Anders Nilsson , Stanford Synchrotron Radiation Lightsource Stockholm University
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Transcript of 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
Tokushima et al., Chem. Phys. Lett. 460 (2008) 387
X-ray Emission SpectroscopyGas
Ice
A very homogeneouswater model
Outer
Inner
hv
Increasing hydrogen bonding
Energy
Tokushima et al., Chem. Phys. Lett. 460 (2008) 387
X-ray SpectroscopyGas
Ice
WATERTwo Peaks !!!
Two different components
Outer
Inner
hv
Increasing hydrogen bonding
Energy
Tokushima et al., Chem. Phys. Lett. 460 (2008) 387
X-ray SpectroscopyGas
Ice
Outer
Inner
hv
Increasing hydrogen bonding
Energy
Tokushima et al., Chem. Phys. Lett. 460 (2008) 387
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
Tokushima et al., Chem. Phys. Lett. 460 (2008) 387
• 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
Ssssssssssssssssssssssss25 50 75 1000-25-50
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
Ssssssssssssssssssssssss25 50 75 1000-25-50
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