HR: 1340h
AN: MR23C-1515    [Abstracts]
TI: Quantum Monte Carlo Study of the Elastic Instability of Stishovite Under Pressure
AU: * Driver, K P
EM: driver@mps.ohio-state.edu
AF: The Ohio State University, 1040 Physics Research Building 191 West Woodruff Avenue, Columbus, OH 43210, United States
AU: Cohen, R E
EM: cohen@gl.ciw.edu
AF: Carnegie Institution of Washington, Geophysical Laboratory 5251 Broad Branch Rd., Washington, DC 20015, United States
AU: Rios, P L
EM: pl275@cam.ac.uk
AF: University of Cambridge, Theory of Condensed Matter Group Cavendish Laboratory J. J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
AU: Towler, M
EM: mdt26@cam.ac.uk
AF: University of Cambridge, Theory of Condensed Matter Group Cavendish Laboratory J. J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
AU: Needs, R
EM: rn11@cam.ac.uk
AF: University of Cambridge, Theory of Condensed Matter Group Cavendish Laboratory J. J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
AU: Wilkins, J W
EM: wilkins@mps.ohio-state.edu
AF: The Ohio State University, 1040 Physics Research Building 191 West Woodruff Avenue, Columbus, OH 43210, United States
AB: Stishovite is a octahedrally coordinated polymorph of silica which becomes stable at pressures consistent with Earth's lower mantle (10 GPa). The elastic properties of stishovite are potentially important for explaining seismic structure and it serves as a model system for other six-coordinated silicates. At a pressure near 50 GPa, stishovite transforms to the CaCl₂-type structure due to an instability in the elastic shear modulus, c₁₁-c₁₂. The instability was predicted by density functional theory (DFT) calculations and later confirmed by Raman spectroscopy and x-ray diffraction. This well understood instability is used to benchmark the ability of Quantum Monte Carlo (QMC) to predict elastic constants. QMC calculates the softening of the elastic shear modulus over the pressure range of 0 to 50 GPa. Results show the QMC elastic shear modulus softens from 270 to 0 GPa in agreement with previous DFT and experimental results. Although at factor of 1400 more in computational cost over DFT, QMC is capable of predicting elastic properties of minerals under pressure accurately. Computations were performed at NERSC on the Cray-XT4 within the early user program. Financial support is provided by the NSF (EAR-0530282, EAR-0310139) and the DOE (DE-FG02-99ER45795).
DE: 0500 COMPUTATIONAL GEOPHYSICS (3200, 3252, 7833)
DE: 3909 Elasticity and anelasticity
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting