High Pressure Spectroscopic Opportunities (mostly infrared and mostly Earth Sciences) and NSLS-II

1. High Pressure Spectroscopic Opportunities (mostly infrared and mostly Earth Sciences) and NSLS-II Talk Organization: • A Brief COMPRES Description/Commercial • Routine (but important!) Infrared Spectroscopy at High Pressure 3) More Demanding Synchrotron-based Infrared Spectroscopic Applications Today: Focus on infrared--highly complementary techniques include inelastic phonon scattering, X-ray Raman, etc.

2. Consortium for Materials Properties Research in EarthSciences Funded by NSF Division of Earth Sciences [2002-2012] Goals: Facilitate the operation and accessibility of high-pressure beamlines. support development of new high-P technologies, and advocate for high-P related science and education programs to funding agencies. President: Bob Liebermann, SBU Executive Committee; Quentin Williams, UC Santa Cruz, Chair Mike Brown, U. Washington, Vice Chair Carl Agee, U. New Mexico Jay Bass, U. Illinois Urbana-Champaign Don Weidner, SBU Mark Rivers, APS/Chicago, Chair Facilities Committee Nancy Ross, Virginia Tech, Chair Infrastructure Committee NSLS-II Meeting July 17-18, 2007

3. Budget for COMPRES Past Coop Agreement 2006-07: $2100K Five Year [2002-07]: $10,800K Present budget: 2007-08: $2100K 2007-2012: $11,500K In 07-08, roughly half of budget allocated for technical support, equipment at NSLS--X17B, C (Multi-anvil, Diamond Cell X-rays) and U2A (Infrared of DAC and geologic samples)

4. COMPRES Who is represented: 50 US Member Institutions conducting high-pressure Earth Sciences research. Communities not represented: Microfocus infrared and x-ray geosciences users examples: Stardust Comet 81P/Wild 2 samples, lots of micromineralogy of terrestrial and meteoritic samples… High Pressure Physics, Chemistry and Materials Science

5. Advantages of Synchrotron IR for High Pressure Applications • Microfocus capabilities Key for laser-heated spots, Trace constituents (water, etc.) • Far-infrared intensity Critical for lattice dynamics; but hard w/conventional sources 3) Rapid measurements--high P kinetics 4) Reflectance from high pressure samples Produces constraints on ionic polarizability and optical constants, band structure

6. A Few High Pressure Earth Sciences Issues addressed by IR spectroscopy 1) Thermodynamics at extreme conditions--for example, controls temperature distribution within the planet • Water and carbon storage mechanisms in the Earth • Structure of magmas/melts/glasses • Phase transitions and bonding properties of deep Earth constituents. • Thermal and radiative conductivity of deep Earth constituents.

7. Synchrotron Source Advantage Advantages: Signal to Noise, thus spatial selectivity, smaller and/or more opaque samples, intensity in far-IR and for reflectivity From: M. Martin, ALS

8. NSLS-II Mid-IR Brightness Lattice, Functional Group Vibs. H-related Vibs.

9. NSLS-II Very Far-IR Brightness • Large gap dipole magnets enhance far-IR intensity Lattice, Functional Group Vibs.

10. Infrared Anvil Transparency • Early recognition of spectral limitations of diamonds, as well as sapphire and BN as anvils; SiC is a later addition. SiC (moissonite) at High Pressures: Liu, Xu, Scott, Williams, Mao, Hemley, RSI, 2004 Lippincott et al., Anal. Chem., 1961

11. FTIR: Basically, Pretty Simple Optics and, an ideal combination with a synchrotron No requirement that the light be IR! Resolution a 1/2pxmax; j-stop can also affect resolution. BNL After Perkin-Elmer

12. Bond Strength and Symmetry Diatomic Hooke’s Law IR activity hinges on change in dipole moment ~3650 cm-1 ~1600 cm-1 ~3750 cm-1 From J. Mirick, GMU, www.bluelaze.com

13. Comparatively Routine (but valuable) High Pressure Infrared Measurements • Pressure shifts of vibrational modes; increases in force constants, changes in anharmonicity, and shifts in bonding. • Characterizations of phase transitions or shifts in coordination. • Pressure-induced band gap closure

14. Relatively Common High-P Infrared Measurements • Pressure-induced mode shifts (Bond strength) • Phase transition-induced mode shifts (Symmetry changes) Each are fundamental for monitoring pressure-induced changes in bonding properties, and have macroscopic thermodynamic implications, as well… b-Mg2SiO4-a high pressure phase

15. Temperature Distribution in Earth • Smooth regions are modulated by the phonon spectrum Williams, CMB Monograph, 1998

