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Prediction of Phase Transition in CaSiO$_3$ Perovskite and Implications for Lower Mantle Structure

Lars Stixrude·Ronald E. Cohen·Rici Yu·Henry Krakauer
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Abstract

First principles linear response calculations are used to investigate the lattice dynamics of what is thought to be the third most abundant phase in the lower mantle, CaSiO_3 perovskite. The commonly assumed cubic structure (Pm3m) is found to be dynamically unstable at all pressures, exhibiting unstable modes along the Brillouin zone edge from the M-point to the R-point. Based on these results, we predict that the ground state structure of CaSiO_3 perovskite is a distorted phase with lower than cubic symmetry. We predict that a phase transition occurs in CaSiO_3 perovskite within the earth's lower mantle from the low temperature distorted phase to the cubic phase at high temperature. The predicted phase transition provides a possible explanation of some of the seismological observations of reflective features within the lower mantle.

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BibTeXRIS

Lars Stixrude, Ronald E. Cohen, Rici Yu, Henry Krakauer. 1996-10-31. Prediction of Phase Transition in CaSiO$_3$ Perovskite and Implications for Lower Mantle Structure. https://arxiv.org/abs/physics/9610023

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