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First Principles Investigations of Plutonium Americium and their Mixtures using
Dynamical Mean Field Theory
Washington February 5-8 (2007).
Gabriel .Kotliar Physics Department and Center for Materials Theory Rutgers University.
Funded by : DOE BES and NNSA .
Outline and Conclusion
• First Principles Computations of Actinides. • DMFT Results for Plutonium and Americium• Preliminary Results for compounds PuO2, Pu.5 Am.5.
•Mott transition in the actinide series: important science problem.•New theoretical methodologies developed at Universities. DMFT concepts, allow close interaction with experimentalists, key validation and progress.
Computational Approach to a First Principles Description of the
Actinides must include• Relativistic Effects, Spin Orbit Coupling• Realistic band structure, complex
structures• Atomic Multiplet effects (F0 F2 F4 F6)
• Treat localization –delocalization on the same footing.
• LDA+DMFT. Compute total energies from a functional of the photoemission spectra.
DMFT Phonons in fcc DMFT Phonons in fcc -Pu-Pu
C11 (GPa) C44 (GPa) C12 (GPa) C'(GPa)
Theory 34.56 33.03 26.81 3.88
Experiment 36.28 33.59 26.73 4.78
( Dai, Savrasov, Kotliar,Ledbetter, Migliori, Abrahams, Science, 9 May 2003)
(experiments from Wong et.al, Science, 22 August 2003)
Volume and Spectra alpa->delta volume collapse transition
F0=4,F2=6.1
F0=4.5,F2=7.15
Gouder Havela Lander
Americium
"soft" phase
f localized
"hard" phase
f bonding
Mott Transition?
f6 -> L=3, S=3, J=0
A.Lindbaum, S. Heathman, K. Litfin, and Y. Méresse, Phys. Rev. B 63, 214101 (2001)
J.-C. Griveau, J. Rebizant, G. H. Lander, and G.KotliarPhys. Rev. Lett. 94, 097002 (2005)
Am within LDA+DMFT
S. Y. Savrasov, K. Haule, and G. KotliarPhys. Rev. Lett. 96, 036404 (2006)
F(0)=4.5 eV F(2)=8.0 eVF(4)=5.4 eV F(6)=4.0 eV
Large multiple effects:
core
vale
nce
4d3/2
4d5/2
5f5/2
5f7/2
Exci
tati
ons
from
4d c
ore
to 5
f vale
nce
Electron energy loss spectroscopy (EELS) orX-ray absorption spectroscopy (XAS)
Energy loss [eV]
Core splitting~50eV
4d5/2->5f7/2
4d3/2->5f5/2
hv
Core
split
ting~
50
eV
Probe for Valence and Multiplet structure: EELS&XAS
A plot of the X-ray absorption as a function of energy
Branching ratio B=A5/2/(A5/2+A3/2)B=B0 - 4/15<l.s>/(14-nf)
From J. Shim K. Haule and G. Kotliar to appear in Nature.
B=B0 - 4/15<l.s>/(14-nf) B0 = (3/5) (for d->f transitions)
One measured quantity B, two unknownsClose to atom (IC regime)
Itinerancy tends to decrease <l.s>
B=B0 - 4/15<l.s>/(14-nf)
[a] G. Van der Laan et al., PRL 93, 97401 (2004).[b] G. Kalkowski et al., PRB 35, 2667 (1987)[c] K.T. Moore et al., PRB 73, 33109 (2006).
LD
A+
DM
FT
First results on Compounds, PuO2, Pu-Am mixture, 50%Pu,50%Am
Lattice expands -> Kondo collapse is expected
charge transferPu phase stabilized by shift tomixed valence nf~5.2->nf~5.4
Hybridization decreases, but nf increases,
Tk does not change significantly!
Outline and Conclusion
• First Principles Computations of Actinides. • DMFT Results for Plutonium and Americium• Preliminary Results for compounds PuO2, Pu.5 Am.5.
•Mott transition in the actinide series: important science problem.•New theoretical methodologies developed at Universities. DMFT concepts, allow close interaction with experimentalists, key validation and progress.
Acknowlegment References-Collaborators
• Electronic correlations in metallic Plutonium within dynamical mean-field picture: S. Savrasov, G. Kotliar, and E. Abrahams, Nature 410, 793 (2001).
• Calculated Phonon Spectra of Plutonium at High Temperatures: X. Dai, S. Y. Savrasov, G. Kotliar, A. Migliori, H. Ledbetter, and E. Abrahams, Science 300, 953-955 (2003).
• Many-Body Electronic Structure of Americium metal: Sergej Y. Savrasov, Kristjan Haule, Gabriel Kotliar, Phys. Rev. Lett. 96, 036404 (2006).
• J. Shim K. Haule and G. Kotliar , Fluctuating valence in a correlated solid and the anomalous properties of delta-plutonium: to appear in Nature next month.
Experimentalists: LANL: A. Migliori, (resonant ultrasound) J. Singleton (magnetotrasnport ) J. Thompson, (EELS X-Ray J. Joyce (Photoemission), J. Lashley (specific heat) Livermore: J. Wong (X Ray scattering) K. Moore J. Tobin (EELS and XAS ) M. Fluss (transport) ITU: . L. Havela J. C. Griveaux and G. Lander (transport under pressure )