. Isnard, V. Pop, J.C. Toussaint, J. Phys. Condens. Matter. 2003, 15, 791-801 [3] H. Mayot, O. Isnard, Z. Arnold, J. Kamarad, J. Phys. Condens. Matter 2008, 20, 135207 [4] Z. Arnold, J. Kamarad, Y. Skorokhod, N.M. Hong, N.P. Thuy and C.V. Thang, J. Magn. Magn.
Mater. 2003, 262, 382.
*E-mail : [email protected] Intermetallic compounds, Magnetic properties, Nano-crystalline materials, borides
310
Pressure effect on magnetic properties of Y3Fe62B14 phase in its amorphous and nano-crystalline states
Z. Arnold1, H. Mayot2,O. Isnard*2, C.V. Colin2, J. Kamarád1 1 Institute of Physics AS CR, v.v.i., Na Slovance 2, 182 21 Praha 8, Czech Republic
2 Institut Néel CNRS / Université Joseph Fourier, BP166X, F-38042 Grenoble Cédex 9, France
The nano-crystalline phase of Y3Fe62B14 has been prepared by annealing of amorphous melt-spun ribbon. The cubic crystal structure, space group Im3m, was confirmed by X-ray thermo-diffractions above the crystallization temperature 900 K. The Invar-like effect has been revealed by neutron diffraction experiments at 4 K, the lattice constant a = 1.2359 nm, and at 300 K, a = 1.2357 nm. Previous study showed that both the amorphous and the crystalline phases of this magnetically soft compound exhibit the same average Fe magnetic moment of 1.9 μB and Curie temperature of 510 K *1+. The aim of this study is to contribute to an understanding of the negligible effect of crystallization of Y3Fe62B14 on its magnetic properties, including the Invar-like effect. Magnetization measurements have been carried out in temperature range 5 – 300 K in magnetic field up to 5 Tesla under hydrostatic pressures up to 10 kbar. Magnetization decreases with increasing pressure and the temperature dependence of magnetization and its pressure derivatives are only slightly different for the as spun and the nano-crystalline samples. The values of logarithmic derivative dlnMS/dP are nearly of one order of magnitude higher than that of pure bcc iron, but, much lower than in the case of Invar. Remarkably higher values of dlnMS/dP at 300 K than that at 10 K, see Fig. 1, indicate also pressure induced decrease of the Curie temperature. The obtained results point to unimportant changes in a short range order in Y3Fe62B14 during its crystallization. They also confirm that the similarity of the short range order in Y3Fe62B14 with ThMn12 crystal structure plays important role in volume instability of its magnetic properties [2].
Figure 1: (a) Magnetic isotherms for as spun sample measured at different pressures, (b) temperature dependence of d ln MS / d P of nano-crystalline sample.
[1] D.B. de Mooij, J. L. C. Daams and K. H. J. Buschow, Philips J. Res, 1986, 42, 400-409 [2] Z.Arnold et al., in Proc. of 11th Int. Symposium on Magnetic Anisotropy and Coercivity in
Rare Earth Transition Metal Alloys, Japan, Sendai 2000 , S35
*E-mail : [email protected] Intermetallic compounds, Magnetic properties, Nano-crystalline materials
311
Equal-channel multi-angle pressing effect on structure and functional properties of NbTi alloy
V. Beloshenko1, N. Matrosov1, T. Konstantinova1, V. Spuskanyuk1, V. Chishko1, D. Gajda2, V. Dyakonov1,3*
1A.A. Galkin Donetsk Institute for Physics and Engineering, National Academy of Sciences, 83114 Donetsk, R.Luxemburg str. 72, Ukraine
2International Laboratory of High Magnetic Fields and Low Temperatures, ul. Gajowicka 95, 53-421 Wroclaw, Poland
3Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland
A new version of the equal-channel multi-angle pressing (ECMAP) is proposed. The characteristic property of ECMAP process is extruding the billet through the die channel by the fluid pressure. The proposed novel ECMAP technology allows for processing of much longer billets as the friction influence is dramatically reduced as a result of reduction of the relative extent of the billet-die contact. ECMAP was performed by pressing the billet through a three-angle deforming system of four intersecting channels of equal cross section with half-
angles of intersection of 80, 70 and 80.
Influence of the equal-channel multi-angle pressing (ECMAP) combined with hydroextrusion on structure and functional properties of both bulk samples of Nb+60 at.% Ti alloy and NbTi-based superconducting wires has been studied. The results obtained show that this method is effective for nanostructuration of the NbTi alloy.
The ECMAP method allows to increase the degree of deformation of the alloy preserving the initial dimensions of billets during the plastic deformation. A formation of highly dispersed and homogeneous nanocrystalline structure with uniform distribution of secondary α-NbTi phase in the whole volume as a result of ECMAP treatment improves the mechanical and transport properties of the alloy.
The critical current density of the wire samples (up to 200 mm in length and 0.3 mm in diameter) was measured at temperature of 4.2 K in a transverse external magnetic fields up to 12 T. It is found that the combined deformation with application of the ECMAP method can increase the critical current density in the wire samples by factor of 2 in comparison with the values obtained for the samples produced without ECMAP treatment. The relationship between the character of structural inhomogeneities and the pinning force is estimated. The pinning efficiency is related to the nanostructural state of the alloy. The current-carrying capacity of superconducting NbTi wire is found to increase as a result of pressing process almost by one order of magnitude in low fields and is approximately three times higher in high fields.
This work was a part financed by Minister Nauki i Szkolnictwa Wyzszego (Poland) (Grant N N508 392 035)
312
Effect of internal pressure on structure and magnetism in La1-xRExMnO3 manganites
W. Bażela*1, V. Dyakonov2,3, E. Zubov3, Z. Kravchenko3, A. Szytuła4, N. Stüsser5, H. Szymczak2
1Institute of Physics, Cracow University of Technology, Podchorążych 1, 30-084 Kraków, Poland
2Institute of Physics, PAS, 02-668 Warsaw, Poland 3A. A. Galkin Donetsk Physico-Technical Institute, 340114, Donetsk, Ukraine
4M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków, Poland
5BENSC, Hahn-Meitner Institute, Glienicker Strasse 100, D-14109 Berlin-Wannsee, Germany,
The effect of internal pressure on structure and magnetism in La1-xRExMnO3 manganites (RE = Pr, Nd; x = 0 – 1.0) has been studied by varying the ionic radius, <rRE>, of the A site cations as a result of RE
3+ substitution for La
3+ (the ionic radii for Nd
3+, Pr
3+ and La
3+ are equal to 0.995,
1.013 and 1.061 Å, respectively). X-ray diffraction and magnetic properties measurements have been performed over a wide range of temperature (1.5 – 300 K) and magnetic field (up to 1.5 T).
According to X-ray diffraction data, the crystalline structure under internal pressure evolves across the three crystallographic regions with decreasing <rRE>.
The compounds with x < 0.1 have a rhomboherdral crystalline structure (space group R3 c). The samples with 0.1 < x < 0.5 (in La1-xNdxMnO3) and 0.1 < x < 0.7 (in La1-xPrxMnO3) crystallize in the orthorhombic (space group Pm3m) with a small Jahn-Teller distortion crystal structure (pseudocubic O
' phase). The latter in La1-xNdxMnO3 manganites with x = 0.5 – 0.8 transforms
towards highly distorted orthorhombic phase O'' (space group Pbnm) with the lattice
parameters of c0 /2 < a0 < b0. The samples with 0.9 ≤ x crystallize in monoclinic phase (P21/c).
In La1-xPrxMnO3 manganites with x = 0.7 – 1.0, the pseudocubic O' phase transforms towards
highly distorted orthorhombic phase. Using the lattice parameters values the interatomic Mn – Mn and Mn – O distances and Mn – O – Mn bond angles as a function of <rRE> were calculated. The Mn – O– Mn bonding angles are less than 180
o implying strong distortion of
the MnO6 octahedra.
According to the magnetic and neutron powder diffraction data, a suppression of ferromagnetic-like (FM) behavior in La1-xRExMnO3+δ manganites induced by crystalline lattice deformations has been found. The magnetic ordering strongly evolves with decreasing <rRE>. Three magnetic phases were established, namely, paramagnetic phase (above TC); ferromagnetic state dominates for x < 0.4 in temperature interval from TC to TCANT and at last the phase with a canted spin arrangement below TCANT. For x = 0.4 - 0.6 (when pseudocubic O
'
transforms towards orthorhombic phase O''), the ferromagnetism is no longer dominating
state at low temperatures. A magnetic behavior observed results from the competition between FM double-exchange and AFM superexchange caused by strong lattice deformation effect due to decrease of the average A-site cation radius <rRE> and through modifications of the Mn-Mn distance and the Mn-O-Mn angle.
*E-mail : [email protected] Keywords: internal pressure, crystal structure, magnetic properties, manganites
313
Pressure-induced magnetic and structural transition in the FeCo alloy
R. Torchio*12, S. Pascarelli2, G. Acquilanti2,3, and C. Strohm2
1 Dipartemento di Fisica, Universita di ‘Roma Tre’, Via della Vasca Navale 84, 00146 Rome, Italy
2 ESRF, BP 220, 38043 Grenoble, France 3 Sincrotrone Trieste S.S. 14 km 163, 5 Area Science Park 34149 Basovizza Trieste, Italy
The different electronic structure in Co and Fe is responsible for their different magnetic behavior as well as for the different crystallographic structures at ambient conditions. In Co, the 3d majority bands are completely occupied whereas the 3d minority bands are partially empty, leading to strong ferromagnetism. In Fe both bands are partially empty, and Fe is classified as a weak ferromagnet. At ambient conditions, Fe and Co are both ferromagnetic but crystallize in the bcc and hcp phase respectively. Above 13 GPa, the ferromagnetic bcc Fe phase becomes unstable towards a non-ferromagnetic hcp phase. On the other hand, ferromagnetic hcp Co has been found to be very stable upon compression up to very high pressures.
When Co is added to bcc Fe, the bcc phase persists up to 75 at % of Co at ambient T[1]. Addition of Co stabilizes the ferromagnetic bcc phase with respect to the non-ferromagnetic hcp phase, since higher pressures are required to induce the bcc-hcp transition[2] . Evidently, long range ferromagnetic order appears in hcp Fe1-xCox as x is increased from 0 to 1, but how and why this occurs remains unclear. In particular, no investigation of the magnetic nature of hcp Fe1-xCox (0 < x < 1) has been reported. K-edge X-ray Absorption Near Edge Spectroscopy (XANES) and X-ray Magnetic Circular Dichroism (XMCD), have shown to be very useful in probing simultaneously the structural, electronic and magnetic properties of transition metals at high pressure[3,4]. We present here recent Co K-edge XMCD and XANES results on the 50:50 FeCo alloy. The bcc to hcp phase transition has been observed starting at around 36 GPa – as predicted in previous dynamic techniques[5] and X-ray diffraction[2] works – but is still not complete at 42 GPa (maximum pressure reached in this study). The structural phase transition is accompanied with the progressive and almost total disappearance of the ordered magnetic moment. When pressure is decreased to 27 GPa, the data show that the hpc - non ferromagnetic phase is still dominant, revealing that the structural-magnetic pressure-induced transition is characterized by a large hysteresis. The bcc-ferromagnetic phase is restored at 14 GPa.
[1] S. Pizzini et al.., Phys Rev. B50, 6 (1993) [2] D. Papantonis, W.A. Basset, J. Appl. Phys. 48, 8 (1997) [3] O. Mathon et al., PRL 93, 255503 (2004) [4] V. Iota et al., Appl. Phys. Lett. 90, 042505 (2007) [5] T.R. Loree et al. , J. Appl. Phys. 37, 1918 (1966)
*Email: [email protected] Keywords: FeCo, High Pressure, XMCD, XANES
314
Low temperature conductivity of NbS3 at pressure induced metal-insulator transition.
E.M. Dizhur1 *, A N Voronovskii1, I.E. Kostyleva1, S.V. Zaitsev-Zotov2 1 Institute for High Pressure Physics of the RAS, Russia
2 Institute of Radioengineering and Electronics of the RAS, Moscow, Russia
We report the results of our recent experimental studies concerned with electron systems of quasi-1D “insulator” crystals NbS3 the conductivity of which may be toggled between metallic and insulating regimes as a result of high pressure application.
The quasi-one-dimensional (1D) conductor NbS3 is a member of the family of transition metal trichalcogenides with the general formula MX3, where M = Nb or Ta and X = chalkogen (S or Se for the present study). The materials belonging to this group are strongly anisotropic three dimensional conductors that consist of conducting chains weakly coupled by van der Waals interaction.
Applying a pressure of 6 GPa to NbS3 whiskers led to decrease in room temperature conductivity by more than five orders of magnitude and causes the temperature resistance coefficient to change its sign
[1]. Another observed feature is a jump in the resistance versus
temperature curve, which reminds of the Peierls transition with temperature linearly depending on pressure. This result supported the current understanding that impurities in 1D chains form tunnel barriers that break the chains into segments and that a Luttinger-liquid state can exist if the electron hopping integral between the chains is smaller than the dimensional quantization energy in the chain segments between the impurities. Making the chains closer to each other under pressure causes the transition to 3D behavior.
The samples under study were NbS3 whiskers of the highest resistivity polytype (I) that was 80 Ωcm at room temperature.
4-probe resistance measurements were carried out during the natural warm up of the 'toroid' type apparatus previously cooled down to helium temperatures. Current-voltage characteristics obtained in a current sweep revealed a differential resistance growth at small currents quickly being smoothed with temperature above 50 K.
We acknowledge financial support by RFBR, Program ”Physics of compressed matter” of the Presidium of RAS, the Presidential Program of leading scientific schools support.
[1] E. Dizhur, M. Il’ina, S. Zaitsev-Zotov, Assumed Peierls Transition in NbS3 under Pressure. phys. stat. sol. phys. stat. sol. (b), 1– 4 (2008)
*E-mail : [email protected] Key words: one-dimensional system, Peierls transition, metal–insulator transition, high pressure
315
Direct observation of the antiferrodistorsive phase of SrTiO3
at high pressure and room temperature
J.P. Itié*1, A.M. Flank1, P. Lagarde1, S. Ravy1 and A. Polian2 1Synchrotron SOLEIL, St Aubin, France
2 IMPMC, Paris, France
The phase transitions of SrTiO3 under pressure have been studied both by single crystal x-ray diffraction and by x-ray absorption spectroscopy at the Ti K edge single crystals and on powdered samples. The first phase transformation is observed above 6 GPa and is related to the antiferrodistorsive structure observed at room pressure and low temperature. The superstructure x-ray reflections are observed in the XRD pattern (figure 1) and can be indexed in the pseudo-cubic structure as the (3/2,1/2,1/2) reflection (figure 2). At the transition a modification of the preedge features of the absorption spectrum is observed and can be interpreted as a centering of the Ti atom with respect to the oxygen octahedron.
At higher pressure a new transformation occurs, leading to strong modifications in the absorption spectrum while the diffraction image looks quite similar.
* E-mail : [email protected] Keywords: Perovskites, diffraction, X-ray absorption, phase transition
Figure 1: zoom of the X-ray diffraction of SrTiO3 at 8.6 GPa
Figure 2: integration of the image 1
316
Phase transitions of Fe under high pressure
A. Monza1,2, M. D’Astuto2, A. Shukla2, J. P. Rueff1, O. Mathon3, S. Pascarelli3, G. Monaco3, S. Huotari3, F. Baudelet1
1Soleil, L’orme des merisiers St-Aubin, BP 48, 91192 Gif-sur-Yvette France 2Institut de Minéralogie et de Physique des Milieux Condensés,
140 rue de Lourmel, 75015 Paris 3ESRF, Av. des Martyrs, 38000 Grenoble
Iron is the subject of abundant studies aiming at revealing its properties under high-pressure (HP) and high-temperature (HT) conditions. The knowledge of the Fe phase diagram serves as a model-system for the theoretical understanding of 3d electronic properties and is also of importance for geophysics. The α-ε transition in Fe is extensively studied (Fig.). The structural transition is accompanied by a ferromagnetic to non magnetic transition. A recurrent question concerns the driving mechanism of this transition: phonon softening or magnetic moment collapse [1].
Recently, it has also been reported [2] that a superconducting phase appears at low temperature under pressure. The origin of this superconducting phase is still a subject of debate. Nevertheless, some DFT calculations [3] predict the apparition of incommensurate antiferromagnetic spin fluctuations, which could explicate this superconducting phase.
Results of XANES-EXAFS-XMCD (on ID24-ESRF) and X-rays inelastic scattering (on ID16-ESRF) will be presented.
Combination of XANES-EXAFS-XMCD gives us simultaneously information on both the structure and the magnetic state of Fe. We have studied the structural and magnetic properties of Fe by rising and decreasing pressure at room temperature. Our data seems to indicate that phase transformation between bcc and hcp pass through an intermediate phase, which is magnetic.
X-rays inelastic scattering is a good alternative to Mössbauer to probe the local magnetic electrons of atoms [4]. By studying the Fe-Kβ fluorescence line, we have seen that there is almost no difference between spectra at room temperature and spectra at 11.5 K, which hampers to detect the presence of an antiferromagnetic phase above 15 GPa.
*1+ O. Mathon, F. Baudelet, J. P. Itié, A. Polian, M. D’Astuto, J.C. Chervin, S. Pascarelli, Phys. Rev. Lett. 2004, 93, 255503.
[2] K. Shimizu. T. Kimura, S. Furomoto, K. Takeda, K. Kontani, Y. Onuki, K. Amaya, lett. to nature 2001, 412, 316.
[3] V. Thakor, J. B. Staunton, J. Poulter, S. Ostanin, B. Ginatempo, E. Bruno, Phys. Rev. B 2003, 67, 180405.
[4] J. P. Rueff, M. Krisch, Q. Cai, A. Kaprolat, M. Hanfland, M. Lorenzen, C. Masciovecchio, R. Verbeni, F. Sette, Phys. Rev. B 1999, 60, 14510.
E-mail : [email protected] High Pressure, XMCD, phase transitions, inelastic X-rays scattering
Figure 1: Phase transitions diagram of Fe in pressure and temperature
317
Structural and magnetic phase transitions in the complex perovskite systems BiMn7O12 and LaMn7O12
G. Rousse1, F. Mezzadri4, G. Calestani4, E. Gilioli3, M. Calicchio3, F. Bolzoni3, R. Cabassi3, G. André2, F. Bourée2, P. Bordet5, M. Marezio6 and A. Gauzzi1
1Institut de Minéralogie et de Pysique des Milieux Condensés, Université Pierre et Marie Curie and CNRS, 75005 Paris, France
2Laboratoire Léon Brillouin, CEA-CNRS, 91191 Gif-sur-Yvette, France 3Istituto Materiali Speciali per Elettronica e Magnetismo,
Consiglio Nazionale delle Ricerche, 43100 Parma, Italy 4Dipartimento di Chimica GIAF, Universitá di Parma, 43100 Parma, Italy
5Institut Néel-CNRS, 38042 Grenoble Cedex 9, France 6CRETA-CNRS, 38042 Grenoble Cedex 9, France
By means of neutron powder diffraction as a function of temperature, we have investigated the nuclear and magnetic structures of the new systems (BiMn
3+3)(Mn
3+4)O12 and
(LaMn3+
3)(Mn3+
4)O12. Single-phase powder samples of both phases were recently synthesized under high pressures at the IMEM-CNR in Parma. In both systems, the A’ cation is trivalent, thus all of the Mn B-cations are expected to be trivalent.
Both systems crystallize in the A’A3B4O12 complex perovskite structure consisting of a pseudo-cubic network of corner-shared BO6 octahedra. This system may display a rich manyfold of charge, spin and orbital orderings characteristic of mixed-valence systems.