16. The Adiabat • In most of Earth’s Interior, thermal buoyancy dominates over viscous effects • Interior is convecting, and near adiabatic (dT/dr)ad = gT/r; or ln(T/To) = g ln(r/ro) Thermodynamically, g is V(dP/dE)s, or Thermal Expansion/(Compressibility*r*Heat Capacity) --> A Measure of Anharmonicity

17. g, the Grüneisen Parameter and the Geotherm • can also be shown to equal • S(dwi/w)/(dV/V), • Where the sum is over the i modes of the crystal. • So, our understanding of the temperature distribution in the convective portion of the planet(s) hinges on knowing the vibrational spectrum and its volume dependence: thus, lots and lots of determinations of pressure- (and temperature-) induced mode shifts…

18. A Subtle Transition in CaCO3-Calcite From the left: CO3 asymmetric stretches, symmetric stretches, and out-of-plane bend Catalli and Williams, Am. Min, 2005.

19. Calcite-III IR and X-ray Complex, unquenchable structures at high pressure may produce difficult-to-interpret x-ray patterns; diagnostic changes may be observed in vibrations of molecular-like units. This phase transition may be between two monoclinic phases. Catalli & Williams, Am. Min., 2005 Fiquet et al., Am. Min., 1994

20. Quartz and Silica Glass: A mildly more Exotic Structural Transformation • And, give or take, most tetrahedral silicates compressed at 300 K seem to look about the same at 30-40+ GPa: the rationale for this remains unclear…

21. Band Gap Closure Cervantes et al., J.P.C.S., 2002 A different style of IR measurement

22. Probably Understudied Phenomena at high P • Overtones, Combinations • Reflectance, TO/LO splitting • Band Gap Closure, Electronic Structure • High T phases, liquids • Visible Spectroscopy • Far-IR spectroscopy

23. Advantages of Synchrotron IR for High Pressure Applications • Microfocus capabilities Key for laser-heated spots, Trace constituents (water, etc.) • Far-infrared intensity Critical for lattice dynamics; but hard w/conventional sources • Reflectance from high pressure samples Produces constraints on ionic polarizability, band structure

24. S. Jacobsen

25. A Far-IR example--Muscovite Mica Al-Si Layer K+ displacement K-ions KAl3Si3O10(OH)2 in a layered structure Williams, Knittle, Scott, Liu et al.,in prep.

26. Hydroxyl Stretch of Muscovite A probe of another portion of the structure Williams, Knittle, Scott, Liu et al.,in prep.

27. Absorption vs. Reflectance LO TO From: minerals.gps.caltech.edu TO-LO (Transverse Optic-Longitudinal Optic) Splitting--Associated with strongly polarized vibrations/structures. LO appears in reflectance geometry.

28. Reflectance of Ice at High Pressures Documentation of Symmetrization of the O-H-O Distance--using reflectance to invert for optical constants of water. Struzhkin, Goncharov, Hemley, Mao, PRL, 1997

29. Cascading Resonances in H2O Struzhkin, Goncharov, Hemley, Mao, PRL, 1997

30. Protons at High Pressure in Hydrogen-bonded Systems O------H…………………………O

31. Overtones in Ice • Splittings, decrease in strength and ultimate disappearance of each overtone… Larsen and Williams, PRB, 1998

32. Potential Surface of H2O Two Born-Mayer plus a Buckingham potential; Pressure-induced Increase in polarizability of oxygen required. Larsen and Williams

33. Infrared of Melts at High P/T • Hampered by large absorption • Reflectance studies may ultimately prove most useful • Overtones are useful for strongly bound species • Thermal emission can be problematic O-H Stretch + O-H Libration O-H Stretch + H-O-H Bend Sowerby and Keppler, Am. Min., 1999

34. Conclusions • Vibrational spectroscopy remains the most prevalent means by which amorphous materials, or materials difficult to characterize by structural techniques, are characterized at high pressures; from an Earth Sciences perspective, such studies remain in their infancy. • There has only been limited advantage taken of the unique aspects of synchrotron-infrared studies: high spatial resolution, far-infrared strength, and high pressure reflectance studies (and, high P time-resolved IR studies are really limited…). • The future of high-P synchrotron infrared spectroscopy is bright, and NSLS is well poised in this arena…

36. Barrier Height from Overtone Disappearance Larsen and Williams

37. Probing High-P Melts Quenched in T • Should ‘lock in’ structure at the temperature of a fast glass transition • Spatial selectivity could be critical in probing material exposed to different temperatures IR Spectrum: (Mg0.9,Fe0.1)SiO3 + 3 wt% H2O, Melted at 38.7 GPa and decompressed Closmann and Williams, Am. Min.

38. Barrier Decrease -> Overtone Annihilation