Anders Nilsson , Stanford Synchrotron Radiation Lightsource Stockholm University

Anders Nilsson, Stanford Synchrotron Radiation LightsourceStockholm University

X-rays Shines Light on the Water Mystery

Coworkers, Funding and ExperimentsPhilippe Wernet/SSRL (BESSY)

Congcong Huang/SSRL

Uwe Bergmann/LCLS

Hirohito Ogasawara/SSRL

Dennis Nordlund/SSRL

Lars Åke Näslund/SSRL

Sarp Kaya/SSRL

Ira Waluyo/SSRL-SU Chemistry

Tomas Weiss/SSRL

Ningdong Huang/SSRL-SU Applied Physics

Trevor Mcqueen/SSRL-SU Chemistry

Chen Chen/SSRL-SU Chemistry

Jonas Sellberg/SSRL-Stockholm University

Mike Bogan/PULSE

Dmitri Starodub/PULSE

Raymond Sierra/PULSE

Experiments: SSRL (4.0, 6.2, 5.1, 4-2) APS (BioCat beamline), ALS beamline (8.0, 11.0), Spring 8 and MAXlab (511)

Lars Pettersson/Stockholm

Matteo Cavalleri/Stockholm

Michael Odelius/Stockholm

Michael. Leetma/Stockholm

Mathias. Ljungberg/Stockholm

Thor Wikfeldt/Stockholm

Lars Ojamäe/Linköping

Takashi Tokushima/Spring8

Yoshihisa Harada/Spring8

Yuka Horikawa/Spring 8

Shik Shin/Tokyo

National Science Foundation (NSF)Department of Energy (DOE)

Swedish Research Council (VR)Swedish Foundation for Strategic Research (SFF)

The Blue Planet

Climate Change Water Issues

Access to Clean WaterThe Challenge for the World with Climate Change

Gore, Inconvenient Truth

Water denser than ice

Density of the liquid higher than the solid

Normal liquid (ethanol, gasoline,etc)Solid more dense than liquid

Density Maximum

At the bottom of the glass is 4 °C water

Ssssssssssssssssssssssss25 50 75 1000-25-50

Temperature/ °C

dddddddddddd

density

Normal liquid

Water

High Heat Capacity

Ocean current stabilizes the climate

The amount of heat to add for the temperature to rise 1°C

It stabilizes the temperature in the Oceans

High Surface Tension

Water has extremely high surface tension

Water droplets can formSpiders can walk on water

Anomalous Properties of Water

. [P. G. Debenedetti, J. Phys.: Condens. Matter 15, R1669 (2003)]

<(V)2>=VkBTT

<(S)2>=NkBcp

<(S V)>=VkBT

Density

Isothermal Compressibility

Thermal expansion

Heat Capacity

High boiling point

Periodic table

Temperature °C

Molecular mass

50 100 150 200 250

100

50

-50

-100

-150

-200

0

0

RoomTemp

H2O

SnH4

GeH4

SiH4

CH4

H2S

H2Po

H2Te

H2Se

Water should be a gas at room temperatureWhy not?

Boiling points

O-H chemical bonds

Lone pairs

electrostatic interaction

Positive H atomsNegative O atoms

2 Å1 Å

The Hydrogen Bond

ssssssssssssssssssssssssssssssss

Ssssssssssssssssssssssssssssssss

Ssssssssssssssss

Dddddddddd

Tetrahedral Coordination

Oxygen

Hydrogen

Ice

Open spaces where no molecules are present

If molecules move to fill the open space there will be an increase in the density

What is WaterWhat is Water?

electron

nucleusorbit

X-ray Absorption

Inner

Outer

electron

nucleusorbit

X-ray Emission

Inner

Outer

X-ray Emission spectroscopy

XES

h

1b2 1b13a1

Gas

Liquid

1b2

3a1

1b1

4a1

1b2

2a1

O1s

Tokushima et al., Chem. Phys. Lett. 460 (2008) 387

X-ray Emission Spectroscopy

Gas

Ice

Outer

Inner

hv

Energy

Increasing hydrogen bonding


X-ray Emission SpectroscopyGas

Ice

A very homogeneouswater model

Outer

Inner

hv


Energy


X-ray SpectroscopyGas

Ice

WATERTwo Peaks !!!