In both systems, we have determined precisely the nuclear and magnetic structures as a function of temperature, between room temperature and 2 K. We have observed two magnetic transitions at low temperature in the La compound, involving crystallographically different Mn ions. Between 65K and 20K, the propagation vector k is (0,0,0), and only the Mn ions in the B-site are ordered. Below 20K, additional magnetic reflections appear, the lattice is no longer body centered, and magnetic moments of manganese atoms belonging to the A site are ordered. The magnetic structure has been solved by simulated annealing techniques, with help of symmetry analysis. It will be discussed in comparison with the Na analog which had been studied before. For the Bi compound, the effect of the lone pair of Bi on the structure will be discussed, as well as the magnetic structures observed at low temperature.
*Email: Keywords:
318
Intercalation- and Pressure- Driven Stabilization of Superconductivity in 1T-TaS2
A. Sellam*1, M. D’Astuto1, E. Gilioli2, Y. Le Godec1, G. Rousse1, S. Carlsson1, D. Taverna1, G. Loupias1, A. Shukla, and A. Gauzzi1
1- Institut de Minéralogie et de Physique des Milieux condensés, Université Pierre et Marie Curie and CNRS, Paris, France
2- Istituto Materiali per Elettronica Magnetismo, CNR, Parma, Italy
In spite of intense research efforts, the issue of the competition between charge density wave (CDW) and superconductivity (SC) in Layered Transition Metal Dichalcogenides (LTMD) remains controversial. Recently, it has been reported that both chemical intercalation [1] and pressure [2] tend to suppress CDW, thus stabilizing SC. In order to elucidate this point, in this work we have attempted to unveil the structural changes induced by intercalation and pressure that may be relevant to the stability of the SC state. We have studied the structural and magnetic properties of new intercalated 1T-AxTaS2 compounds (A transition metal or post-transition metal) synthesized under high-pressure using a Paris-Edinburgh press [3]. Our results show that a 1% shrinking of the 1T-TaS2 unit cell volume completely suppresses the CDW instability and stabilizes superconductivity with Tc≈3 K. In addition, we find that chemical intercalation merely enhances Tc up to ≈4 K and Tc is almost insensitive to the intercalant concentration, x. Our data analysis suggests that the onset of superconductivity is primarily associated with the regularization of the TaS6 octahedra, whilst the effect of dimensionality of the electronic states is negligible.
Crystal structure of pristine 1T-TaS2
[1] E. Morosan, H. W. Zandbergen, B. S. Dennis, J. W. G. Bos, Y. Onose, T. Klimczuk, A. P. Ramirez, N. P. Ong and R. J. Cava, Nature Physics 2006, 2, 544.
*2+ B. Sipos, A. F. Kusmartseva, A. Akrap, H. Berger, L. Forró and E. Tutiš, Nature Materials 2008, 7, 960.
[3] J.M. Besson, R.J. Nehnes, G. Hamel, J.S. Loveday, G. Weill, S. Hull, Physica B 1992, 180-181, 907.
*Email: [email protected] Keywords: charge density wave, superconductivity, transition metal dichalcogenides, pressure
319
Solvothermal Processes
Lectures Solvothermal crystal growth : Elaboration of ZnO single crystals. _________________ 321
Re-crystallization and Micronization of Pharmaceutical Compounds by Applying
the Supercritical Fluid Technology____________________________________ 322
Reaction of 2-Methoxyethanol in Sub- and Supercritical Water ___________________ 323
How CO2 induces asphaltene flocculation at high pressure: an experimental
investigation _____________________________________________________ 324
Posters SP 01 : Cavitation features of liquids near melting point. ________________________ 325
SP 02 : Solvothermal Processes: role of different key-factors on the reaction
mechanisms _____________________________________________________ 326
SP 03 : Hydrothermal Crystal Growth of Si(1-x)GexO2: Objectives and main
requirements _____________________________________________________ 327
SP 04 : Composition of essential oil of Artemisia dracunculus L. (tarragon) from
Kazakhstan obtained by supercritical CO2 extraction ____________________ 328
320
321
Solvothermal crystal growth : Elaboration of ZnO single crystals.
A. Largeteau, S. Darracq, G. Demazeau
CNRS, Université de Bordeaux, ICMCB, site de l’ENSCPB, 87 avenue du Dr. A. Schweitzer, 33608 PESSAC Cedex (France)
The preparation of single crystals of functional materials is an important challenge for developing different applications in electronics, opto-electronics, spintronics…
Solvothermal crystal growth is characterized by the use of a specific solvent (aqueous ou nonaqueous) able in an appropriated combination of temperature and pressure conditions to improve the dissolution of a nutrient.
A gradient of temperature (ΔT) is applied between the dissolution zone (nutrient) and the crystallization zone (seeds) for inducing the transportation of the solvated chemical species. Such a ΔT value can be negative or positive versus the nature of the solubility (normal or inverse).
Solvothermal crystal growth processes being characterized by mild temperature conditions, consequently such processes have been firstly developed for preparing α-quartz single crystals using different aqueous solutions.
During these last ten years such processes have been investigated for different functional materials as GaN [1-4] or ZnO[5-8] .For these materials different crystal growth processes have been investigated but the solvothermal process is very often preferred due to the small density of defects characterizing the resulting single crystals.
This scientific contribution presents the state of the art concerning the solvothermal crystal growth of ZnO and the main problems to be solved in the near future.
[1] A. Denis, G. Goglio, G. Demazeau, Materials Science & Engineering R, 2006, 50, 167 [2] B. Wang, M.J. Callahan, J. Crystal Growth, 2006, 291, 455 [3] T. Fukuda, D. Ehrentraut, J.Crystal Growth, 2007,305, 304 [4] T.Hashimoto, F.Wu, J.S. Speck, S. Nakamura, J. Crystal Growth, 2008, 310, 3907 [5] T. Sekiguchi, S. Miyashita, K. Obara, T. Shishido, N. Sakagami, J. Crystal
Growth,2000,214,72 [6] K. Maeda, M. Sato, I. Niikura, T. Fukuda, Semicond.Sci. Technology, 2005, 20, S49 [7] G. Dhanaraj, M. Dudley, D. Bliss, M. Callahan, M. Harris, J. Crystal Growth, 2006, 297, 74 *8+ L.N. Dem’yanets, V.I. Lyutin, J. Crystal Growth, 2008,310, 993
*E-mail : [email protected] Keywords : Solvothermal Crystal growth process, ZnO,
322
Re-crystallization and micronization of pharmaceutical compounds by applying the supercritical fluid technology
Y.-P. Chen*
Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan
Supercritical fluid technology has been widely applied for various fields including extraction, reaction, preparation of nanomaterials [1], green chemical synthesis and processing of semiconductors. The supercritical technology has also been employed for producing the re-crystallized and micronized pharmaceutical particles [2-4]. The micronized pharmaceutical compounds generally present improved dissolution rate. This process is also feasible in screening new polymorphism of valuable products.
This study presents our recent results for the pharmaceutical compounds using either the supercritical anti-solvent (SAS) or the rapid expansion of supercritical solution (RESS) process. The high pressure experimental equipments included three sections of carbon dioxide supply, solution supply, and the precipitator. Particle morphology and crystallinity were examined by SEM and XRD, respectively. Particle size and its distributions were determined using image analysis software Image-J. Taking the active pharmaceutical ingredient of SMZ (Sulfamethoxazole) as an example, the mean particle size was reduced to one tenth of its original value after the continuous SAS process. The dissolution rate of the micronized SMZ was enhanced by 2.5 times [5]. Another example is the micronization of the non-steroid anti-inflammatory drug, nabumetone, using the RESS process. The particle size was again significantly reduced, and a dissimilar dissolution behavior was observed for the micronized product.
[1] E. Reverchon, R. Adami, J. Supercrit. Fluids, 2006, 37, 1. [2] M. Bahrami, S. Ranjbarian, J. Supercrit. Fluids, 2007,40, 263. [3] M. Perrut, J. Y. Clavier, Ind. Eng. Chem. Res., 2003, 42, 6375. [4] I. Pasquali, R. Bettini, F. Giordano, Eur. J. Pharm. Sci., 2006, 27, 299. [5] Y. P. Chang, M. Tang, Y. P.Chen, J. Materials Sci., 2008, 43, 2328.
*E-mail: [email protected] Keywords: supercritical, pharmaceutical, micronization
323
Reaction of 2-methoxyethanol in sub- and supercritical water
H. Makida, Y. Uosaki*
Department of Chemical Science and Technology, Faculty of Engineering, University of Tokushima, 2-1 Minamijosanjima-cho, Tokushima 770-8506, Japan
Decomposition of organic wastes in sub- and supercritical water is one of the innovative technologies for recovery of starting or useful materials from used plastics. In this work, the decomposition of 2-methoxyethanol in water was studied over the temperature range of 473-723 K at an interval of 50 K under the pressure of 30 MPa. Since 2-methoxyethanol has both an ether linkage and a hydroxyl group, it can be considered that the reaction proceeds as follows:
CH3OC2H5OH + H2O -> CH3OH + HOCH2CH2OH
Reactions were conducted in a tubular flow reactor system, details of which have been described previously[1]. The reactor made of Inconel 600, of which internal volume is 12 cm
3,
was maintained at the required operating temperature with the aid of a high-temperature thermostat (Isuzu, SLK-11S). Residence times were controlled between 144 and 2160 s. Aqueous solutions containing 5 mass% of 2-aminoethanol were prepared with degassed highpurity water, and reserved in a glass vessel filled with N2 gas; the vessel was cooled in an icewater bath to prevent the hydrolysis of 2-methoxyethanol at ambient conditions. The feed solutions under stirring were pumped into the reactor by a HPLC pump. The solutions discharged from the reactor were analyzed by use of a gas chromatograph (Shimadzu, Model GC-8PT).
At 473 K and 523 K, the formation of methanol and ethylene glycol was not detected even at the residence time of 2160 s, but both compounds were formed at the temperature of 573 K and above. At 573 K, the concentration of 2-methoxyethanol decreased, while that of methanol increased with the residence time and the sum of the concentrations of both compounds was almost equal to the initial concentration of 2-methoxyethanol; the mass balance of 2-methoxyethanol held well at 573 K. Similar results were obtained even at 623 K. However, since only 10% of 2-methoxyethanol was decomposed at 573 K and the residence time of 2160 s, higher temperature is required to attain a higher conversion of 2-methoxyethanol. The decomposition of 2-methoxyethanol increased with an increase in temperature. At 723 K, about 95% of 2-methoxyethanol was decomposed at 2160 s; the concentration of methanol showed a maximum at ca. 720 s and gas formation was observed. Quantitative analysis of gases revealed that CH4, C2H6, H2, CO2, and CO were formed; these gases are derived from methanol and ethylene glycol.
High temperature is needed to decompose 2-methoxyethanol in water in a short time, but the temperature range of 573-623 K is preferred in order to recover methanol and ethylene glycol effectively.
[1] T. Moriyoshi, K. Sakai, Y. Uosaki, High Pressure Research, 2001, 20, 491.
*E-mail : [email protected] Keywords: subcritical; supercritical; 2-methoxyethanol; water
324
How CO2 induces asphaltene flocculation at high pressure: an experimental investigation
H. Carrier1, H. Labrador1,2 and JL Daridon1 1Laboratoire des Fluides Complexes, UMR 5150, Université de Pau et des Pays de l´Adour, France.
2Laboratorio de Petróleo Hidrocarburo y Derivados, Universiad de Carabobo, Venezuela
Many operational troubles due to asphaltenes in crude oils are reported in the open literature: rock reservoir plugging, deposits formation in production wells (generally around the depths corresponding to the bubble point) or appearing during the transportation and the treatment of fluids from different origins (i.e. having different compositions). Asphaltenes are still defined today as a solubility class, which illustrates the fundamental questioning that persists on their exact nature (size, molar mass, composition, molecular arrangement) and the laws which govern their behavior, phenomena of aggregation and flocculation in particular.
In fact, although numerous research teams are involved in such area and a lot of work has been done during the last decades, the effects of pressure, temperature or composition remain poorly defined.
With the objective to improve the knowledge in this research area, the laboratory of Complex Fluids, UMR 5150, has developed an original experimental setup allowing to detect the asphaltene flocculation threshold in the pressure range 1-70 MPa for temperatures ranging from 25 to 200°C. The device is organized around two high pressure mobile piston cells necessary to re-combine, in pre-defined proportions, dead oil with natural gases. The setup allows to measure interface properties as well as bulk ones. In particular, the state of aggregation of asphaltenes is detected by a high-pressure filtration process using filters of porosity of 0.5 μm.
Focusing on deposits related to improved oil recovery or gas storage, we reproduced a pressure drop, at constant temperature, similar to the one occurring in a production pipe. Experimental device as well as the observed effects on two fluids containing a large amount of CO2 are presented. The obtained results establish the capacities of the device to bring fundamental information on the behavior of these complex multi-component systems.
*Email : [email protected] Keywords : asphaltenes, CO2, flocculation, pressure
325
Cavitation features of liquids near melting point.
V.A. Sosikov*, A.V. Utkin
Institute of Problems of Chemical Physics Russian Academy of Science, Chernogolovka Russian Federation.
According to theoretical concepts, liquids can endure high tensile stresses of up to 0.1–1 GPa [1]. It is assumed that discontinuity of the material results from void formation by a homogeneous nucleation mechanism.
In this work the influences of strain rate on the negative pressure have been investigated in liquids near melting point by the example of water, hexadecane and pentadecane. Paraffin was investigated in solid and liquid phase. The method of spall strength measurements was applied and wave profiles were registered by laser interferometer VISAR [2].
The most interesting finding is that in our experiments with water the isentrope can cross the melting curve at a negative pressure. When this is the case, the resulting state of water is in the double metastable region where it is superheated with respect to the liquid–vapour equilibrium and supercooled with respect to ice.
The process of destruction in hexadecane is double staged. At the first stage formation of cavities starts, at the second stage the cavity grow rate increases and the spall pulse occurs. Anomal dependence of the loading pressure on the negative pressure was discovered in pentadecane. While the amplitude of loading pulse increases approximately in 2 times the value of stain rate approximately doubled.
This work was supported by grants of President МК-5153.2008.8 and RFBR 08-02-01189-а
[1]. Ya. B. Zel'dovich, Zh. Eksp. Teor. Fiz., 12, Nos. 11/12,525-538 (1942). [2]. G. I. Kanel', S. V. Razorenov, A. V. Utkin, and V. E. Fortov, Shock-Wave Phenomena in
Condensed Media [in Russian], Yanus-K, Moscow (1996).
*Email : [email protected]
326
Solvothermal processes: role of different key-factors on the reaction mechanisms
G. Demazeau
CNRS, Université de Bordeaux, ICMCB, site de l’ENSCPB, 87 avenue du Dr. A. Schweitzer, 33608 PESSAC cedex (France)
Solvothermal processes can be described chemical reactions in a close system involving different precursors in the presence of a solvent (aqueous or non aqueous) at a temperature at least higher than its boiling temperature. Consequently pressure is involved (imposed or autogeneous pressure). The system can be in sub- or supercritical conditions, homogeneous or heterogeneous.
Solvothermal processes are governed by different key-factors, as in particular:
-the nature of the solvent,
-the composition and sometime the structure of the reactants,
-the additives,
-the thermodynamical conditions (temperature and pressure).
The main objective of Solvothermal Processes is to control, through the optimization of these different key-factors, the reaction mechanisms leading to the target product (novel material, hybrid material, nanocrystallites well defined in size and morphology, nano-structured thin films….)
This contribution will describe, through different examples, the impact of these key-factors for managing the reaction mechanisms.
*E-mail : [email protected] Keywords : Solvothermal processes, key-factors governing reaction mechanisms, impact of these factors.
327
Hydrothermal crystal growth of Si(1-x)GexO2: objectives and main requirements
A. Largeteau1*, S. Darracq1, G. Demazeau1, V. Ranieri2 and O. Cambon2 1CNRS, University Bordeaux, ICMCB site ENSCPB,
87 Av. Dr Schweitzer, Pessac, F-33608, France 2Institut Charles Gerhardt de Montpellier, UMR5253, Université Montpellier II,
Place E. Bataillon, F-34095 Montpellier, France
Till now, α-quartz single crystal is the most used piezoelectric material as frequency filters and resonators due to its frequency stability.
In the α-quartz type materials (MIV
O2 or MIII
XVO4), important structure-property relationships
have been established between thermal stability, physical and piezoelectric properties and structural distortion with respect to the α-quartz structure type [1-3]. Based on these results the increase of the quartz lattice distortion by substituting Si
4+ by Ge
4+ was proposed in order
to improve the piezoelectric coupling coefficient.
This study involves the experimental investigations of a reproductive crystal growth process of Si(1-x)GexO2 (x<0.30) with α-quartz structure, performed under hydrothermal conditions. The effects of hydrothermal crystal growth parameters: solvent composition, nature of the nutrient, temperature, pressure and temperature gradient has been evaluated.
The germanium content and its repartition into the single crystals have been characterized by electron microprobe analysis.
In addition, a specific attention has been focused on the role of pressure parameter on the formation of secondary phases (germanates) and the density of defects characterizing the Si(1 - x)GexO2 single crystal.
[1] Haines J, Cambon O, Philippot E, Chapon L and Hull S, 2002, J. Solid State Chem. 166, p 434-441.
[2] Cambon, O.; Yot, P.; Rul, S.; Haines, J.; Philippot, E. Solid State Sci. 2003, 5, 469. [3] Cambon, O.; Haines, J. Proc. 2003 IEEE Int. Freq. Control Symp. – 17th Eur. Freq. Time
Forum (Piscataway, NJ: IEEE) 2003, 650.
Acknowledgments : Thanks to DGA for the financial support.
*E-mail : [email protected] Keywords: hydrothermal crystal growth, α-quartz- type structure, Ge substitution,
328
CO2 cylinder
Heating chamber
Chiller
Flow meter
Extractor
Back pressure valve
CO2
Water bath
extract
CO2 pump
Composition of essential oil of Artemisia dracunculus L. (tarragon) from Kazakhstan obtained by supercritical CO2 extraction
Y. M. Suleimenov1*, S. Machmudah2, M. Sasaki2, M. Goto2 1 L.N. Gumilyov Eurasian National University, Astana, Kazakhstan
2 Kumamoto University, Kumamoto, Japan
Artemisia dracunculus L. (tarragon) is widely used in folk medicine and the food industry
[1-2]. The
composition of volatile components and constituents of extracts obtained by different solvents from samples grown in various regions of the world is known in the letters
[3-6], however, the
composition of supercritical CO2 extracts from Kazakhstan hasn’t been studied yet.
We have conducted a research of dynamics of A. dracunculus supercritical СО2 extraction, growing in the territory of Kazakhstan Republic and defined the composition of the extract fractions by GC/MS.
Supercritical extraction was carried out at a pressure of 15 МPa, flow rate of CO2 - 3 ml/min and temperature of extractor - 40 ºС. We collected extracted fractions in every 10 min within an hour. The yield of essential oil is 1,01%. The obtained fractions were dissolved in 1 ml of ethanol, cooled overnight at -20 °С and analyzed by GC/MS at Hewlett-Packard device on capillary column HP-5.
It has been established, that the composition of the obtained fractions slightly varies
depending on time. 1.04 to 15.15 % of phytol, 3.33 to 14.69 % of -amirin, and 1.75 to 8.43 % of β-sitosterol were found as main components. Monoterpenoid composition of the extract is
represented by -phellandrene, - and β-pinene, sabinene, 2- and 3-carene, limonene and p-cymol in terms of negligible amount, which differs from A. dracunculus essential oil composition obtained by water distillation from the same region of Kazakhstan
[7].
