Equation of state and and phase transitions of (Mg,Fe)SiO3 perovskite and post-perovskites from quantum Monte Carlo and Density Functional Theory

Ronald E Cohen, UCL, Dept. of Physics, London, United Kingdom; Carnegie Institution for Science, Earth and Planets Laboratory, Washington, United States, Yangzheng Lin, Carnegie Institution for Science, Geophysical Laboratory, Washington, DC, United States, Kevin P Driver, University of California Berkeley, Berkeley, CA, United States and Burkhard Militzer, University of California Berkeley, Department of Astronomy, Berkeley, United States

Contact First Author: Ronald E Cohen; rcohen@carnegiescience.edu

Previously Published Material: 50% in Y. Lin, R. E. Cohen, S. Stackhouse, K. P. Driver, B. Militzer, L. Shulenburger, and J. Kim, Phys. Rev. B 90 (2014).; R. E. Cohen and Y. Lin, Phys. Rev. B 90 (2014).

Abstract ID#: 33546

 

English Abstract:
We have performed quantum Monte Carlo (QMC) simulations and density functional theory calculations

to study the equations of state and phase transition of MgSiO3 perovskite (Pv, bridgmanite) and post-perovskite (PPv) .[1] The ground-state energies were derived using quantum QMC simulations and the temperature-dependent Helmholtz free energies were calculated within the quasiharmonic approximation and density functional perturbation theory. Agreement with experiments is improved over DFT alone. Furthermore, we obtain statistical error bounds on the results, rather than the unconstrained errors of DFT. The Pv-PPv phase boundary calculated from our QMC equations of state is also consistent with experiments, and better than previous local density approximation calculations. In order to understand the H-phase reported in (Mg,Fe)SiO3 [2], we have performed evolutionary structure searching for FeSiO3.[3] We find a new structure type which may be consistent with the experimental observations. We are now performing QMC and DFT studies of FeSiO3 and (Mg,Fe)SiO3 perovskite and post-perovskites. This work is supported by NSF and the ERC Advanced Grant ToMCaT.

[1] Y. Lin, R. E. Cohen, S. Stackhouse, K. P. Driver, B. Militzer, L. Shulenburger, and J. Kim, Phys. Rev. B 90 (2014).
[2] L. Zhang et al., Science 344, 877 (2014).
[3] R. E. Cohen and Y. Lin, Phys. Rev. B 90 (2014).

Back to: Perovskites Into the Next Millennium