Two different components

Outer

Inner

hv


Energy


X-ray SpectroscopyGas

Ice

Outer

Inner

hv


Energy


Temperature Dependence

Tokushima et al., Chem. Phys. Lett. 460 (2008) 387Huang et al., PNAS. 106 (2009) 15214

• Intensity transferred tetrahedral to disordered as temperature is increased (fewer H-bonds)

• NO broadening, NO new peaks: Either tetrahedral OR very disordered

Temperature Changes of Distorted Component

FixedShifts towards gas phase with increasing temperature

Huang et al., PNAS. 106 (2009) 15214

• Distorted species changes with temperature

• Tetrahedral fixed

Summary X-ray Emission Spectroscopy


• Tetrahedral loses intensity with temperature, but peak at fixed energy

• Distorted gains intensity and disperses with temperature

• Energy taken up through: - Thermal excitation of distorted species - Breaking up a fraction of tetrahedral

species

Huang et al., PNAS. 106 (2009) 15214

20-30 %

70-80 %

localized bonds

delocalized bonds

Bonds vs. Entropy

Bond Energy

Entropy

Two Types – Inhomogeneous?Small-Angle X-ray Scattering (SAXS)

k

incident

scatteredk’

Qk

incident

scatteredk’ k

incident

scatteredk’

Q

d d

Small angles “trick” the lightthat distances are short

Projection…λ

λ

d ~ 2π/Q

Measures density contrastSize of macromolecules,

colloids etc (Guinier analysis)Critical density fluctuations

(Ornstein-Zernike)

Theoretical curve for single component

Very HomogeneousSPC/E

Surprising experimental result

Enhancement showing heterogeneitysmall regions

Hypothetical WaterHomogeneous

Experimental Water

Minimum related to size

Huang et al., PNAS. 106 (2009) 15214

SAXS – Ambient to Supercooled Regime

Very good fit to previous dataTBTnkS )0(

The isothermal compressibility T

Huang et al., PNAS 106, 15214 (2009); PNAS 107, E45 (2010); JCP 133, 134504 (2010)

At low Q rangeS(Q) shows an

unusual enhancement

22

1

QQS A

gA(r)~exp(-r/ζ)/r (r>>1)

Q<<1)

F.T.

Much largerenhancements(fluctuations!)

at lower T

Snapshot from MD at 253KGrey: High tetrahedrality

Red: High density

Note: XES seesvery little intermediate

speciesWikfeldt et al., unpublished

Dance Restaurant

People at the table are more socially bonded, local order, low densityPeople dancing are disordered but excited and moves around, higher density

Exchange between dancing and sitting people

Cooling

lowering temperature

Bond Energy in Tetrahedral becomes more important

Converting some Disordered structures to ice-like structures

Phase Diagram of Water and Ice

t

C1

C2LDA

HDAWidom Line

(HDA)=1.17 g/cm3

(VHDA)=1.25

(LDA)=0.94

(Ih)=0.92

(Ic)=0.92

(C1)=0.322

15 Ice Polymorphs

2 Amorphous Ices

LDA & HDA,VHDA

Widom Line and 2nd Critical Point

The Widom line is anextension of the

coexistence line beyondthe critical point.

Thermodynamical properties have maximabut do not diverge along

this line

Apparent Power Law – Widom Line

.32

.52

Poole et al., Nature 360, 324 (1992)

Fit ζ to (apparent) powerlawwith 0

1/ sTT

Critical phenomena characterized by power laws with critical exponents

2nd critical point scenarioFluctuations between

HDL/LDLPoole et al., Nature 360, 324 (1992)

Huang et al. JCP 133, 134504 (2010)

Water denser than the solid

Open space inside the rings

Ice, lower densityMore open space

Water, higher densityDisordered structure allows more dense

packing

Density Maximum

Tetrahedral lower densityDisordered higher density


Temperature/ °C

dddddddddddd

density

4 °C

Density Maximum

Tetrahedral lower density Disordered higher density

With decreasing temperature we increase the number of tetrahedral structures which have

lower density


Temperature/ °C

dddddddddddd

density

High Heat Capacity

It stabilizes the temperature in the Oceans

Much of the extra heat is used to convert the tetrahedral structures to the disordered without increasing the kinetic energy of the particles

High Surface Tension

Temperature °C

Molecular mass

50 100 150 200 250

100

50

-50

-100

-150

-200

0

0

H2O

SnH4

GeH4

SiH4

CH4

H2S

H2Po

H2Te

H2Se

Hydrogen bonds in water makes the glue Molecular mass makes gasoline a liquid butweak bonding in between the molecules

Boiling points

The important aspects in my lecture

Two local structures

Ice-like low density (low energy, low entropy)

Disordered high density (high energy, high entropy)

Fluctuations on a 1nm length scaleIncreases with decreasing

temperature

Water is maybe not so strange but special

Documents

Anders Nilsson , Stanford Synchrotron Radiation Lightsource Stockholm University