[1] A. M. Aglarova, I. N. Zilfikarov, O. V. Severtseva, Pharmaceut. Chem. Journal, 2008, 42, 2. [2] A. Y. Leung, S. Foster, Encyclopedia of Common Natural Ingredients. Used in Food, Drugs
and Cosmetics, John Wiley & Sons, Inc, Second edition, 1996, 1-4. [3] M. Curini, F. Epifano, S. Genovese, F. Tammaro, L.Menghini, Chem. Nat. Comp, 2006, 42, 6. *4+ I. B. Ruckih, M. A. Hanina, E. А. Seryh, L. M. Pokrovskii, А. V. Tkachev, Khimiya rastit. Syr’ja,
2000, 3, 65–76. [5] D.M. Ribnicky, A. Poulev, M. Watford, W.T. Cefalu, I. Raskin, Phytomedicine, 2006, 13, 550. [6] Y. Zhang, Y. Zhang, J. Yao, Y. Yang, L. Wang, L. Dong, Zhongguo Zhongyao Zazhi, 2005, 30
(8), 594-596. [7] Ye. M. Suleimenov, G. A. Atazhanova, A. V. Tkachev, S. M. Adekenov, Actual problems of
creation of medicine drugs from natural origins, St. Petersburg, 2003, 377-382.
Keywords: Artemisia dracunculus L., supercritical CO2 extraction, GC/MS
Scheme of supercritical CO2 extraction
329
Chemistry
Lectures High-pressure asymmetric organic synthesis __________________________________ 331
High pressure hydrogen generation and delivery ______________________________ 332
Influence of high explosives initial density on the reaction zone for steady-state
detonation _______________________________________________________ 333
Molecular Dynamics Calculations of Molecular Volumes ________________________ 334
Posters CH 01 : High-pressure study of graphite-like BCx phases _________________________ 335
CH 02 : Implementation of ultrasound velocity measurements at high pressure
to study micellar dynamics _________________________________________ 336
CH 03 : Influence of nitrobenzene concentration on the detonation waves
structure for FEFO/ nitrobenzene solution _____________________________ 337
CH 04 : High-pressure synthesis of FeO–ZnO solid solutions with rock salt
structure ________________________________________________________ 338
CH 05 : Layered cobaltates NaxCoO2 under pressure ____________________________ 339
CH 06 : Molecular Dynamics Calculations of Activation Volumes __________________ 340
CH 07 : In situ EXAFS studies of Ta—N systems at high pressure __________________ 341
CH 08 : High pressure inelastic x-ray studies of nitrogen-containing compounds:
melamine and gallium nitride. ______________________________________ 342
CH 09 : Structural transition of the layered AuCrS2 system under high pressure ______ 343
CH 10 : Pressure-induced polymorphism in 1,4-diazabicyclo[2.2.2]octane
complexes _______________________________________________________ 344
330
331
High-pressure asymmetric organic synthesis
J. Jurczak
Institute of Organic Chemistry, Polish Academy of Sciences, 01-224 Warsaw Faculty of Chemistry, University of Warsaw, 02-093 Warsaw, Poland
The synthesis of chiral compounds in optically pure form is one of the crucial requoirementsof modern organic chemistry. We focused our attention on diastereo- and enantioselective reactions such as [4+2] and 1,3-dipolar cycloadditions, ene, nitroaldol as well as Friedel-Crafts reactions. In the investigations of enentioselective reactions we applied chiral metallosalen complexes and small metal-free molecules as catalysts. All these catalysts are not effective in above-mentioned reactions under thermal conditions owing to their relatively low Lewis acidity, however, this problem can be solved by application of high-pressure technique. The results showing how low-active catalysts under thermal conditions can be successfully applied for reactions accelerated under high-pressure conditions usually with increase of enantioselectivity.
332
High pressure hydrogen generation and delivery
G. Laurenczy
EPFL, École Polytechnique Fédérale de Lausanne, Institut des Sciences et Ingénierie Chimiques, Laboratoire de Chimie Organométallique et Médicinale,
CH-1015 Lausanne, Switzerland
Hydrogen is a valuable industrial material and most probably it will be the energy carrier of the future. The widespread application of hydrogen is currently limited mainly because of storage and delivery problems. A viable high pressure hydrogen generation process – hydrogen storage method has been developed recently, using carbon dioxide as hydrogen vector [1-3]. Formic acid has some advantages over the other storage methods: the pure formic acid is a liquid with a flash point - ignition temperature of + 69 °C, much higher than that of the gasoline (– 40 °C) or ethanol (+ 13 °C); it contains 53 g l
-1 hydrogen at room
temperature and atmospheric pressure, which is twice as much as compressed hydrogen gas can attain at 350 bar pressure, and the 85 % formic acid solution is not any more inflammable.
The catalytic decomposition of HCOOH takes place rapidly, over a large range of pressures (up to 1250 bar), formic acid splitting leads only to gaseous products (H2/CO2).
The reaction is carried out in aqueous solution, the formed high pressure gases were found not to inhibit the decomposition of the formic acid (Figure 1.)
The Swiss National Science Foundation and EPFL are thanked for financial support.
[1] G. Laurenczy, C. Fellay, P. J. Dyson, PCT Int. Appl. (2008), 36pp. CODEN: PIXXD2 WO 2008047312 A1 20080424 AN 2008:502691
[2] C. Fellay, P. J. Dyson, G. Laurenczy, Angew. Chem. Int. Ed., 2008, 47, 3966. [3] C. Fellay, N. Yan, P. J. Dyson, G. Laurenczy, Chem. Eur. J., 2009, 15, 3752.
Email: [email protected]
Figure 1 : Formic acid decomposition kinetics at 120 °C, catalyst: 22.5 mM Ru(II) with 2 eqv. TPPTS.
333
Influence of high explosives initial density on the reaction zone for steady-state detonation
A.V. Utkin*, V.M.Mochalova
Institute of Problems of Chemical Physics RAS, Chernogolovka, Russia
According to the classical theory the detonation wave consists of a shock jump and a chemical reaction zone, in which the pressure decreases and the matter expands, i.e. Von Neumann spike is shaped. However, it was found that in RDX and HMX at high initial density the pressure increases in the reaction zone and spike does not form. Moreover, it is not clear, whether the Chapman-Jouguet state will be reached, and what the selection rule of detonation velocity is in this case. To solve these key theoretical problems the experimental investigation of the reaction zone transformation under initial density increase in pressed RDX (C3H6N6O6), HMX (C4H8N8O8), ZOX (C6H8N10O16, Bis (2, 2, 2 – Trinitroethyl - N - nitro) Ethylenediamine), and TNETB (C6H6N6O14, Trinitroethyl trinitrobutyrate) was conducted.
The laser interferometric system VISAR was used to investigate the detonation waves structure of pressed HE with different initial density. The laser beam reflected from a 100 -
400 m aluminum foil placed between the charge and the water window. As the result of experiment we have the velocity of the foil - water border, which represents all details of the reaction zone structure in detonation wave.
Critical initial densities c at which the reaction zone structure changes crucially were found: Von Neumann spike was recorded if the density was less than the critical value, otherwise
monotone pressure increase in the reaction zone was observed. The c is equal to 1.72 g/cm3,
1.82 g/cm3, 1.56 g/cm
3, and 1.71 g/cm
3 for RDX, HMX, TNETB and ZOX respectively.
The results obtained for RDX and TNETB demonstrate that the c essentially depends on the sample structure and is determined not only by the HE particle size, but also by the pressing process. The abnormal change of particle velocity at critical density was found for RDX and
TNETB: nearly c the velocity does not increase with the increase of initial density. It can be explain by transition to underdriven detonation at the disappearance of Von Neumann spike.
The results of this work confirm the possibility of detonation wave propagation without Von Neumann spike in powerful HE. The reaction zone structure changes qualitatively at the critical initial density. It can be explained by growth of the initial decomposition rate of explosive with increase of density if it is assumed that the physicochemical transformations take place in the compression wave. Moreover when the pressure increases in the reaction zone, the final state of detonation products can be on the weak part of detonation Huhoniot.
* E-mail: [email protected] Keywords: detonation wave, RDX, HMX, ZOX.
334
Molecular dynamics calculations of molecular volumes
N. Boon, P. Dance, L. Thiele, V. Dinh, N .Weinberg*
Department of Chemistry, University of the Fraser Valley, Abbotsford, Canada
Traditionally, the effects of pressure on the reaction rates are expressed in terms of their pressure derivatives, known as volumes of activation. Within the frameworks of the transition state theory, these volumes of activation can be identified with the difference in volumes of transition states and reactants. Since the volumes of reactants are readily available experimentally, the volumes of activation provide a direct measure of the transition state volumes and thus a unique glimpse of these transient species. We propose a new approach toward calculating molecular volumes based on molecular dynamics simulations. The results of calculations agree well with the experimental data.
*Email : [email protected] Keywords: activation volumes, reaction volumes, high pressure reactions, molecular dynamics
335
High-pressure study of graphite-like BCx phases
O. O. Kurakevych, V. L. Solozhenko*
LPMTM-CNRS, Université Paris Nord, F-93430 Villetaneuse, France
Recently, a number of turbostratic graphite-like BCx phases (t-BCx) of different stoichiometry (boron content up to 50 at %) have been synthesized by thermal chemical vapor deposition[1]. These phases became subject to intensive investigation because they may serve as precursors for high pressure – high temperature synthesis of new superhard diamond-like B-C phases [2-4]. In the present work we report the results of systematic study of the high-pressure behavior of t-BCx using X-ray diffraction and Raman scattering.
X-ray diffraction patterns of t-BCx at ambient conditions show broad symmetric lines 001 and 002, and asymmetric two-dimensional reflections 10 and 11 that are typical for turbostratic (completely one-dimensionally disordered) layered structures[5]. The distribution of boron atoms throughout the random layer lattice and the layer structure are not known so far. At ambient conditions the lattice parameters for t–BCx vary from 2.44 to 2.48 Å (a-parameter) and from 3.40 to 3.44 Å (c-parameter) and show a complex dependence on boron content, microstructure and strains. At the same time, the higher is a-parameter, the lower is c-parameter.
In situ X-ray diffraction with synchrotron radiation has been used to study equations of state of t-BCx phases up to 35 GPa. It has been found that the bulk moduli vary from 17 to 30 GPa, while the axis moduli show the non-monotone dependence on boron content and strong correlation with corresponding lattice parameters. The buckling of graphite-like layers[6], their coupling (the onset of correlations in the stacking order[7]), the abrupt change in interlayer spacings[6] between certain pairs of layers at sufficiently high pressure are the main pressure-induced structural alterations for graphite-like phases, both ordered and turbostratic. In order to clarify the particular features of the structural mechanism in the case of turbostratic structures, t-BCx has been studied using structural modeling of X-ray powder diffraction patterns obtained in various diffraction geometries as compared to compression axis[8] as well as by Raman spectroscopy up to pressures high enough to cause the formation of the disordered layered high-pressure phase[9]. Using the results obtained, the mechanism of the HP–HT transformation of graphite-like turbostratic phases into metastable diamond-like ones has been proposed[4].
[1] T. Shirasaki, et al., Carbon 2000, 38, 1461. [2] V. L. Solozhenko et al., Appl. Phys. Lett. 2004, 85, 1508. [3] V. L. Solozhenko et al., J. Superhard Mater. 2006, 28, 1. [4] V. L. Solozhenko et al., Phys. Rev. Lett. 2009, 102, 015506. [5] B. E. Warren, Phys. Rev. 1941, 5, 693. [6] V. F. Britun & A. V. Kurdyumov, High Press. Res. 2000, 17, 101. [7] R. E. Franklin, Acta Crystallogr. 1951, 4, 253. [8] V. L. Solozhenko & O. O. Kurakevych, Acta Crystallogr. B 2005, 61, 498. [9] V. L. Solozhenko et al., J. Appl. Phys. 2007, 102, 063509.
*E-mail: [email protected] Keywords: turbostratic structure, high pressure, equation of state, Raman scattering
336
Implementation of ultrasound velocity measurements at high pressure to study micellar dynamics
B. Guignon1*, C. Aparicio1, P.D. Sanz1, V. García-Baonza2, E. Hidalgo2
MALTA Consolider TEAM – 1Departamento de Ingeniería, Instituto del Frío, CSIC, 28040-Madrid, Spain,
2Departamento de Química Física I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040-Madrid, Spain
Micelles are formed by the association of surfactant molecules. These are chemicals of great importance for the industry
[1]. Pressure, like temperature, is able to modify the stability range
and kinetics of micelle formation, and it is also a promising technological variable for food, pharmaceutical and physico-chemical processes. However, little is known about the effect of pressure on micelles behaviour in combination with variables like temperature, ionic strength or other factors. The objective of this work is to evaluate an ultrasonic technique for studying micellar dynamics under high pressure. Firstly, the ultrasonic device is tested and calibrated measuring ultrasound velocity in water under pressure. Secondly, the critical micelar concentration (CMC) of sodium dodecanoate solutions is investigated at 25°C as a function of pressure up to 600 MPa. For this purpose, it is necessary to transpose to high pressure technology, the methodology used at atmospheric pressure to determine the CMC. The technique is validated by comparing the CMC data obtained with existing data from the literature both at atmospheric and high pressures
[2]. Finally, the CMC of sodium dodecanoate
solutions under pressure is determined at 50°C as an original data set. This will allow us to address, in a preliminary way, the effect of pressure in combination with temperature on the CMC of sodium dodecanoate solutions.
[1] J. Texter, T. A. Hatton, Current Opinion in Colloid & Interface Science, 2003, 7, 253. [2] T. S. Brun, H. HØiland, E. Vikingstad, Journal of Colloid and Interface Science, 1978, 63(1),
89.
*Email : [email protected] Keywords: Micelles; Sodium laurate; Critical Micellar Concentration;
337
Influence of nitrobenzene concentration on the detonation waves structure for FEFO/ nitrobenzene solution
V.M. Mochalova*, S.I. Torunov, A.V. Utkin, V.A. Garanin
Institute of Problems of Chemical Physics RAS, Chernogolovka, Russia
The detonation waves structure in liquid HE can change due to inert solvent addition. The dependence of detonation parameters for (bis-(2-fluoro-2,2-dinitroethyl) formal) /nitrobenzene solution (FEFO/NB) from NB concentration was defined. Velocity profiles of the boundary between HE and water window were recorded by laser interferometer VISAR. At investigation of FEFO it was found that particle velocity profile was strongly oscillating with the oscillation amplitude 50 m/s. It means that detonation front is unstable and irregularity size is about 10 µm. The average particle velocity profile corresponds to ZND model. But the transition from reaction zone to unloading wave is so smooth, that it is difficult to define the Chapman-Jouguet (C-J) point. For C-J point definition experiment with the use of two different diameter tubes was conducted. The reaction zone in both cases coincides, but unloading differs. It allowed us to find the C-J point. Reaction time is 400±50 ns, pressure and particle velocity are 23.9±0.5 GPa and 1.98±0.05 km/s respectively.
For FEFO/NB solution it was found that at low NB concentrations (10-20%) oscillations disappeared, that is front was stable. This result was so unusual, because as it should be expected the inert solvent had to increase the instability of detonation front. It was interesting that velocity gradient in the reaction zone in this solution (10-20% NB) was greater than in pure FEFO. At NB concentration increase up to 30 % high-frequency oscillations appeared again. Measurements of reaction zone structure up to critical concentration were conducted, it was about 45%. At average particle velocity profiles Von Neumann spike was distinctly registered.
Thus, dependence of FEFO/NB solution detonation parameters from NB concentration was defined. It was shown that in a pure FEFO and in its solutions with NB concentration exceeding 30% detonation front was unstable.
*E-mail: [email protected] Keywords: detonation wave, FEFO, nitrobenzene.
338
High-pressure synthesis of FeO–ZnO solid solutions with rock salt structure
P.S. Sokolov1,2, A.N. Baranov3, C. Lathe4, V.Z. Turkevich5, V.L. Solozhenko1* 1LPMTM-CNRS, Université Paris Nord, Villetaneuse, France
2Materials Science Department, Moscow State University, Moscow, Russia 3Chemistry Department, Moscow State University, Moscow, Russia
4HASYLAB-DESY, Hamburg, Germany 5 Institute for Superhard Materials of the National Academy of Science, Kiev, Ukraine
Zinc oxide is a IIb-VI wide-band-gape semiconductor. At ambient conditions it has hexagonal wurtzite structure (P63mc) that at high pressures transforms into rock salt structure (Fm3m), however, this phase cannot be quenched down to ambient pressure. Recently, a number of metastable Me
IIO–ZnO solid solutions (Me
II – Ni
2+, Fe
2+, Co
2+, Mn
2+) with rock salt structure
have been synthesized from binary oxides by quenching from 7.7 GPa and 1450-1650 K [1]. It has been found that single-phase rock salt Fe1-xZnxO solid solutions stable at ambient conditions can be synthesized in the 0 < x ≤ 0.5 concentration range. In the present work in situ X-ray diffraction with synchrotron radiation has been used for the first time to study chemical interaction and phase formation in the FeO–ZnO system at 5 GPa and temperatures up to 1300 K.
Experiments have been performed using MAX80 multianvil high-pressure apparatus and energy-dispersive X-ray diffraction at beamline F2.1, DORIS III, HASYLAB-DESY. Experimental details are described elsewhere [2].
At 5 GPa, heating of the FeO–ZnO mixtures (30, 50, 70 and 85 mol.% ZnO) results in chemical interaction and formation of two FeO–ZnO solid solutions with wurtzite and rock salt structures that coexist in a rather wide (~300 K) temperature range. Further heating is accompanied by complete disappearance of the lines of wurtzite solid solution and formation of a single-phase rock salt Fe1-xZnxO solid solution that can be quenched down to ambient pressure. These features are observed for all studied samples irrespective of the stoichiometry, though for reaction mixtures of lower FeO content they are shifted to higher temperatures.
The temperature dependencies of lattice parameters of as-synthesized rock salt Fe1-xZnxO solid solutions have been measured at 5 GPa up to 1300 K, and the corresponding values of linear thermal expansion coefficients have been determined.
The equilibrium phase T–x diagram of the FeO–ZnO system at 5 GPa has been proposed based on the experimental data.
1. A.N. Baranov, P.S. Sokolov, O.O. Kurakevych, V.A. Tafeenko, D. Trots, V.L. Solozhenko, High Press. Res., 2008, 28, 515-519.
2. V.L. Solozhenko, A.N. Baranov, V.Z. Turkevich, Solid State Comm., 2006, 138, 534-537.
*E-mail: [email protected] Keywords: zinc oxide, iron (II) oxide, solid solution, high pressure
339
Layered cobaltates NaxCoO2 under pressure
C. Popescu1*, J.P. Itié2, A. Congeduti2, L. Pinsard-Gaudart1, N. Dragoe1 1LEMHE, ICMMO, UMR 8182, University of South-Paris, 91405 Orsay, France
2Soleil Synchrotron , UR1, 91192 Gif-sur-Yvette, France.
Layered cobaltates NaxCoO2 have attracted increased attention due to their interesting magnetic and thermoelectric properties, as well as for remarkable analogies to colossal magnetoresistive manganite materials, and high superconducting transition temperature cuprate oxides. In particular: - superconductivity is induced in hydrated Na0.35CoO2, - a high thermoelectric power metallic conductor is found for Na0.7CoO2 and –Na0.5CoO2 appears to be insulating at low temperatures due to the ordering of Co ion charges [1]. The structure of Na0.7CoO2 consists of alternating layers of Na and CoO2 planes, stacked along the c axis in a hexagonal structure, with Na atoms occupying two crystallographic sites, not necessarily in an ordered pattern.
Pressure is an ideal tool for investing the structural properties of these systems because it allows avoiding chemical substitution as well as separating the electronic and structural degrees of freedom. Increasing pressure is providing access to structural changes in a similar way to varying doping but the role of the disorder of the Na ions will be removed. In a previous work structural changes were observed for the compound Na0.74CoO2 by in situ Raman scattering and energy-dispersive X-ray diffraction methods at pressures up to 41 GPa. The discontinuity of the lattice parameters and Raman observations revealed a phase transition between 10-12 GPa [2].
X-ray Absorption Spectra of cobaltates NaxCoO2 (with x=0.75 and 0.79) were collected at Lucia Beamline (SLS Synchrotron) under variable pressure (0-20 GPa) at room temperature. The analysis of the Exafs spectra permits the study at local level of the structural distortion of the bond length Co-O and Co-Co which showed no phase transition up to 20 GPa. These data will be discussed here.
[1] Q. Huang, M. L. Foo, R. A. Pascal, J. W. Lyn, B. H. Toby, H. W. Zanderbergen, R.V. Cava, Physical Review B. 2004, 70, 184110.
[2] F. X. Zhang, S. K. Saxena, C. S. Zha, Journal of Solid State Chemistry. 2007, 180, 1759.
* E-mail Keywords: cobaltates, pressure, Exafs.
340
Molecular dynamics calculations of activation volumes
E. Deglint, E Edwards, N. Boon, N. Weinberg*
Department of Chemistry, University of the Fraser Valley, Abbotsford, Canada
Our approach toward calculating reaction and activation volumes is based on molecular dynamics simulations and depends on availability of reliable force field parameters. The parameters are unavailable in the literature for unstable species, such as transition states. We propose a new parameterization scheme suitable for these species, and apply it to calculate activation volumes of the dimerization of cyclopentadiene, a well-studied Diels-Alder reaction demonstrating significant sensitivity to the external pressure. The results of calculations agree well with the experimental data.
*Email : [email protected] Keywords: activation volumes, high pressure reactions, molecular dynamics
341
In situ EXAFS studies of Ta—N systems at high pressure
K. Woodhead1, P.F. McMillan1, A. Hector2, G. Aquilanti3 and S. Pascarelli4 1Department of Chemistry, University College London, London, UK,
2Department of Chemistry, University of Southampton, Southampton, UK 3Elettra, Trieste, Ital
4ESRF,Grenoble, France
New microbeam XAS facilities at ID24 offer the possibility of studies with a high degree of spatial resolution[1]. This has been employed here to investigate the oxidation state and local structure of tantalum nitrides and oxynitrides in the DAC at high pressures. The Ta—N system exhibits a rich phase diagram extending from TaN to Ta3N5, the latter of which is expected to undergo phase transitions at high pressures[2]. Many binary nitrides possess useful mechanical, optical or electronic properties, and these new phases are predicted to exhibit very high bulk moduli. Our new materials are prepared from amorphous precursors with a TaxNy composition[3], and we are exploring their synthesis in the laser-heated DAC, and the subsequent coexistence of new phases.
[1] S Pascarelli, O Mathon, G Aquilanti, J. Synchrotron Rad., 2006, 13, 351 [2] P Kroll, T Schröter and M Peters, Angew. Chem. Int. Ed., 2005, 44, 4249 [3] AW Jackson, O Shebanova, AL Hector, PF McMillan, J. Solid State Chem., 2006, 179,1383
*Email : [email protected] Keywords : Tantalum nitride; EXAFS; high pressure, Chemistry
342
High pressure inelastic x-ray studies of nitrogen-containing compounds: melamine and gallium nitride.
M. Pravica*1, S. Tkachev1 and P. Chow2 1High Pressure Science and Engineering Center (HiPSEC) and Department of Physics and
Astronomy, University of Nevada, Las Vegas, Las Vegas, Nevada 89154-4002 USA, 2High Pressure Collaborative Access Team, Advanced Photon Source, Argonne, IL 60439 and
Carnegie Geophysical Laboratory, Washington, DC 2005
GaN has been suggested as a high pressure sensor [1] and melamine has been investigated in the past as a possible precursor to make superhard C-N containing materials with pressure [2]. Thus, high pressure studies examining possible bonding and/or deep level electronic changes with pressure would be of great use. We present two separate high pressure studies of nitrogen-containing compounds using inelastic x-ray spectroscopic methods at the High Pressure Collaborative Access team’s 16 ID-D beamline at the Advanced Photon Source. In the first study, the wide band gap material gallium nitride (GaN), we examined the pressure dependence of the Kα1 and Kα2 lines up to ~15 GPa using a Paderborn-style diamond anvil cell (DAC) with Be confining gaskets. In the second experiment, we used x-ray Raman spectroscopy to interrogate a sample of melamine up to ~15 GPa with a similar diamond cell and Be confining gaskets.
[1] K-A. Son et al., 2005 IEEE Sens., 1259. [2] D. L. Yu, J. L. He, Z. Y. Liu, B. Xu, D. C. Li and Y. J. Tian, J. Mater. Sci. 2007, 43, 689.
*E-mail : [email protected] Keywords : XRS, XES, nitrogen bonds
343
Structural transition of the layered AuCrS2 system under high pressure
S. J.E. Carlsson1, I. Yamada2, Y. Le Godec1, A. Gauzzi1, M. Mezouar3
1IMPMC, Université Pierre et Marie Curie, Paris, France 2Graduate School of Science and Engineering, Ehime University, Matsuyama, Japan
3European Synchrotron Radiation Facility, Grenoble, France
Delafossite-typy oxides AMO2 (A=Cu, Ag, Pd; M=Sc, Ga, Al, Co) display a variety of unusual physical properties with perhaps the most notable being a negative thermal expansion of the c-axis[1]. Its origin is not fully understood but it is thought to be strongly related to the instability of the linear O-A-O bonds linking the MO2 layers. Pressure studies would be expected to elucidate this point but there are very few reports of the high pressure behavior of delafossite-type compounds. Evidence of a pressure-induced structural phase transition has been reported for CuGaO2 but with no clear picture of the high pressure phase[2]. In this work we have focused on the sulphur counterpart, AMS2, of these compounds. With the larger compressibility of sulphur, as compared with oxygen, and the more covalent character of the S-A-S bond, larger pressure-induced affects would be expected.
The structural stability and the PT diagram of the ternary sulphide AuCrS2[3] below 15 GPa and 1500 K has been explored in situ using synchrotron X-ray diffraction in combination with the Paris-Edinburgh cell. It was found that a reversible pressure-induced structural phase transition takes place between 5.0 and 6.5 GPa at ambient temperature. Below the transition point, the c-axis remains unchanged, while the a-axis shrinks. Above the transition, a discontinuity of the unit-cell volume is observed together with an unusual expansion of the caxis. Rietveld refinements of the high pressure data confirm a transition from a
centrosymmetric to a non-centrosymmetric phase (R3 m → R3m) with the Au environment strongly affected indicating a charge imbalance of the two sulphur layers. Neither the volume discontinuity nor the c-axis expansion was reported in CuGaO2. Furthermore, the reversibility of the phase transition of AuCrS2 was not observed in CuGaO2, indicating that the transition is of a new kind for a delafossite-type compound.
[1] J. Li, A.W. Sleight, C.Y. Jones, H.B. Toby, J. of Solid State Chem. 2005, 178, 285. [2] J. Pellicer-Porres, A. Segura, C. Ferrer-Roca, D. Martinez-Garcia, J. A. Sans, E. Martinez J.P.
Itié, A.Polian, F. Baudelet, A. Muños, P. Rodriguez-Hernandes, P. Munsch, Phys. Rev. B. 2004, 69, 024109.
[3] H. Fukuoka, S. Sakashita, S. Yamanaka, J. of Solid State Chem. 1999, 148, 487.
*Email : [email protected] Keywords : Synchrotron-radiation, High Pressure, Crystal-structure
344
Pressure-induced polymorphism in 1,4-diazabicyclo[2.2.2]octane complexes
A. Olejniczak and A. Katrusiak*
Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland
1,4-Diazabicyclo[2.2.2]octane hydroiodide (dabcoHI, [C6H13N2]+I-) is the first organic and
stoichiometric compound for which anisotropic relaxor dielectric properties have been evidenced
[1]. A multitude of new polymorphs of dabcoHI has been obtained at elevated
pressure and temperature. The crystal symmetries identified for the nonslovated dabcoHI
crystals so far are: P6 m2, Pbcm, Pmc21, Pmm2, Cmm2, P2/c. In all the structures determined by X-ray diffraction linear or nearly linear chains of cations are linked by NH
+···N hydrogen
bonds. In two phases, space groups Pbcm and Pmc21, the protons are ordered in the NH+···N
bonds, while in all other phases the proton is 50:50 disordered in two sites at the nitrogen atoms. The main structural differences between the polymorphs are in the arrangement of the poly-cationic chains and iodide anions, and in the conformation of dabco cations. The polymorph obtained at 0.20(5) GPa was recovered at normal conditions after releasing
pressure and for weeks did not transform to phase I (space group, P6 m2), however pulverized phase II (space group, Pbcm) at ambient pressure transforms slowly into phase I. When crystallized from methanol, up to 1.70(5) GPa dabcoHI forms unsolvated crystals, and at higher pressure solvates could be obtained only.
*1+ M. Szafraoski, A. Katrusiak, J. Phys. Chem. B. 2008, 112, 6779. 2008, 15, 32.
*Email: [email protected] http://hpc.amu.edu.pl Keywords: polymorphism, ferroelectric relaxor, hydrogen bonding, proton disordering
345
Synthesis
Lectures High-pressure synthesis of novel superhard phases in the B-C-N system ____________ 347
Collapsed Silicalite at High Pressure: a Novel Form of Topologically Ordered
Amorphous Silica _________________________________________________ 348
From mixing to reactivity: Novel Ge0.9Sn0.1 solid solution formation at 10 GPa
after heating _____________________________________________________ 349
Synthesis, structural and magnetic disordering in the IrSr2RECu2O8+x family of
metalo-cuprates by HP+HT oxidation _________________________________ 350
Posters SY 01 : Shock compressibility of silicon nitride porous samples ____________________ 351
SY 02 : In situ kinetic studies at HPHT using generalized Avrami relationships. ______ 352
SY 03 : Baric dependences of the thermoelectric and electric properties of
amorphous copper chalcogenides ____________________________________ 353
SY 04 : Synthesis and electrical properties of high pressure phases AXCu3V4O12 (A
- Er, Tm) _________________________________________________________ 354
SY 05 : Effect of high pressure on electrical properties of some amorphous
chalcogenides from the system Ag-Ge-As-S ____________________________ 355
SY 06 : High pressure-high temperature synthesis and characterisation of bulk
superhard nanocomposites in the systems B-N and Ti-(Al-Si)-N ____________ 356
SY 07 : An in situ X-ray absorption spectroscopy study of the solubility of
cristobalite-type Si0.8Ge0.2O2 and aqueous speciation of Ge in
hydrothermal conditions ___________________________________________ 357
SY 08 : Single crystal growth of BiMnO3 under high pressure - high temperature _____ 358
SY 09 : High pressure synthesis of functionalized boron nitride by doping___________ 359
SY 10 : High pressure synthesis of the perovskite series RCu3Mn4O12:
enhancement of the Curie temperature driven by chemical pressure of
R3+
cations (R=La, rare earth) ________________________________________ 360
SY 11 : Influence of the nanodiamonds adittion on PDC Properties ________________ 361
SY 12 : The morphology and diamond properties synthesized in the Mg-Ni–C
system __________________________________________________________ 362
SY 13 : Study of diamonds production for analysis register synthesis parameters ____ 363
SY 14 : Hydrothermal/solvothermal synhtesis of new hybrid materials with
potential applications in nanomedicine _______________________________ 364
SY 15 : Extrusion-activated thermal explosion applied to intermetallics
processing _______________________________________________________ 365
SY 16 : High Pressure Chemistry of C-N-H Systems: Results from the Laser-
Heated Diamond Anvil Cell _________________________________________ 366
346
347
High-pressure synthesis of novel superhard phases in the B-C-N system
V. L. Solozhenko
LPMTM-CNRS, Université Paris Nord, 93430 Villetaneuse, France
The growing demand for advanced superhard materials simulated the search for novel high pressure phases that are more thermally and chemically stable than diamond and harder than cubic boron nitride (cBN). Following the synthesis of diamond-like BC2N [1] and BCN [2], very recently a number of new superhard phases of the B-C-N system has been synthesized.
γ-B28 New high-pressure form of elemental boron, orthorhombic γ-B28 theoretically predicted by Oganov et al. [3] has been synthesized in the 12-20 GPa pressure range at temperatures above 1800 K. Compressibility of γ-B28 has been measured to 65 GPa; and a fit of the experimental p-V data to the Vinet equation of state yields bulk modulus of 237(5) GPa with its first pressure derivative of 2.7(3) [4]. Vickers hardness of polycrystalline bulk γ-B28 was found to be 50(11) GPa [5] which is higher than the hardness of other boron polymorphs.
d-BC5 A new superhard phase, diamond-like BC5, has been synthesized by solid-state transformation of graphite-like BC5 at pressures above 20 GPa and temperatures of about 2200 K in a laser-heated diamond anvil cell and a multianvil press [6]. Lattice parameter of d-BC5 at ambient conditions is a = 3.635(8) Å which is larger than that diamond. The phase is metastable and at high temperatures demonstrates a clear tendency to segregate into carbon and boron carbides, however, at ambient pressure d-BC5 has been found to be much more thermally stable (up to 1900 K) than nanocrystalline diamond with the same grain size. Bulk modulus of d-BC5 was found to be 335(8) GPa and is exceeded only by the bulk moduli of diamond and cBN. Well-sintered millimeter-sized bulks synthesized in a multianvil press are conductive and exhibit extreme hardness (HV = 71(8) GPa) approaching that of diamond.
B13N2 New rhombohedral boron subnitride B13N2 has been synthesized by crystallization from
the B–BN melt at 5 GPa [7,8]. The structure of B13N2 belongs to the R3 m space group and represents a new structural type [8]. The subnitride is an individual compound and not a solid solution, in contrast to boron carbide. According to the predictions made in the framework of thermodynamic model of hardness [9], B13N2 is expected to exhibit hardness of about 40 GPa comparable to that of commercial polycrystalline cubic boron nitride.
[1] V.L. Solozhenko et al., Appl. Phys. Lett., 2001, 78, 1385. [2] V.L. Solozhenko, High Press. Res., 2002, 22, 519. [3] A.R. Oganov et al., Nature, 2009, 457, 863. [4] Y. Le Godec et al., Solid State Comm., doi:10.1016/j.ssc.2009.05.025 [5] V.L. Solozhenko et al., J. Superhard Mater., 2008, 30, 428 [6] V.L. Solozhenko et al., Phys. Rev. Lett., 2009, 102, 015506. [7] V.L. Solozhenko, O.O. Kurakevych, J. Phys. : Conf. Ser., 2008, 121, 062001. [8] V.L. Solozhenko, O.O. Kurakevych, J. Solid State Chem., 2009, 182, 1359. [9] V.A. Mukhanov et al., High Press. Res., 2008, 28, 531.
Email : [email protected] Keywords: high-pressure synthesis, superhard phases, B-C-N system
348
Collapsed silicalite at high pressure: a novel form of topologically ordered amorphous silica
J. Haines1, C. Levelut2, A. Isambert3, P. Hébert3, S. Kohara4, D. A. Keen5, T. Hammouda6, D. Andrault6
1Institut Charles Gerhardt Montpellier, PMOF, UMR 5253 CNRS, Université Montpellier II, Montpellier, France
2Laboratoire des Colloides, Verres et Nanomatériaux, UMR 5587 CNRS, Université Montpellier II, Montpellier, France
3CEA, DAM Le Ripault, Monts, France 4Research & Utilization Division, Japan Synchrotron Radiation Research Institute (Spring 8),
Hyogo, Japan 5ISIS Facility, Rutherford Appleton Laboratory, HSIC, Didcot, Oxfordshire, United Kingdom &
Department of Physics, Oxford University, Clarendon Laboratory, Oxford, United Kingdom 6Laboratoire Magmas et Volcans, UMR CNRS 6524, Université Blaise Pascal, Clermont-
Ferrand, France.
The highly-compressible SiO2 zeolite, silicalite, was found to transform to a dense amorphous form at high pressure by in situ, x-ray powder diffraction. In order to directly study the structure of the amorphous form, a millimeter-sized sample was prepared and recovered from 20 GPa at room temperature using a multi-anvil, high-pressure device. The recovered material was transparent and glass-like in appearance. The structure of the recovered, amorphous form was determined by Reverse Monte Carlo modeling of total x-ray scattering data obtained at Spring-8. This new dense amorphous form of silica is distinct from vitreous SiO2 and retains the basic topology of the starting crystalline phase, while being amorphous over the different length scales probed by Raman and x-ray scattering due to strong geometrical distortions. This topologically-ordered amorphous material thus exhibits a low entropy, will be characterized by superior mechanical properties and may tend to approach the state of a“perfect glass” (i.e. structural order close to that of the crystal). The large volume collapse during the formation of this material may be of considerable interest for new applications[1] in shock wave absorption.
Fig. 1. Photograph and RMC model of pressure amorphized silicalite
[1] A. Isambert, E. Angot, P. Hébert, J. Haines, C. Levelut, R. Le Parc, Y. Ohishi, S. Kohara, D. A. Keen, J. Mater. Chem. 2008, 18, 5746.
* E-mail : [email protected] Keywords: Pressure-induced amorphization, Multi-anvil device, Glassy and amorphous materials, Total x-ray scattering
349
From mixing to reactivity: novel Ge0.9Sn0.1 solid solution formation at 10 GPa after heating
G. Serghiou*1, C. Guillaume1,7, A. Thomson1,8, N. Russell1, A. J. McGaff1,9, J. P. Morniroli2, D.J. Frost3, N. Odling4, C. E. Jeffree5, M. Mezouar6
1 University of Edinburgh, School of Engineering, EH9 3JL, Edinburgh UK 2 Laboratoire de Métallurgie Physique et Génie des Matériaux, CNRS 8517,
Université des Sciences et Technologies de Lille 59655 Villeneuve d’Ascq Cedex France 3 Bayerisches Geoinstitut, Universität Bayreuth,95440, Bayreuth, Germany 4 University of Edinburgh, School of Geosciences, EH9 3JW, Edinburgh, UK
5 University of Edinburgh, School of Biological Sciences, EH9 3JR, Edinburgh, UK 6 European Synchrotron Research Facility, Boîte Postale 220, 38043 Grenoble, France
A significant barrier to promising new materials is that desired elements do not react with each other. In group IV solids, despite their importance for many applications no bulk GeSn crystal existed previously. This status quo was changed by transforming Ge and Sn at 10 GPa to states where their crystal symmetries, atomic radii, nominal valencies and electronegativities are similar. After melting Ge-Sn mixtures at 10 GPa followed by annealing, a tetragonal Ge0.9Sn0.1 solid solution was recovered (space group P43212, a = 6.014 (1) Å , c = 7.057 (1) Å, Z = 12). Our analysis of numerous further high pressure experiments from up to 2000 K revealed segregation of Sn from Ge at and below 9 GPa, due to dissimilar electronic and crystal structures, and various degrees of Ge and Sn mixtures above 12 GPa due to similar electronic, and different crystal structures. One additional factor that may promote Sn uptake by Ge near 10 GPa, is that the two undergo crystal and electronic phase transitions there, and Ge is near a low-lying triple point, and notably, this region also figures prominently in Ge-metallic glass formation. Further, calculations on tetragonal Ge, find it to have a direct band-gap. Hence, our tetragonal Ge-rich solid solution is of optoelectronic interest because it most likely exhibits, unlike the other ambient-pressure-prepared group IV elements and binaries, a direct band-gap, which can be tuned with Sn-content. A synthesis here of a Si based tetragonal GeSi phase is also significant partly because of a prediction that a tetragonal Si phase, if made, could, exhibit a higher Tc than other Si-polytypes. Analytical methods employed include transmission electron microscopy, scanning electron microscopy and X-ray diffraction. Further, temperature profiles, together with temperature and pressure treatments are exploited in evaluating chemical, morphological and structural evolution.
*Email : [email protected]
Present addresses: 7School School of Physics, University of Edinburgh, Mayfield Road, EH9 3JZ, Edinburgh UK, 8BP Chemicals Ltd, HU12 DS, Hull, UK, 9Diageo Scotland, EH12 9DT, Edinburgh,UK
Novel synthesis, reactivity, mixing, direct band-gap
350
Synthesis, structural and magnetic disordering in the IrSr2RECu2O8+x family of metalo-cuprates by HP+HT oxidation
A. J. Dos Santos-García1,2, A. M. Arévalo-López1, J. Fernández- San Julian1, M. Á. Alario-Franco1*
1 Universidad Complutense de Madrid, Madrid, Spain 2 Parque Científico y Tecnológico de Albacete & Universidad de Castilla-La Mancha,
Albacete, Spain.
We have been working for sometime in the family of compounds MSr2RECu2O8, loosely called ‘metalo-cuprates’, where M is a transition metal and RE is a Rare Earth element and yttrium. More than 20 materials have been successfully prepared and characterised, most of them synthesised at high pressure (HP) and high temperature (HT) conditions
[1, 2]. Among them, the
irido-cuprates, are particularly interesting since their magnetic/electric properties show a remarkable dependence with the rare earth anisotropy. Ferrimagnetism, re-entrant spin-glass-like behaviour and antiferromagnetism with a magnetic field induced spin reorientation are found in these iridates
[3-5].
Furthermore, searching for the optimal synthesis conditions for these iridates, we have been able to isolate a new cubic perovskite in which both the A and B positions are disordered even if occupied by rather different cations: (Sr2RE)(Cu2Ir)O9-δ. Although the average structure seems to change with cation size, the true structure is common for all of these materials and
has orthorhombic symmetry (S. G. Pbnm, cell ~√2ap×√2ap×2ap). Not unexpectedly, the disordered phases are paramagnetic.
A final point worthy of note is that, even under high pressure, at sufficiently high temperatures one gets an increase in the symmetry and a cubic disordered phase in an oxidation reaction.
Acknowledgements: We thank Prof R. Sáez Pouche and Dr. J van Dujin for their contribution to the early work and valuable discussions
[1] M.Á. Alario-Franco, R. Ruiz-Bustos, and A.J. Dos Santos-García, Inorg. Chem. 2008, 47, 6475.
[2] R. Ruiz-Bustos, M.H. Aguirre, and M.Á. Alario-Franco, Inorg. Chem. 2005, 44, 3063. [3] A.J. Dos Santos-García, M.H. Aguirre, E. Morán, R. Saéz-Puche, and M.Á. Alario-Franco, J.
Solid State Chem. 2006, 179, 1275. [4] A.J. Dos Santos-García, J. Van Duijn, R. Sáez-Puche, G. Heymann, H. Hupertz, and M.A.
Alario-Franco, J. Solid State Chem. 2008, 181, 1167. [5] A.J. Dos Santos-García, J.Van Duijn, and M.Á.Alario-Franco, J. Solid State Chem. 2008, 181,
3317.
*Email: [email protected]
351
Shock compressibility of silicon nitride porous samples
V.V. Yakushev*, A.V. Utkin, A.N. Zhukov
IPCP RAS, Moscow region, Chernogolovka, Russia.
It was investigated in the present work the behavior of hexagonal β - modification silicon nitride porous samples with porosity of ~ 15% at high pressure shock loading up to 55 GPa.
Silicon nitride is intensively investigated because of its outstanding mechanical, electrical and termal characteristics. Three silicon nitride crystal modifications are known: α - and β – with the hexagonal structure and recently synthesized c – modification with cubic structure
[1].
Unlike c – modification, α - and β – modifications are well studied. The interest to the high density c – modification mainly caused by its hardness, close to hardness of cubic boron nitride and diamond and it’s high chemical stability.
It is known that c-Si3N4 synthesis is connected with considerable difficulties caused by both high phase transition parameters and trifling c-phase yield on available today methods of synthesis. C-phase manufacture in static, shock and detonation waves from β-phase. Detonation method expect to be the most acceptable for c-phase synthesis. Now it is of great importance to define the optimal conditions of the synthesis on pressure and temperature. This can be made by β – с – balance curve construction with help of equation of state. Having Hugoniots for samples of various porosities enables to construct equation of state with good accuracy. It was measured the Hugoniot for porous (15%) samples β-Si3N4 in this work. It was the least porosity value that permits to manufacture high quality samples.
Samples have been made by pressing of silicon nitride fine-dyspersated powder, manufactured by self-propagating high-temperature synthesis, in the high pressure chamber at 2 GPa and 1600
oC. Samples loading carried out by high speed Al impactors, accelerated
with explode products, through Al and Cu shields. Sample surface velocity registration was made by laser Doppler velocimeter VISAR.
Hugoniot for porous samples was constructed by measuring of two parameters in experiment: shock wave velocity and particle velocity at the boundary of the sample with water window. It was found that Hugoniot has no peculiarities connected with the phase transition. Comparing of Hugoniot with that for solid samples taken from
[2] (in coordinates
pressure - specific volume) shown that porous adiabat cross solid adiabat at 25 GPa and over this point lies below it in spite of more powerful heating of porous material. That can be explained by the strong temperature influence on the pressure. The increase of the temperature brings to the phase transition pressure decrease. Such temperature influence was observed in
[3]. Consequently the curve of the transition beginning has negative slope in
P-T. This points out the direction for searching of optimal synthesis parameters. Namely, the phase transition promotes by increasing both pressure and temperature.
Yunoshev A.S., Combustion, Explosion, and Shock Waves, 2004, V. 40, N 3, P370-373. Hongliang He, T. Sekine, T. Kobayashi, H. Hirosaki, Isao Suzuki., Phys. Rev. B., 2000, Vol 62, N
17, P. 11412-11417. Sekine T., He Hongliang, Kobayashi T., Zhang Ming, and Xu Fangfanf., Appl. Phys. Letters.
2000, V. 76, N 25, P. 3706-3708. *Email: [email protected]
352
In situ kinetic studies at HPHT using generalized Avrami relationships.
O O. Kurakevych*
Institute for Superhard Materials, NAS of Ukraine, 04074 Kiev, Ukraine
The restricted growth of a solid phase from a fluid has been studied in the framework of the Johnson-Mehl-Avrami model[1]. In the case of 3-D growth, the 3- and 2-D space restrictions due to the particle“intergrowth” have been studied. The resulting equations relate the true and extended
conversion degrees ( & ex), and allow us to describe the overlap in systems with various behaviors of the mean distance between growing particles and various nucleation types.
The main feature of the proposed generalization of the Johnson-Mehl-Avrami model consists in the introduction of the ‘growth space’ (GS) that implies the space where growing crystals (i.e. centers of growing crystals, origins of growth or germs) are located.
1. In the case that the GS volume remains constant during the process (the growing crystals have fixed positions in space and/or the mean interparticle distance does not change), the relationship between
true and extended conversion degrees becomes ex = − (1/ ) ln(1− ) (1), where is a ratio between the final volume of new phase and volume of GS. This equation may be useful in the case of heterogeneous nucleation when the particles are randomly distributed in the whole system or when we do not know exactly the conversion degree at the end of the transformation. The letter case is often responsible for the deviation from Avrami’s kinetics in solid-phase transformations.
2. If the process is accompanied by a change in the growth space volume (the mean interlayer distance is not constant during the process), the relationship between true and extended conversion degrees is
ex = + 0.5 2 (2), where is a ratio the final volume of new phase and volume of solution. The
equation suggests that the volume of liquid remains constant and the volume of GS increases due to the increase of the volume of forming phase. The described situation takes place during the crystallization from the oversaturated fluid solution.
Analysis of derived above eq. (1) shows that for from the [0; 0.25] interval, ex is close to even when the conversion degree is over 40%. So, the growth may be considered as free event at high
transformation degrees. The ex versus -curve tends to Avrami’s curve only if is very close to 1. At
the same time, for eq. (2) Avrami’s curve is not the bound any more. Only, if 1 and conversion degree doesn’t exceed 40%, the curve may be satisfactorily interpolated by Avrami’s one.
3. The case that the dimensionality of the growth space is lower then that of the particle growth is the most complicated for consideration. The relatively simple equations may be formulated only based on certain assumptions, which, however, are commonly met in practice. The relationship between true and
extended conversion degrees is =1/3
(1-e-(Bex2/3)
)/B (3) under assumption of the instantaneous nucleation on a plane and growth of prismatic crystals. The nature of the B constant and applicability of eq. (3) have been discussed elsewhere[1].
The formulated equations have been applied to the in situ data on the crystallization of cBN and MgB2 under HPHT for the analysis of experimental kinetic curves. It has been also illustrated that different models can well fit the experimental kinetic data, and only detailed analysis of obtained parameters and additional microstructural studies may give the correct solution to the inverse kinetic problem.
[1] O. O. Kurakevych, Mater. Chem. Phys. 2007, 105, 401.
*E-mail: [email protected] Keywords: kinetics, phase transformation
353
Baric dependences of the thermoelectric and electric properties of amorphous copper chalcogenides
N.V . Melnikova 1 * , A.Y. Mollaev2, L.A. Saipullaeva2, A.G. Alibekov2, O.L. Kheifets1, A.N. Babushkin1
1Low Temperature Physics Dept ,Ural State University, Ekaterinburg, Russia 2Institute of Physics of Dagestan Scientific Centre of RAS, Makhachkala, Russia
The purpose of this work is a study of a possibility of a transition from a high-ohmic to low-ohmic condition and structural changes at pressures up to 50 GPa of amorphouscopper chalcogenides from the system (GeSe)1-x(CuAsSe2)x which possess of thermistor and switch properties. The baric dependences of a thermoemf, an impedance, a permittivity, atangent of loss angle at increase and decrease of pressure in the frequency range 0.1-200 kHz were analyzed.
The hydrostatic pressure up to 0,7 GPa were achieved in the kerosene - oil – pentane mix in the beryllium bronze cell [1]. The hydrostatic pressure up to 8 GPa were achieved in the flat carbide wolfram anvil cell with hole. The sample was located in fluorocarbon polymer capsule, filled by a ethanol- methanol mix [2]. High pressures at 12–50 GPa have been generated in the cell with synthetic carbonadotype diamond anvils of the "rounded
coneplane" type [3]. For creation of temperature gradient one of the anvils was warmed. The baric dependences of a resistivity of the semiconductor sample (GeSe)0.05(CuAsSe2)0.95 in the pressure range 0-7 GPa are shown on Figure 1. At a pressure 12-50 GPa a resistance hysteresis was observed. The thermoemf decreased at a pressure decrease and remained below than was before the increase of pressure. The pressure ranges of noticeable changes of thermoemf and electric properties are identical. This changes can be connected to probable crystallization and structural
[1] A.Yu.Mollaev, L.A.Saipulaeva, R.K.Arslanov and S.F.Marenkin. Inorganic Materials, 2001, 37
(4), 327. [2] L.G.Khvostantsev, L.P.Vereshchagin, A.P.Novikov. Device of Toroid type for high pressure
generation. High Temp.-High Pressure, 1977 , 9(6), 637. [3] L.F.Vereshchagin et al. High Temperatures - High Pressures, 1974 , 6. 499.
*Email : [email protected]
Fig 1. The baric dependences of the transitions. resistivity of (GeSe)0.05(CuAsSe2)0.95 at increase (1) and decrease (2) of pressure.
354
Synthesis and electrical properties of high pressure phases AXCu3V4O12 (A - Er, Tm)
N.I. Kadyrova1, N.V. Melnikova2*, I.S. Ustinova2, Y.G. Zaynulin1, A.N. Babushkin2 1Institute of Solid State Chemistry of Urals Breanch of Russian Academy of Sciences,
Ekaterinburg, Russia 2Low Temperature Physics Dept , Ural State University, Ekaterinburg, Russia
Perovskite-like compounds of the general formula ACu3B4O12, where A – mono-, di-,tri-, or tetracharged cation or a vacancy, element B – Ti, Mn, Ge, Ru, Ti+Ta(Nb, Sb) were intensively studied the last years. It is related to interesting electrical and magnetic properties of mentioned compounds [1,2].
The purpose of research was a synthesis of AxCu3B4O12 (А- Er, Tm, B - V) and a study of the crystal structure, of electrical and magnetic properties in a broad range of frequencies, temperatures and pressures.
The synthesis was carried out at high pressures and high temperatures in the high pressure cell of “toroid” type. Pure Er2O3, Tm2O3, V2O5, Cu2O and ultradispersed electrolytic copper were used as initial components for synthesis of AxCu3B4O12, (А- Er, Tm, B - V). In the conditions of pressure 8 GPa and temperatures 1000°С during 30 min. New perovskitelike compounds Er0.73Cu3V4O12 and Tm0.75Cu3V4O12 have been synthesized. The crystal structure was determined. The oxides Er0.73Cu3V4O12 and Tm0.75Cu3V4O12 crystallize in a cubic symmetry
(sp. gr. Im3 , Z= 2) with the lattice parameters a = 7.266 Å and 7.262 Å respectively.
The electrical properties of synthesized compounds were investigated on a direct current and by a method of impedance spectroscopy in the frequency range from 1 kHz to 200 kHz at temperatures 10-400 K at pressures up to 50 GPa. High pressure from 15 GPa to 50 GPa has been generated in the diamond anvil cell (DAC) with anvils of the "rounded cone-plane" type made of synthetic carbonado-type diamonds.The baric dependences of an impedance, a conductivity and a tangent of loss angle at increase and decrease of pressure were analyzed. It was established the compounds are characterized by a positive values of a magnetic susceptibility.
[1] N. I. Kadyrova, G. S. Zakharova, Y.G.Zainulin, V.L. Volkov, T.V. Dyachkova, A.P. Tyutyunnik and V.G. Zubkov, Dokl. Chem., 2003, 392, 251.
[2] Hiroshi Shiraki, Takashi Saito, Masaki Azuma, Yuichi Shimakawa. J. of the Physical Society of Japan, 2008, 77, No. 6, 064705.
*Email: [email protected]
355
Effect of high pressure on electrical properties of some amorphous chalcogenides from the system Ag-Ge-As-S
O.L. Kheifets*, N.V. Melnikova, A.N. Babushkin, E.F. Shakirov, A.V. Tebenkov
Ural State University, Ekaterinburg, Russia
Multi-component chalcogenides of a silver are known as perspective materials for the scientific and applied purposes [1-2]. The investigation of physical properties of these materials at various external influences allows to reveal changes of the crystal and electronic structure, opens new opportunities for creation of devices on their basis [3]. The purpose of this work is the research of electrical properties of amorphous chalcogenides AgGe1+xAs1-xS3
(x=0.5, 0.6) at the pressure up to 50 GPa in the frequency range 0.1 kHz-200 kHz.
The synthesised compounds have grey colour and metal shine and on the data of X-ray analysis they are quasi-X-rays amorphous. High pressure up to 50 GPa has been generated in the diamond anvil cell (DAC) with anvils of the "rounded coneplane" (Verechagin-Yakovlev) type made of synthetic carbonado-type diamonds [4]. These anvils are good conductors and allow to measure the electrophysical properties of the sample placed in the DAC. Electrical properties were investigated by means of the investigated-analyser of impedance RLC-2000 in the frequency range 1-200 kHz.
The typical hodographs of the impedance of AgGe1+xAs1-xS3 (x=0.5, 0.6) at different pressures at loading of the sample are shown in Fig.1. The hysteresis of a resistance at unloading from a sample have been investigated. The areas of essential change of the electric characteristics were determined from an analysis of the hodographs, of pressure dependencies of resistance and of the tangent of dielectric losses angle and from the frequency conductance dependencies.
A comparison of the properties of synthesised compounds with properties of AgGe1+xAs1-xS3 (x=0.1, 0.9) and AgGeAsS3 at high pressures was carried out.
The researches are executed at partial financial support of RFBR (grant 09-02-01316-a).
*1+ Baranova Е.R. et al., SSI, , 415 (2002) [2] Kheifets O. et al, Low Temp.Ph., , 280 (2007) [3] N.V.Melnikova, et al., ISJAEE, , 56 (2007) [4] L.F.Vereshchagin et al., High Temperatures - High Pressures, . 499 (1974)
*Email [email protected]
Годограф Импеданса 631 - Нагружение
23
25,3
28,1 29,2
30,332,4
>42,3
0,00E+00
2,00E+05
4,00E+05
6,00E+05
8,00E+05
1,00E+06
1,20E+06
1,40E+06
1,60E+06
1,80E+06
2,00E+06
0,00E+00 5,00E+05 1,00E+06 1,50E+06 2,00E+06 2,50E+06 3,00E+06 3,50E+06
Re(Z) [Ом]
Im(Z
) [О
м]
23
25,3
26,9
28,1
29,2
30,3
31,4
32,4
33,5
34,5
35,5
36,3
37,22
37,8
38,5
39,2
39,9
40,6
41,3
41,9
42,3
>42,3
19,2
0
356
High pressure-high temperature synthesis and characterisation of bulk superhard nanocomposites in the systems B-N and Ti-(Al-Si)-N
T. Barsukova1, M.R. Schwarz1, E. Kroke*1, M. Motylenko2, D. Rafaja2 1Institute of Inorganic Chemistry, TU Bergakademie Freiberg, D-09599 Freiberg, Germany
2Institute of Materials Science, TU Bergakademie Freiberg, D-09599 Freiberg, Germany
Superhard materials based on transition metal nitrides, especially in bulk form, with improved mechanical properties are very important for industrial applications such as steel-cutting and -drilling, in which using of diamond tools is undesirable.
[1] Here we report on the synthesis of
bulk nanocomposites of the types B-N and Ti-(Al-Si)-N and their structure and properties.
The Ti-(Al-Si)-N non-oxide precursors were prepared by pyrolysis of inorganic and organometallic compounds under ammonia, which is followed by high pressure-high temperature (HPHT) densification in a multi anvil press (MAP). Prior to this the pyrolyzed intermediate products were investigated by infrared and RAMAN spectroscopy, thermal gravimetric analysis, element analysis, and powder X-ray diffraction. Ultrahard BN-nanocomposites were synthesized from hexagonal BN (h-BN) using direct high-pressure conversion.
organometallic Ti-(Al-Si)-N -precursors → polymers → HPHT →
hard ceramic nanocomposites
h-BN → HPHT → superhard c-BN/w-BN/h-BN-nanocomposites
The obtained bulk nanocomposites were characterized by X-ray diffraction, high-resolution transmission electron microscopy, microhardness and fracture toughness testing and elastic modulus measurement. The information about the phase composition of the nanocomposites, the crystallite size and the atomic ordering at the interfaces between individual nanocrystallites was obtained by microstructural investigations.
[2,3] BN
nanocomposites with 3-4 wt % of the remaining h-BN phase showed the highest Vickers hardness HV0.5 of 65 GPa, higher than that of BN single crystals.
[1] S. Veprek, M.G.J. Veprek-Heijman, P. Karvankova, J. Prochazka, Thin Solid Films 2005 476, 1.
[2] D. Rafaja, V. Klemm, M. Motylenko, M. R. Schwarz, T. Barsukova, E. Kroke, D. Frost, L. Dubrovinsky, N. Dubrovinskaia, J. Mater. Res. 2008, 23 (4) 981-993.
*3+ M. Schwarz, T. Barsukova, D. Šimek, M. Dopita, Ch. Lathe, D. Rafaja, E. Kroke, HASYLAB Annual Report 2007, 647-648.
*E-mail of the corresponding author: [email protected] Keywords: Nitride-based Ceramic, Nanocomposite, Syntheses, High Pressure-High Temperature (HPHT)
357
An in situ X-ray absorption spectroscopy study of the solubility of cristobalite-type Si0.8Ge0.2O2 and aqueous speciation of Ge
in hydrothermal conditions
V. Ranieri1, J. Haines1, O. Cambon*1, C. Levelut2, R. Le Parc2, M. Cambon1, J-L Hazemann3
1 Institut Charles Gerhardt de Montpellier, PMOF, UMR5253, Université Montpellier II, cc1504, Place E.Bataillon, F-34095 Montpellier Cedex 5, France
2 Laboratoire des Colloides, Verres et Nanomatériaux, UMR CNRS 5587, Université Montpellier II, cc026, Place E.Bataillon, F-34095 Montpellier Cedex 5, France
3 Institut Néel, département MCMF, CNRS-Grenoble, 25 avenue des Martyrs, B.P.166, 38042 Grenoble cedex 9, France
In the field of piezoelectric materials, quartz is still the most used. However its physical properties are too limited for emerging applications. Structure-properties relationships linking the thermal stability of the α-quartz type phase and physical properties (dielectric, piezoelectric…) to the structural distortion with respect to the β-quartz structure type have been developed for α-quartz homeotypes. Germanium substitution in the quartz lattice is believed to be a promising way to improve these properties.
The growth of single crystal by the hydrothermal method is controlled by the solubility of the species. Because of the great difference of solubility between SiO2 and GeO2, the growth of α-quartz type Si1-xGexO2 single crystals by this method is an ambitious challenge. The method investigated in order to reduce this problem of solubility is the use of a mixed material as a starting species. Cristobalite-type Si0.8Ge0.2O2 was prepared by a thermal treatment. The dissolution of this material in pure water and in sodium hydroxide aqueous solution was studied by in situ X-ray Absorption Fine Structure (XAFS) spectroscopy at the Ge K-edge using a high temperature-high pressure cell. Spectra in both transmission and fluorescence mode were collected in isobaric conditions (150 MPa) up to 475°C. Local atomic structure around Ge has been investigated as a function of the temperature and as a function of the solvent. In pure water, the solubility of the cristobalite-type Si0.8Ge0.2O2 increases with the temperature and the germanium is in four-fold coordination. The dissolution of the material in sodium hydroxide aqueous solution is quite different. Above a certain concentration a complex between germanium and sodium atoms occurs and involves the precipitation of germanates. Under these conditions, the germanium content in the solution decreases even with increasing the temperature. These results show that sodium hydroxide aqueous solution, usually employed for quartz crystal growth, is not well adapted for germanium containing crystals. These results show also that XAFS is a powerful technique to study solubility and speciation under hydrothermal conditions thereby providing key information for the optimisation of crystal growth at high pressure and high temperature.
The authors would like to thank the DGA for financial support under contract N° 05 34 051.
*Email: [email protected] Keywords: EXAFS, hydrothermal, solubility, speciation
358
Single crystal growth of BiMnO3 under high pressure - high temperature
P. Toulemonde1*, C. Darie1, C. Goujon1, M. Legendre1, M. Álvarez-Murga1, V. Simonet1, P. Bordet1, P. Bouvier2 J. Kreisel2
1 Institut Néel, CNRS & Université Joseph Fourier, Grenoble, France 2 LMGP,CNRS, INP Grenoble, France
The interest of physicists for multiferroic materials has grown the last few years, in particular for BiMO3 compositions with M = Fe, Cr, Mn. BiFeO3 can be elaborated by conventional solid state chemistry, but BiCrO3 and BiMnO3 requires high pressure – high temperature (HP-HT) conditions for their synthesis.
These oxides adopt a distorted perovskite structure which can allow, in some cases, the existence of ferroelectricity. For iron the co-existence of anti-ferromagnetism and ferroelectricity below TN = 370°C has been established unambiguously. The situation is not so clear for chromium and manganese based oxides, antiferromagnetic and ferromagnetic below 114 K and 105 K respectively [1]. In the case of BiMnO3, during the last two years, different studies on powders have shown that its space group was not C 2, as determined previously, but probably C 2/c, i.e. a centrosymetric space group which is incompatible with ferroelectricity.
To definitively answer to this question we have synthesized small single crystals of BiMnO3 at HP-HT in a belt apparatus using different flux. These crystals were studied by x-ray diffraction, magnetic measurements and Raman spectroscopy. The results will be presented.
[1] C. Darie, C. Goujon, M. Bacia, H. Klein, P. Toulemonde, P. Bordet, E. Suard, Solid State Science, in press, 2009.
*Email: [email protected] Keywords: high pressure – high temperature synthesis, multiferroic materials, magnetic and electronic properties
359
High pressure synthesis of functionalized boron nitride by doping
T. Taniguchi
National Institute for Materials Science, 1-1 Tsukuba Ibaraki 305-0044 Japan
Among the variety of III-V nitrides, cubic boron nitride (cBN) is known as the simplest compound with wideband gap: Eg = 6.2eV [1]. Recently, it was found that hexagonal boron nitride (hBN) also exhibits attractive potential as a wideband gap semiconductor: Eg = 5.97eV [2]. For the realization of their attractive potential as opto-electric materials, basic study for their intrinsic properties affected by impurity should be important. Some progresses in the synthesis of high purity BN crystals were recently achieved by using Ba-BN as a solvent material [3]. Based upon these schemes for synthesizing the high purity crystals, artificial doping of some element, such as lanthanide (LA), may open the new window of functionalized properties in the opto-electric BN crystals [4]. With the analogy of LA doping in BN crystals, functionalization of alminium nintride (AlN) crystals by effective doping is also interesting issue for their opt-electric application. In this paper, an attempt to control the color centre of BN and AlN single crystals grown under high pressure was described.
Crystal growth and doping experiments for c-BN and h-BN and AlN were performed under high pressure (HP) and high temperature (HT). It was found that addition of LA-fluoride system, such as EuF3, into the growth solvent was effective to fabricate luminous crystals. Optical properties of c-BN:LA (LA=Ce,Gd,Eu,Tb or Sm) crystals exhibit functionalized features by LA in the crystals. With the analogy of LA doping in cBN, doping of Ce and Sm into hBN and also doping of Ce, Eu, Er, and Mn into AlN, were carried out. Comparing the optical properties of cBN:Eu to AlN:Eu, the former exhibits bright spectra near 580 nm which correspond to forbidden 5D0-7F0 transition, while the latter exhibits bright spectra near 620 nm which is normal luminous feature attributed to Eu
3+ doping materials. This suggest that the occupied
site of Eu3+
is different between cBN:Eu and AlN:Eu. Ab-initio calculation of those occupied site and structural analysis by using STEM are applied to characterize the doping features of cBN:Re.
[1] R.H.Wentorf.Jr., J.Chem.Phys., 36,1990(1962). [2] K.Watanabe, et.al, Nataure Mater. , 3,404(2004). [3] T.Taniguchi, K.Watanabe, J.Cryst.Growth, 303,525,(2007). [4] A.Nakayama,et.al,Appl.Phys.Lett,87,211913(2005).
Email: [email protected] Key word: High Pressure Synthesis, Boron Nitride, Optical Properties
360
High pressure synthesis of the perovskite series RCu3Mn4O12: enhancement of the Curie temperature driven by chemical pressure
of R3+ cations (R=La, rare earth)
J. Sánchez-Benítez, M. Retuerto, M.J. Martínez-Lope, J.A. Alonso
Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid, Spain
We have studied some new derivatives of the complex perovskite CaCu3Mn4O12 [1,2]. Ca2+
cations can be replaced by rare earths in the RCu3Mn4O12 (R = rare earths) family, implying an electron doping effect that dramatically affects the magnetic properties. These compounds must be prepared under high pressure conditions. We have synthesized for the first time, at 2 GPa in a piston–cylinder press, starting from reactive precursors obtained by wet-chemistry techniques, some new members of the family, with R = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, for which we describe structural and magnetization data. The neutron-absorbing members (R = Sm, Eu, Gd) have been studied by synchrotron radiation diffraction whereas the non-absorbing members have been investigated by neutron powder diffraction. We have found an interesting correlation between the magnetism and the evolution of some subtle structural features across the series. Electron injection upon replacement of Ca
2+ for R
3+
cations in the parent CaCu3Mn4O12 compound leads to a substantial increment of the ferrimagnetic Curie temperature (TC). The room temperature magnetic structure displays a ferrimagnetic coupling between Mn
3+/4+ and Cu
2+ spins; additionally the contribution of the
magnetic moment of the rare earth is very significant for R = Pr, Gd, Tb, Dy and Ho below 100 K, suggesting an antiferromagnetic coupling with the Mn sublattice. An additional effect is provided by the internal pressure of the R
3+ cations upon decreasing in size along the rare-
earth series, from La to Lu: the concomitant compression of the MnO6 octahedral units for the small rare-earth members gives progressively shorter Mn-O distances and improves the overlapping between Mn and O orbitals. This effect promotes the superexchange and the long-range magnetic interactions, thus yielding a substantial increase of TC by 50 K along the perovskite series, reaching a TC value over 400 K for LuCu3Mn4O12. The easiness of their preparation, compared to the Ca parent compound, and the improvement achieved in the properties of interest, namely the Curie temperature and the level of magnetoresistance, makes it possible to propose these materials as candidates for practical applications in spintronics.
[1] J. Chenavas, J.C. Joubert, M. Marezio, B Bochu, J. Solid State Chem. 1975, 14, 25. [2] Z. Zeng, M. Greenblatt, M.A. Subramanian, M. Croft, Phys. Rev. Lett. 1999, 82, 3164.
*Email: [email protected] Keywords: High Pressure Synthesis, Perovskite Oxide, Colossal Magnetoresistance
361
Influence of the nanodiamonds adittion on PDC Properties
G. S. Bobrovnitchii, A. l. Diegues Skury, J. I. Margem*
State University of the North Fluminense, Campos dos Goytacazes-RJ, CEP 28013-602, Brazil
Nanosize or ultra-dispersed diamond particles have been recently used as precursor for the development of a new generation of superhard composites
[1]. Differences in the formation
mechanism of these composites were found as a function of developed residual stress. In the present work, diamond composites were obtained by a compacting method at high pressure, almost hydrostatic, and high temperature conditions. Experiments were conducted inside a toroidal anvil type of high pressure device
[2] with a 13,5 mm concavity installed in a 630 ton
press. Temperatures of 1000 to 1600oC combined with pressures of 6.5 to 7.7 GPa, with
predominance in the axial work direction, were used for compacting. The composites were obtained by the infiltration method, using as starting materials: 48/40 μm-and nano (0,01 to 0,004 μm) diamond particles, provided by FNPC “Altay”, and Si powder as the binder. The samples have a cylindrical shape with 5.0 mm diameter and 4.5 mm height. The characterization indicates density values no grater than 2.86 g/cm
3, a maximum hardness of
30.5 GPa and great homogeneity (Figure 1). These results can be explained by X-ray diffraction and suggest a plastic fragmentation of the larger initial particles. It contributes to an ultra-fine composite results can be explained by X-ray diffraction and suggest a plastic fragmentation of the larger initial particles. It contributes to an ultra-fine composite structure, revealed by the intensity of the lines <003> compared with the lines <111> of diamond. The compression strength of the polycrystalline diamond composites was found to be close to that of natural diamonds.
Figure 1. “Diamond-SiC”-based composite microstructure obtained via HPHT with additions of nanodiamonds, in which: diamonds – dark regions; SiC – gray; free Si – white.
[1] Shulzhenko A.A., Bochechko A.A., Oleinik G.S., Gargin V.G., Romanko L.A. et al., J. Superhard Materials. 5, 29, 2001.
[2] L.F. Verestshagin, L.G. Khvostantsev. Patent of USA 38554854 B30b 11/32. Pub. 17/12/1974.
*Email: [email protected] Keywords: High pressure, synthesis, diamond, composites
362
The morphology and diamond properties synthesized in the Mg-Ni–C system
G. S. Bobrovnitchii, A. J. Sideris Jr, A. L. Diegues Skury*
State University of the North Fluminense, Campos dos Goytacazes-RJ, CEP 28013-602, Brazil
Diamonds synthesized from the Mg-C and Zn-C systems at high pressure and high temperature conditions were found to present semi-conducting properties[1]. In these cases, severe synthesis processing parameters such as 8.0 – 8.5 GPa and 1800 – 2100°C are required. Under conditions, diamond particles with cubic morphology can be obtained. In this work, a novel Mg-Ni-C system was used to allow for relatively lower values of synthesis parameters[2]. The precursor Mg-Ni alloy was initially produced by the sintering (at 4.0 GPa and 1300°C) of a Mg and Si powders mixture. The products obtained were stoichometric mixtures of intermetallic solutions with compositions varying from 0,89 at % Mg+ 0,11 at % Ni to 0,23 at % Mg+ 0,77 at % Ni. The diamond synthesis was afterwards conducted under processing conditions of only 6.0 – 7,0 GPa and 1500 – 1800°C inside a toroidal anvil type of high pressure device installed in a 630 ton press[3]. Semi-conducting diamond was obtained
with particle size ranging from 40 to 250 m from Mg2Ni, MgNi2 and 0,23 at % Mg+ 0,77 at % Ni alloys. The best results were obtained under pressures of 6.0 to 6.5 GPa, temperatures of 1500 to 1600°C and time of 100 s. Some of these particles displayed a cubic morphology typical of sintetic diamonds obtained from the Mg-C or Zn-C systems (Figure 1). The development of this novel system and associated synthesis conditions results in a 23 – 26 % increase in the operational lifetime of the high temperature device.
Figure 1. The cubic morphology of diamond crystals obtained under pressure of 6.0 GPa and
temperature of 1500° C, in presence of MgNi2 (x30).
[1] Shulzhenko A. A., Novikov N.V., Chipenko G.V., J. Superhard Materials, 3, 10 (1988). [2] Bobrovnitchii G.S., Osipov A.S., Sideris A.J., J. of Alloys and Compaunds, 372, 88, (2004). [3 L.F. Verestshagin, L.G. Khvostantsev, L.F., Patent of USA 38554854 ICl B30 b 11/32, publ.
17/12/1974.
*Email : [email protected] Key-words: High pressure, synthesis, diamond, properties.
363
Study of diamonds production for analysis register synthesis parameters
W. da Silva Vianna, G. S. Bobrovnitchii, A. L. Diegues Skury*
State University of the North Fluminense, Campos dos Goytacazes-RJ, CEP 28013-602, Brazil
The diamond synthesis process employ high pressure (P) technique between 4,5 up to 8,0 GPa and high temperature (T) between 1150 up to 2000
oC. This technique use high-pressure
apparatus (HPA), compress solid and special hydraulic press. The syntheses process its non-stable, because variation of properties catalytic base and graphite, density and quality assembly components changes P-T parameters. Besides, the severe process conditions change dimensions and configuration of the compression chamber in HPA. Those variations are responsible for effectiveness diamond production. The stable production, in some cases, it is necessary to correct the parameters during the process. For that end, special power hydraulic press 2500 Ton, model D0044 installed at UENF, it was modernized allowing registration direct and indirect process parameters. The data registrations, allowing analysis for determinate which indirect parameters are influencing about stability P-T parameters process and its effectiveness. The largest influence this linked with irregularities at dimensions container, density at insulating covers, dimensions and density at reactivates mixture, and conditions contact between graphite heating disk and anvil. The analysis of the indirect parameters considering behavior at the direct parameters through programmable command was possible increase diamond productivity up to 70% in system Ni-Mn-C. Besides, they were outstanding some parameters, among them distance between parts HPA, that was possible to elaborate method for determination process effectiveness.
*Email: [email protected] Key-words: production, synthetic diamonds, high pressure, high pressure device.
364
Hydrothermal/solvothermal synhtesis of new hybrid materials with potential applications in nanomedicine
R. M. Piticescu1, G. Demazeau2, R. R. Piticescu1 1 National R&D Institute for Non-ferrous and Rare Metals, Pantelimon-Ilfov, Romania
2 CNRS/ Institut de Chimie de la Matière Condensée de Bordeaux, France
The hydrothermal/solvothermal methods are one of the most efficient procedures allowing the development of new materials consisting of an inorganic phase and an organic component (polymeric, bio-molecules) at moderated temperatures and high pressures. The precise control of the parameter pressure is able to induce chemical covalent bonding between the functional organic groups and inorganic radicals while the moderate working temperatures avoid thermal destruction of the organic phase. In the same time the low temperatures and high pressure conditions induce the nucleation of inorganic phase as high reactive nanocrystalline particles.
The paper presents the hydrothermal synthesis of two types of hybrid nanostructured materials with potential applications in nanomedicine:
- hydroxyl apatite and derivates of maleic acid - zinc oxide and poly-methil-metacrilate
The new hybrid nanostructured materials are characterised by FT-IR, UV-VIS and DSC methods.
[1] G. Demazeu, G. Goglio, A. Denis, A. Largeteau, J. Phys. Condensed Matter, vol. 14 (2002) pp 11085-11088
[2] Y. Rigaldie, G. Demazeau, Ann. Pharm. Fr., vol. 62, 2004, p. 116-127 [3] G. Demazeau, J. Mater. Sci. 43,2104(2008) [4] R.M.Piticescu, G. Demazeau, L.M. Popescu, COST D30 Final Meeting, 26-27 October 2007,
Bordeaux, France [5] R.M.Piticescu, L.M.Popescu, M. Giurginca, C.G. Chitanu, G. Negroiu, Journal of
Optoelectronics and Advanced Materials, 9(11) (2007), 3354-3357
*Email: [email protected] Keywords: hydrothermal synthesis, hybrid materials, nanomedicine
365
Extrusion-activated thermal explosion applied to intermetallics processing
M. Andasmas*1, D. Vrel1, N. Fagnon1, Th. Chauveau2, A. Hendaoui3, P. Langlois1 1 CNRS LIMHP, Université Paris 13, Villetaneuse, France
2 CNRS LPMTM, Université Paris 13, Villetaneuse, France 3 LEREC, Université Badji Mokhtar, Annaba, Algeria
Intermetallics form a class of materials whose properties make it range between those of metals and ceramics. They indeed exhibit properties such as high-temperature strength, high thermal conductivity, good oxidation resistance at high temperature, and low density. Their well-known representatives include replacement pieces or coatings for stainless steels or superalloys in automotive and aerospace applications, magnetic and superconducting materials, and shape memory alloys. A major drawback, yet limiting their use, relates to their high cost of processing.
We focused on producing intermetallics in the Ni-Al system, especially the Ni3Al and NiAl compounds a.k.a. nickel aluminides, through the thermal-explosion route akin to self-propagating high-temperature synthesis (SHS). Either route has the potential for addressing the cost problem and both reactions may alike be significantly enhanced by prior activation. In the case of SHS, this step relates to mechanical activation based on preparation methods, such as ball milling which causes the oxide layers to break and the diffusion distances to decrease, that increase the reactivity of the mixture, the maximum temperature of the combustion wave, and its propagation velocity
[1].
The current presentation emphasizes the extrusion-related activation that thermal explosion benefited from. Both reactant powders were previously homogeneously mixed and subsequently precompacted by cold isostatic pressing (CIP) up to 2 GPa. Hydrostatic extrusion was specifically performed on selected samples with a low applied back-pressure, fixed at 50 MPa whereas extrusion pressures ranged from 350 MPa to 1.4 GPa, yielding a fully dense Ni+Al mixture, hence maximizing the contact areas between the reactants, with little (if any) grain refinement conversely to mechanically activated SHS. After reaction under optimal conditions compared to those leading to either fully dense but poorly reacted materials, under the circumstances of solid-state diffusion, or fully reacted but porous ones, we obtained fully-reacted, dense materials, exhibiting extrusion-related crystallographic textures. Effects of pressure were also considered in terms of induced hardness. Due to the ability of reputedly brittle materials to deform when hydrostatically contained, both CIP and hydrostatic extrusion, which have previously been operated on metals and ceramics
[2-3], could
also prove suitable for forming intermetallics in regard to their lack of ductility at room temperature.
[1] Ch. Gras, E. Gaffet, F. Bernard, D. Vrel, J.-C. Niepce, J. Alloy. Compd. 2001, 314, 240. [2] Y. Champion, S. Guérin-Mailly, J.-L. Bonnentien, P. Langlois, Scripta Mater. 2001, 44, 1609. [3] S. Nhien, P. Langlois, H. Massat, J. Wang, G. Desgardin, M. Lepropre, J. Provost, Physica C
1994, 235-240, 3403.
*Email : [email protected] Keywords : Powder Metallurgy; Extrusion; Densification; Intermetallics.
366
High Pressure Chemistry of C-N-H Systems: Results from the Laser-Heated Diamond Anvil Cell
A. Salamat, P.F. McMillan, R. Quesada Cabrera, K. Woodhead, A. Rahman, F. Cora
University College London, Christopher Ingold Laboratories, 20 Gordon St, London WC1H 0AJ
Since the theoretical prediction that sp3-bonded forms of carbon nitride (C3N4) might be
superhard [1, 2] there has been intense interest in developing high-density materials within the C-N-H system. Such compounds could also have applications for energy storage [3]. Analogous compounds include refractory ceramics based on Si3N4 [4]and Ga, Ge-containing nitrides that provide wide bandgap materials for optoelectronics applications. High-pressure, high-temperature (HPHT) synthesis experiments have resulted in novel spinel-structured forms of Si3N4 [5] and Ga3O3N [6] with high hardness, low compressibility and wide electronic bandgaps. Various dense CxNy materials have been produced but their structures, properties and chemical compositions have not been fully determined .
The work presented here is of our investigations into the synthesis and recovery of new materials within two C-N-H systems, C2N3H [7] and C6N9H3.HCl. Crystallographic analysis of these systems is a challenging process, made more difficult by their light elemental composition and the use of the diamond anvil cell. For both systems a systematic experimental and analytical strategy was adopted to enable the extraction of the best data possible, both qualitatively and statistically.
The synthesis of a new sp3-bonded carbon nitride material C2N3H is discussed with a structure
related to wurtzite. Metastable phases of this new compound are identified during the intermediate stages of synthesis and we go on further by suggesting that the synthesis of C2N3H implies a possible formation route to the predicted superhard material C3N4. Furthermore, a layered graphitic CxNy system with composition C6N9H3.HCl is described and following laser heating in the DAC details of a further novel dense carbon nitride phase will be given as supported by ab initio calculations.
[1] A. Y. Liu, and M. L. Cohen, Science 245 (1989). [2] D. M. Teter, and R. J. Hemley, Science 271, 53 (1996). [3] X. C. Wang, K. Maeda, A. Thomas, K. Takanabe, G. Xin, J. M. Carlsson, K. Domen, and M.
Antonietti, Nature Materials 8, 76 (2009). [4] R. Riedel, Wiley, John & Sons, Inc 1 (2008). [5] E. Soignard, M. Somayazulu, J. Dong, O. F. Sankey, and P. F. McMillan, J. Phys. Condens.
Matter 13, 557 (2001). [6] I. Kinski, G. Miehe, G. Heymann, R. Theissmann, R. Riedel, and H. Huppertz, Z.
Naturforsch., B: Chem. Sci 60, 831 (2005). [7] E. Horvath-Bordon, R. Riedel, P. F. McMillan, P. Kroll, G. Miehe, P. A. v. Aken, A. Zerr, P.
Hoppe, O. Shebanova, I. McLaren, S. Lauterbach, E. Kroke, and R. Boehler, Angew. Chem. Int. Ed. 46, 1476 (2007).
Email : [email protected]
367
Author Index
A
Abagaro B.T.O. · 111 Abd-Elmeguid M.M. · 269, 270 Abdullaev A.A. · 253 Abe H. · 194 Abe J. · 147 Abouelsayed A. · 210 Abraini J.H. · 101 Abrikosov I.A. · 41, 48, 232 Achary S. N. · 150 Acquilanti G. · 313 Adams A.R. · 263, 264 Aertsen A. · 114 Aguado F. · 181 Aguiar A.L. · 223 Ahuja R. · 44 Alario-Franco M.Á. · 286, 350 Alfé D. · 46 Alibekov A.G. · 253, 353 Alonso J.A. · 360 Alonso M.I. · 260 Alpas H. · 73, 77 Álvarez-Murga M. · 307, 358 Al-Zein A. · 262 Amann M.C. · 264 Amenitsch H. · 100 Amiguet E. · 183 Amulele G. · 120 Andasmas M. · 365 Andrault D. · 172, 186, 348 André G. · 317 Andreev A.V. · 282 Andreev E.V. · 258 Angilella G.G.N. · 225 Angulo I. · 80 Antonangeli D. · 168 Aoki K. · 300, 301 Aparicio C. · 336 Aquilanti G. · 142, 149, 161, 341 Arakawa M. · 147 Arapan S. · 44 Archer J. · 162 Arévalo-López A.M. · 286, 350 Arima H. · 147 Arnold Z. · 287, 309, 310 Arslanov R.K. · 252, 254, 255, 256
Arslanov T.R. · 252, 254, 255 Arvanitidis J. · 219 Ascone I. · 102 Attfield J.P. · 157 Avdonin V.V. · 215 Ayari A. · 209 Ayrinhac S. · 185
B
Babushkin A.N. · 212, 222, 249, 353, 354, 355 Bachelet C. · 134 Bachmann A. · 264 Badro J. · 168 Bailey E. · 114 Baldassarre L. · 279, 290, 302 Ballestra P. · 82, 89 Baranov A.N. · 263, 338 Barbosa L. · 100 Barla A. · 270 Barros E.B. · 223 Barsukova T. · 356 Basavapoornima Ch. · 125 Bashkin I.O. · 297 Batisse R. · 133 Bauchau S. · 148 Baudelet F. · 316 Bażela W. · 312 Béjina F. · 184 Belandria E. · 217 Belliard L. · 243 Beloshenko V. · 311 Beltrán A. · 54 Benoit J.-M. · 209 Benzaria A. · 91 Bergara A. · 42 Berghäuser A. · 141 Berman I.V. · 258 Betranhandy E. · 47 Bezruchko G.G. · 123 Bezruchko G.S. · 124 Bhalerao G.M. · 265 Bielemeier B. · 308 Bindrich U. · 94, 95 Bobrovnitchii G.S. · 361, 362, 363 Bocian A. · 158 Boehler R. · 121, 142 Boffa Ballaran T. · 182
368
Bogdanov E.V. · 258 Boiron J.M. · 105, 107 Bolfan-Casanova N. · 172 Bolzoni F. · 317 Bonev S. · 45 Bonneté F. · 101 Boon N. · 334, 340 Bordet P. · 317, 358 Borodina T.I. · 218 Bouamrane F. · 134 Boukari C. · 134 Bourée F. · 317 Bouvet T. · 134 Bouvier P. · 155, 277, 358 Bove L.E. · 192 Bozoğlu F. · 73, 77 Brabers V.A.M. · 290 Brazhkin V.V. · 193 Briottet L. · 133 Bromiley G. · 164 Broto J.M. · 217, 244, 294 Bruyère R. · 126 Brygoo S. · 119 Bull C.L. · 143, 156, 158, 162, 198, 199, 200 Bulou A. · 120 Burchard M. · 134 Bureau H. · 134, 135 Butz P. · 70 Buzrul S. · 73 Bystricky M. · 184
C
Cabassi R. · 317 Caillier C. · 209, 223 Calamiotou M. · 289 Calestani G. · 317 Calicchio M. · 317 Cambon M. · 357 Cambon O. · 327, 357 Cao H. · 275 Caporiccio B. · 91 Caracas R. · 182 Cardona M. · 240, 246 Carlsson S.J.E. · 318, 343 Carrier H. · 324 Casper F. · 273 Cassiède M. · 136 Castillo-Martínez E. · 286 Cava R.J. · 273 Cazorla C. · 46 Celliers P. · 119
Chagnot S. · 242 Chakoumakos B.C. · 191 Champion Y. · 224 Chauveau Th. · 365 Chen J. · 183 Chen Y.P. · 322 Chernyshov D. · 232 Chervin J.C. · 56, 132, 134, 135, 236, 250 Chevalier-Lucia D. · 90 Chien S.Y. · 164 Chigarev N. · 120 Chishko T. · 311 Chow P. · 342 Christofilos D. · 219 Chumakov A. · 178 Claessen R. · 278, 290 Clarke S. · 305 Cohen M.L. · 239 Colin C.V. · 310 Collins G. · 119 Colloc’h N. · 101, 103 Conder K. · 289 Congeduti A. · 152, 242, 339 Coppari F. · 242 Cora F. · 366 Cordier P. · 34, 144, 160, 183 Cortés-Muñoz M. · 90 Coulet J.P. · 80 Couzinet B. · 134, 135 Crichton W. · 182, 277, 305 Cruz C. · 89
D
D’Astuto M. · 316, 318 da Silva Vianna W. · 363 Dance P. · 334 Daniel I. · 186 Daridon J.L. · 136, 324 Darie C. · 358 Darkrim Lamari F. · 133 Darracq S. · 321, 327 Datchi F. · 134, 190 Daunov M.I. · 256 de Lamballerie M. · 66 De Sousa G.P. · 109, 110 Débord R. · 226 Decremps F. · 243 Deglint E. · 340 del Corro E. · 122 Delbecq L. · 134 Delgado A. · 68, 69, 84
369
Demazeau G. · 80, 82, 89, 105, 107, 276, 321, 326, 327, 364
Demidov V.S. · 146 Dera P. · 171, 180 Dewaele A. · 231 Dewitz C.V. · 244 Dhaussy A.C. · 101, 102 Di Castro D. · 279 Di Cicco A. · 242 Diegues Skury A.L. · 361, 362, 363 Dinh V. · 334 Diviš M. · 272 Dizhur E.M. · 314 Dkhil B. · 277 Dmitriev V. · 99, 232 Dobromyslov A.V. · 175, 233 Dorogokupets P.I. · 59 Dos Santos-García A.J. · 286, 350 Downs R.T. · 180 Dragoe N. · 339 Drulis H. · 282 Dubrail J. · 186 Dubrovinskaia N. · 41, 232 Dubrovinsky L.S. · 41, 153, 178, 182, 232, 284,
285, 299 Dudin S.V. · 146 Dulin F. · 101 Dumas P. · 257 Dumay E. · 90, 91 Dunstan D.J. · 207 Durán A. · 286 Dyakonov V. · 311, 312
E
Ebad-Allah J. · 290 Edwards E. · 340 Efthimiopoulos I. · 196, 230, 251, 274 Eggert J. · 119 Ehm L. · 191 Ehnes A. · 141 El Moueffak A. · 82, 89 Eremets M.I. · 131, 234, 273, 281 Errandonea D. · 54, 56, 150, 247, 248, 250 Errea I. · 42 Evers J. · 234
F
Fagnon N. · 133, 365 Fainstein A. · 260
Fang J. · 156 Farber D.L. · 168 Feder J.G. · 106 Felser C. · 273 Fernández A. · 70 Fernández- San Julian J. · 350 Fernandez-Diaz M.T. · 162 Ferrer-Roca C. · 257 Filinchuk Y. · 232 Finet S. · 101 Fiquet G. · 168 Flahaut E. · 217 Flank A.M. · 315 Fons P. · 241 Foret M. · 185 Forget A. · 275 Fortes A.D. · 193 Forthaus M. · 270 Fortov V.E. · 146, 215, 288 Fourme R. · 101, 102 Foy E. · 135 Frączek Z.J. · 306 Frank S. · 278, 283 Franz H. · 141 Fraysse G. · 262 Freire P.T.C. · 109, 110, 111, 127 Frost D. · 177, 349 Fuentes-Cabrera M. · 248 Funakoshi K. · 154, 174
G
Gajda D. · 311 Gantis A. · 289 Garanin V.A. · 337 Garbarino G. · 148, 284, 305, 307 García-Baonza V. · 122, 336 Gauthier M. · 243, 265 Gautron L. · 186 Gauzzi A. · 317, 318, 343 Geenen T. · 183 Ghandour A.J. · 207 Giacomazzi L. · 49, 50 Giaever I. · 106 Giffard M. · 101 Gilioli E. · 317, 318 Gillan M.J. · 46 Giordano V.M. · 190 Girard E. · 101, 102 Girard J. · 183 Giriat G. · 128, 130 Girodon-Boulandet N. · 133, 224
370
Glawion S. · 278 Glazyrin K. · 178, 299 Golubev A.A. · 146 Golyshev A.A. · 235 Gomis O. · 248 Goncharenko I.N. · 275, 291 Goncharov A. F. · 117 Gondé C. · 134 Goñi A.R. · 260 González J. · 208, 217, 220, 244, 294, 295 Goto M. · 328 Goto T. · 194 Goujon C. · 126, 358 Gouttenoire V. · 209 Gracia L. · 54 Gréaux S. · 186 Greenberg E. · 284 Gregoryanz E. · 162, 198 Gritzner G. · 287, 292 Gromnitskaya E.L. · 193 Grott M. · 170 Grześkiewicz A. · 78, 79, 81 Guamis, B. · 72 Guamis-López B. · 92 Guennou M. · 155, 277 Guerini S. · 211 Guignon B. · 336 Guillaume C. · 349 Gusev V. · 120 Guthrie M. · 143, 162, 198, 200 Gutmann M.J. · 143 Guyon C. · 66
H
Haines J. · 241, 262, 348, 357 Hamel G. · 164 Hamidov H. · 143, 162, 200 Hammouda T. · 348 Hanfland M. · 151, 196, 230, 241, 251, 274,
278, 283, 284 Hansen T.C. · 192 Haskel D. · 271 Hatami F. · 244 Hattori T. · 147 Haumont R. · 277 Hazael R. · 114 Hazemann J.L. · 357 Hébert P. · 137, 348 Hector A. · 341 Heinz V. · 67, 94, 95 Hendaoui A. · 365
Hennrich F. · 210 Hernandez-Herrero M.M. · 92 Heroldova M. · 71, 74, 76 Hewener B. · 178 Hidalgo E. · 336 Hirao N. · 300 Ho J. · 179 Hodeau J-L. · 213 Hoffmann H. · 278 Hoke K. · 75 Honzova S. · 71, 74, 76 Horn S. · 278, 283 Houska M. · 71, 74, 75, 76 Huotari S. · 316 Huppertz H. · 36 Huppertz T. · 65 Hussmann H. · 170 Huxley A. · 159
I
Ikyo A.B. · 264 Imai Y. · 194 Ingrin J. · 184 Isambert A. · 137, 348 Isnard O. · 309, 310 Itié J.P. · 163, 315, 339 Ivanovic Z. · 105, 107 Iwasa Y. · 219
J
Jankowska A. · 78, 79, 81 Jaque D. · 296 Jastrzębski C. · 86 Javorský P. · 304 Jayasankar C.K. · 125 Jeanloz R. · 119 Jeffree C.E. · 349 Jeworrek C. · 104 Johnson M.W. · 143 Jourdain V. · 209 Jovanovic J. · 68 Jurczak J. · 331 Jurga W. · 202, 203 Jyothi L. · 125
371
K
Kadyrova N.I. · 354 Kagayama T. · 229, 301 Kagi H. · 147 Kahn R. · 101, 102 Kamarád J. · 282, 287, 304, 309, 310 Kamarás K. · 210 Kamenev K.V. · 128, 130, 156, 157, 158, 159 Kamilov I.K. · 252, 254, 255 Kandrina Y.A. · 249 Kanel G.I. · 123, 124 Kaneshige M. · 229 Kantor A. · 153, 171 Kantor I. · 153, 171, 176, 285 Kantsyrev A.V. · 146 Karmakar S. · 196, 230, 251, 274 Kashani-Shirazi K. · 264 Kataura H. · 219 Katrusiak A. · 344 Keen D.A. · 348 Keese C.R. · 106 Kelly A.L. · 65 Kheifets O.L. · 353, 355 Khishchenko K.V. · 60, 61, 123, 124 Kikegawa T. · 154 Kim D. · 257 Kim J.S. · 274 Kimura N. · 303 Kissel H. · 258 Klapötke T.M. · 234 Klemm M. · 278 Klotz S. · 132, 164, 192 Klug D.D. · 191 Kminkova M. · 71, 74, 76 Knorr D. · 67 Kohara S. · 348 Kolesnikov S.A. · 146 Kolobov A.V. · 241 Kolokolov K.I. · 258 Komarovskii I.A. · 261 Komatsu K. · 143, 147, 162, 200 Konopkova Z. · 117 Konstantinova T. · 311 Kościesza R. · 83, 84, 85, 86 Kostyleva I.E. · 314 Kourouklis G. A. · 219 Kozlenko D.P. · 37, 291 Kozlov E.A. · 175, 233 Kravchenko Z. · 312 Krbal M. · 241 Kreisel J. · 155, 277, 358 Kremer R.K. · 274
Kroke E. · 356 Krupski M. · 202, 203 Ksenofontov V. · 273 Kubsky S. · 134, 135 Kucera P. · 71, 74, 76 Kulisiewicz L. · 69, 84 Kunc K. · 196 Kuntscher C.A. · 210, 278, 283, 290 Kurakevych O.O. · 335, 352 Kurnosov A. · 284 Kýhos K. · 75
L
Labrador H. · 324 Lacomba-Perales R. · 56, 150, 247, 250 Lagarde P. · 315 Lakatos D. · 112 Lampakis D. · 289 Landfeld A. · 75 Lange R. · 101, 103 Langenhorst F. · 177 Langlois P. · 133, 224, 365 Largeteau A. · 80, 82, 89, 105, 107, 321, 327 Lathe C. · 338 Lauck R. · 240 Laurenczy G. · 332 Lavín V. · 296 Lavina B. · 180 Lavrova G.V. · 306 Lazor P. · 117 Le Bail A. · 66 Le Bolloc’h D. · 163 Le Floch S. · 209 Le Godec Y. · 164, 318, 343 Le Marchand G. · 132, 236 Le Parc R. · 241, 357 Lee M.S. · 197 Lee S. · 291 Legendre M. · 126, 358 Lejay P. · 305, 307 Lemmens P. · 251 Lemos V. · 111, 211 Leon-Luis S.F. · 296 Lerche M. · 271 Levashov P.R. · 60 Levelut C. · 241, 348, 357 Liarokapis E. · 289 Liebermann R.C. · 167 Liermann H.P. · 141 Lima Jr J.A. · 109, 111 Lin C.T. · 274
372
Liu C. · 303 Liu J. · 182 Lo Nigro G. · 172 Loa I. · 198 Lonzarich G.G. · 303 López S. · 57, 58, 247 López-Pedemonte T.J. · 92 López-Solano J. · 43, 53 Loubeyre P. · 119, 201, 231 Loupias G. · 318 Loveday J.S. · 143, 156, 158, 162, 198, 199, 200 Lundegaard L.F. · 198, 200 Lupi S. · 279, 302 Luz-Lima C. · 110, 127 Lyakhov A. · 281 Lyapin A.G. · 193
M
Ma Y. · 281 Machida A. · 300, 301 Machmudah S. · 328 Machon D. · 214, 223 Makida H. · 323 Malavasi L. · 279 Manjón F.J. · 248 Marassio G. · 101 Marchal S. · 101, 103 Marenkin S.F. · 252, 253, 254, 255 Marezio M. · 317 Margem J.I. · 361 Margiolaki I. · 289 Mariani P. · 100 Marini C. · 279 Marko I.P. · 263, 264 Marques L. · 213 Marquina J. · 208 Martin C.D. · 191 Martinez E. · 257 Martínez-García D. · 56, 164, 250 Martínez-Lope M.J. · 360 Martín-Rodríguez R. · 220 Marzouki S. · 66 Masselink W.T. · 244 Mathis Y.L. · 251 Mathon O. · 149, 161, 316 Mathys A. · 67 Matrosov N. · 311 Matsuoka T. · 229, 300, 301 Maurel J.P. · 105, 107 Maynard-Casely H.E. · 169, 198, 199 Mayot H. · 309, 310
McCammon C. · 178, 285, 299 McGaff A.J. · 349 McMahon M.I. · 198, 199, 200 McMillan P.F. · 99, 114, 341, 366 McQueen T.M. · 273 Medvedev S.A. · 234, 273, 281 Meersman F. · 99, 114 Meijer J. · 134 Melnikova N.V. · 353, 354, 355 Melo F.E.A. · 109, 110, 111 Mendes Filho J. · 109, 110, 111, 127 Merkel S. · 144, 160 Mezouar M. · 101, 148, 164, 172, 213, 231,
305, 307, 343, 349 Mezzadri F. · 317 Michiels C. · 114 Mihalik M. · 287, 292 Mikhaylushkin A.S. · 41, 48, 232 Millot M. · 217, 244, 294 Milyavskiy V.V. · 123, 218 Ming L.C. · 120 Minina N.Y. · 258 Mintsev V.B. · 146 Mirebeau I. · 275, 291 Míšek M. · 272, 304 Mitróová Z. · 292 Mitsui T. · 300 Mochalova V.M. · 333, 337 Mollaev A.Y. · 252, 253, 254, 255, 256, 353 Molodets A.M. · 215, 216, 235, 288 Monaco G. · 316 Monza A. · 316 Morgenroth W. · 141 Morniroli J.P. · 349 Motylenko M. · 356 Moudrakovski I.L. · 191 Muffler K. · 178 Mujica A. · 55, 56 Muniz L.R. · 260 Muñoz A. · 43, 51, 52, 53, 55, 56, 57, 58, 152,
247, 248, 257 Muñoz M. · 161 Muñoz Ramo D. · 173 Muñoz-Santiuste J.E. · 296 Munro A. · 103 Munsch P. · 132, 134, 135, 190, 236
N
Naghavi S. · 273 Nakagawa Y. · 301 Nakamoto Y. · 229, 301
373
Nakano S. · 221 Nakayama A. · 221 Nanot S. · 217 Narygina O.V. · 178, 285 Nataf L. · 295 Needs R.J. · 55 Nelmes R.J. · 143, 156, 158, 162, 198, 199, 200 Nicol M. · 180 Nicolas F. · 134 Nicolle J. · 214 Ninet S. · 201 Nishiyama Y. · 221 Nisr C. · 144 Nohara M. · 303 Novotna P. · 71, 74, 76 Novotorzev V.M. · 252, 254, 255 Nugyen H. · 301 Núñez Regueiro M. · 305, 307
O
Obermeier G. · 283 Obraztsova E. · 222 Occelli F. · 119 Odling N. · 349 Oganov A.R. · 281 Ohishi Y. · 229, 300, 301 Ohtaka O. · 154 Okuchi T. · 147 Olejniczak A. · 344 Ollivier J. · 100 Onoda S. · 229 Orlowska M. · 66 Ortore M.G. · 100 Osváth S. · 113 Ovsyannikov S.V. · 129, 236, 261
P
Paciaroni A. · 100 Paillet M. · 209 Paillol J.H. · 136 Palasyuk T. · 234, 273 Palenzona A. · 305 Papet Ph. · 262 Paraguassu W. · 127 Parise J.B. · 191 Park J.G. · 291 Pascarelli S. · 149, 161, 313, 316, 341 Pashkin A. · 278, 283 Pasternak M.P. · 280, 284
Pauly J. · 136 Paurá E.N. · 211 Pellegrino F.M.D. · 225 Pellicer-Porres J. · 152, 257 Perez J. · 101 Pérez-González E. · 51, 52, 248 Perrillat J.P. · 148, 164, 169, 172 Perrin B. · 243 Pertierra P. · 122 Perucchi A. · 279, 302 Petitet J.P. · 137 Philippe J. · 164 Phillips R. · 103 Picher M. · 209 Pickard C.J. · 33 Pinsard-Gaudart L. · 339 Pischedda V. · 226 Piticescu R.M. · 364 Piticescu R.R. · 364 Plaindoux P. · 126 Polian A. · 56, 152, 163, 185, 236, 242, 250,
265, 315 Poncharal P. · 214 Ponomarieva V.G. · 306 Ponosov Yu.S. · 293 Ponyatovsky E.G. · 297 Popescu C. · 339 Postorino P. · 279, 302 Power Ch. · 217 Pradel A. · 241 Prakapenka V. · 153, 171, 176, 232, 281 Prangé T. · 101, 102 Prat A. · 126 Pravica M. · 342 Prchal J. · 272 Principi E. · 242 Prokleška J. · 304 Proskova A. · 71, 74, 76 Pruuel E.R. · 218 Ptasznik S. · 87 Pucci R. · 225 Pugh E. · 303
Q
Quesada Cabrera R. · 99, 366 Quynh L.M. · 113
R
Rabia K. · 283
374
Radescu S. · 55, 56 Rafaja D. · 356 Rahman A. · 366 Ranieri V. · 327, 357 Raptis C. · 259 Ratcliffe C.I. · 191 Raterron P. · 183 Raty J.Y. · 45 Rauh C. · 68, 69 Ravy S. · 163, 315 Razorenov S.V. · 123, 124 Recio J. M. · 122 Redfern S.A.T. · 164, 181 Reimer S. · 179 Reineke K. · 67 René-Trouillefou M. · 91 Reparaz J.S. · 260 Reps A. · 78, 79, 81 Retuerto M. · 360 Ribarik G. · 144 Ribes M. · 241 Ripmeester J.A. · 191 Rivalain N. · 105, 107 Rivers M.L. · 171 Rodríguez F. · 181, 208, 217, 220, 276, 294, 295 Rodríguez J. · 276 Rodríguez-Hernández P. · 43, 51, 52, 53, 56, 57,
58, 247, 248, 257 Rodríguez-Mendoza U.R. · 296 Roig-Sagués A.X. · 92 Romero A.H. · 57, 58, 247 Roquain J. · 105, 107 Rostocki A.J. · 86, 87, 88 Rouquette J. · 262 Rousse G. · 317, 318 Rousseau B. · 42 Rozas G. · 260 Rozenberg G.Kh. · 280, 284 Rueff J.P. · 316 Rueffer R. · 270 Rufflé B. · 185 Ruffoni M. · 161 Ruiz-Fuertes J. · 150, 247, 248 Rupprecht K. · 308 Russell N. · 349 Russo D. · 100 Ryerson F.J. · 168
S
Sabino A.S. · 110 Saipullaeva L.A. · 353
Saitta A.M. · 190, 192, 257 Salamat A. · 366 Salvadó M. A. · 122 Sampathkumaran E.V. · 308 San Miguel A. · 209, 214, 223, 226 Sánchez-Benítez J. · 360 Sanloup C. · 169 Sanz P.D. · 336 Sanz-Ortiz M.N. · 276 Saraiva G.D. · 127 Saravanan S. · 260 Sasaki M. · 328 Sauvajol J.-L. · 209 Savenko B.N. · 291 Savinykh A.S. · 123, 124, 216 Saypulaeva L.A. · 253 Scandolo S. · 49, 50, 189, 197 Schmidt M. · 270 Schollenbruch K. · 177, 299 Schönleber A. · 278 Schroeder J. · 106 Schünemann V. · 178 Schwarz M.R. · 356 Schwegler E. · 45 Sechovský V. · 272, 304 Segura A. · 150, 152, 247, 257 Sellam A. · 318 Serghiou G. · 349 Setinova I. · 71, 74, 76 Shakhray D.V. · 216, 288 Shakirov E.F. · 355 Sharkov B.Y. · 146 Shchennikov Jr V.V. · 261 Shchennikov V.V. · 129, 261 Shen G. · 180, 271 Shih B. · 240 Shilov G.V. · 215 Shimizu K. · 229, 301 Shimono M. · 154 Shirokov S.S. · 258 Shukla A. · 316, 318 Shulga Yu.M. · 215 Sibley L.A. · 303 Sideris Jr A.J. · 362 Siebert J. · 168 Siegoczyoski R.M. · 83, 85, 86, 88 Sievers W. · 125 Simak S.I. · 41, 48, 232 Simon G. · 134, 135 Simonet V. · 358 Simonin H. · 66 Sing M. · 278, 290 Sinogeikin S. · 153 Siranidi E. · 289
375
Sjakste J. · 47, 245 Smeller L. · 93, 112, 113 Smirnov G.N. · 146 Sohl F. · 170 Sokolov D.A. · 159 Sokolov P.S. · 338 Solozhenko V.L. · 164, 335, 338, 347 Somogyi A · 135 Song K. · 68 Sosikov V.A. · 325 Souta-Neto N. · 271 Souza Filho A.G. · 127, 223 Sow A. · 307 Spinozzi F. · 100 Spuskanyuk V. · 311 Stankowski J. · 202, 203 Stavrou E. · 259 Stixrude L. · 173 Strässle Th. · 192 Strobel P. · 307 Strohalm J. · 71, 74, 75, 76 Strohm C. · 270, 313 Struzhkin V.V. · 117 Sturhahn W. · 271 Stüsser N. · 312 Suleimenov Y.M. · 328 Sulpice A. · 307 Sundqvist B. · 226 Suresh N. · 157 Suslick K.S. · 271 Sutton S.R. · 171 Suzuki A. · 154 Sweeney S.J. · 263, 264 Syassen K. · 196, 230, 251, 259, 274 Szigeti K. · 112 Szymczak H. · 312 Szytuła A. · 312
T
Takagi H. · 303 Takashima S. · 303 Takekiyo T. · 108, 194 Takemura K. · 118, 300 Takenobu T. · 219 Tallman R.E. · 240 Taluts N.I. · 175, 233 Tamblyn I. · 45 Tanaka Y. · 221 Taniguchi T. · 359 Tarakowski R. · 88 Taravillo M. · 122
Tauscher B · 70 Taverna D. · 318 Tebenkov A.V. · 355 Tefelski D.B. · 85, 86, 87 Teissier R. · 263 Ten K.A. · 218 Tereshina E.A. · 282 Thiele L. · 334 Thirunavukkuarasu K. · 210 Thomson A. · 349 Tiginyanu I.M. · 248 Tikhomirova G.V. · 212 Tintchev F. · 94, 95 Tissen V.G. · 297 Tkachev S. · 342 Toepfl S. · 94, 95 Tokuşoğlu Ö. · 73, 77 Tolochko B.P. · 218 Tomé C. · 160 Tomid S. · 263 Tominaga J. · 241 Torchio R. · 313 Torrent J. · 103 Torrent M. · 231 Torunov S.I. · 337 Toulemonde P. · 305, 307, 358 Trapananti A. · 142, 161 Trojan I.A. · 131, 234, 273, 281 Tröster Th. · 125 Trujillo, A.J. · 72 Tschauner O. · 180 Tschentscher T. · 145 Tsuchiya J. · 186 Tsuchiya T. · 186 Tsurkan V. · 251 Tulk C.A. · 191 Turčínková D. · 272 Turkevich V.Z. · 338 Turtikov V.I. · 146 Tyagi A. K. · 150 Tyagur I. · 298 Tyagur Y. · 298 Tyuterev V. · 245
U
Ungar T. · 144 Uosaki Y. · 323 Ursaki V.V. · 248 Ustinova I.S. · 354 Utkin A.V. · 146, 325, 333, 337, 351 Utsumi W. · 147
376
V
Vaccari M. · 149 Vaccaro P.O. · 260 Vacher R. · 185 Vajenine G.V. · 196, 230 Valiente R. · 208, 217, 220, 294, 295 Valle M. · 281 van Smaalen S. · 232, 278 van Westrenen W. · 169 Vanlint D. · 114 Vast N. · 47, 245 Vaughan G. · 144 Vavrova H. · 71, 74, 76 Vekilova O.Y. · 48 Velazquez-Estrada R.M. · 92 Verret C. · 82, 89 Ves S. · 219 Veysman M.E. · 60 Vilanova M. · 103 Vogel R.F. · 35 Volkova Ya.Yu. · 212, 222 Volodina V.A. · 215 Voronovskii A.N. · 314 Vorontsov G.V. · 261 Vrel D. · 365
W
Wågberg T. · 226 Wagner F. · 170 Wang W. · 128, 159 Wang X. · 230, 251, 274 Waplak S. · 202, 203 Weck G. · 201 Weckert E. · 141 Weinberg N. · 179, 334, 340 Weinberger B. · 133 Weinstein B.A. · 240 Wenk H.R. · 160 Wensley J.R. · 303 Wieja K. · 86, 88 Wierzbicki M. · 83, 85, 86 Wilhelm H. · 270 Wilson C. · 199
Winkler B. · 141 Winter R. · 104 Wiśniewska K. · 78, 79, 81 Wolny J. · 178 Woodhead K. · 341, 366 Woodland A.B. · 177 Wortmann G. · 125, 308
X
Xie Y. · 281 Xu W.M. · 280, 284
Y
Yagafarov O.F. · 193 Yagi T. · 147 Yakushev V.V. · 351 Yamada I. · 343 Yang L. · 191 Yang W. · 180 Yao M. · 226 Yoshimura Y. · 108, 194, 195 Yunovich A.E. · 258
Z
Zaitsev-Zotov S.V. · 314 Zalibekov U.Z. · 252, 254, 255 Zamora, A. · 72 Zarechnaya E.Yu. · 41, 232 Zaynulin Y.G. · 354 Zdanowska-Frączek M. · 306 Zeckler D. · 82 Zentková M. · 287, 292 Zerr A. · 137 Zhang P. · 240 Zhukov A.N. · 215, 351 Zhulanov V.V. · 218 Zinin P. · 120 Zitny R. · 75 Zubov E. · 312
377
Preconference School
The EHPRG conferences are highly multidisciplinary, in line with the rapid growth of high pressure activities in Chemistry, Physics, Material Science, Geophysics, Bioscience, Biotechnology and Food Science.
This year, we propose to combine the conference with a school held in the three days preceding the main international meeting. Such a school will act to highlight the different topics of the conference. It will allow students and newcomers in the field of high pressure to become familiar with some of the basic ideas of multidisciplinary topics in an academic environment, and therefore increase the effectiveness of their participation and exchange of scientific ideas.
It will also be the occasion to establish an interdisciplinary forum where young European scientists can exchange ideas.
Overview
A series of thematic and overview lectures will be given by leading scientists in each field (Chemistry, Physics, Material Science, Geophysics, Bioscience). This will provide the attendees with a good level of background knowledge and so increase the efficiency of their participation in the main EHPRG conference. For many young researchers it will also be a unique opportunity to review recent, ongoing and future activities; to discover new hot topics, or simply to deepen their knowledge in some areas.
Location
Campus Boucicaut, 140 rue de Lourmel, 75015 Paris Bus stops “Boucicaut” N° 42 or 62 Subway stops “Boucicaut” N°8 “Charles-Michel” N°10 Alternatively “Javel” RER C
Dates September 4th to 6th
Registration Fees
This pre-conference school is free of charge, however the number of students is limited.
378
Schedule
Frid
ay
Sa
turd
ay
Su
nd
ay
Se
pte
mb
er 4
Se
pte
mb
er 5
Se
pte
mb
er 6
S. Klo
tzK
. Syassen
High pressure neutron scattering:
an introduction
Simple m
etals under pressure:
Ashcroft-M
ermin and beyond
J.P. Itié
G. R
ozen
berg
Synchrotron radiation techniques
for high pressure experiments
Magnetic/electronic phenom
ena
and related structural transitions
in TM com
pounds under high pressure
11
:00
-11
:30
Co
ffee
Bre
ak
Co
ffee
Bre
ak
F. Datch
iP
. McM
illan
Vibrational spectroscopies at H
P
(Ram
an, Brillouin, IR
)
Solid state chemistry at high pressure
12
:30
-14
:30
Lun
ch
A. M
. SaittaJ. K
reisel
Tutorial on atomistic calculations
(classical and ab initio)
The effect of high-pressure on
dielectric AB
O3 perovskite-type oxides
P. R
aterron
C. Lo
up
iac
Earth's Mantle R
heology:
Insights from H
igh-Pressure Experiments
Food ingredients under high pressure:
an overview
16
:30
-17
:00
Co
ffee
Bre
ak
Co
ffee
Bre
ak
G. Fiq
uet
R. Lan
ge
Structure, Elastic properties of Iron
and Alloys at Earth's Core Conditions:
From Static to Shock Experim
ents
Why applying high pressure for
studying biological processes that are
occurring at atmospheric pressure?
9:00-10:00
10:00-11:00
15:30-16:30
17:00-18:00
11:30-12:30
14:30-15:30
379
Sponsors & Exhibitors
Agir Technologies BP 11, 21220 Gevrey-Chambertin, France Tél:(33) (0)3 80 51 81 31 Fax: (33) (0)3 80 51 81 36 E-mail: [email protected] URL: www.agir-technologies.com
ALMAX Industries
Wagenmakerijstraat 5,
B-8600 Diksmuide, Belgium
Tel: +32 51 55 56 37
Direct tel: +32 475 69 44 30
Fax: +32 51 55 56 38
E-mail: [email protected]
URL: www.almax-industries.com
BETSA France
ZI 2 bis, Rue Ambroise Croizat,
F 77370 NANGIS France
Tél : (+33) 1 64 08 27 33
Fax : (+33) 1 64 08 33 51
E-mail : [email protected]
URL: www.betsa.fr
D'ANVILS Ltd
P.O. Box 1200,
Hod-Hasharon 45111, ISRAEL.
FAX:+972-9-7669133
E-mail: [email protected]
380
easyLab Technologies Ltd
The University of Reading Earley Gate, Whiteknights Road Reading, Berkshire, RG6 6BZ, U.K. Tel: +44 (0)118 935 7272 Fax: +44 (0)118 935 7271 E-mail: [email protected] URL: www.easylab.co.uk
MG 63 9, Route de Frugères 43360 Vergongheon, France Tel: +33 4 71 76 93 51 Fax:+33 4 71 76 00 78 E-Mail: [email protected] URL : http://www.mg63.com
NOVA SWISS 31, rue Denis Papin F-77240 CESSON Tel. +33 (0) 1 64 41 18 48 Fax. +33 (0) 1 60 63 80 92 E-Mail: [email protected] URL :http://www.novaswiss.ch
Sanchez Technologie ZA de l'Orme - BP37 95270 Viarmes, France Tel: +33 1 30 35 40 42 Fax:+33 1 30 35 33 92 E-mail: [email protected]
URL: www.stfrance.com
SITEC-Sieber Engineering AG
Aschbach 621
CH-8124 Maur / Zurich Switzerland
Tel: +41 (0)44 982 2070 Fax: +41 (0)44 982 2079
E-mail: [email protected]
URL: www.sitec-hp.ch
381
Synchrotron SOLEIL
L'Orme des Merisiers, Saint-Aubin - BP 48
91192 GIF-sur-YVETTE CEDEX
Tél. 01 69 35 90 00
URL: www.synchrotron-soleil.fr
Groupe TOTAL
2, place Jean Millier, La Défense 6
92400 Courbevoie, France.
Tél. : +33 (0) 1 47 44 45 46
URL: www.total.com
High Pressure Research
ISSN: 1477-2299 (electronic)
ISSN: 0895-7959 (paper)
Taylor & Francis
Informaworld
URL: http://www.informaworld.com
382
![Welcome [tc18.tableau.com] · + mapbox 0 00 ableau 'conference" ableau 'conference" ableau 'conference" tableau conference . o poli tableau conference . ableau 'conference" tableau](https://img.pdfslide.us/doc/110x75/603c384c36ee9629d81b13a8/welcome-tc18-mapbox-0-00-ableau-conference-ableau-conference.jpg)
