Elastic Properties of CaSiO3 Perovskite from ab initio Molecular Dynamics

Shigeaki Ono

doi:10.3390/e15104300

Abstract

Ab initio molecular dynamics simulations were performed to investigate the elasticity of cubic CaSiO3 perovskite at high pressure and temperature. All three independent elastic constants for cubic CaSiO3 perovskite, C11, C12, and C44, were calculated from the computation of stress generated by small strains. The elastic constants were used to estimate the moduli and seismic wave velocities at the high pressure and high temperature characteristic of the Earth’s interior. The dependence of temperature for sound wave velocities decreased as the pressure increased. There was little difference between the estimated compressional sound wave velocity (VP) in cubic CaSiO3 perovskite and that in the Earth’s mantle, determined by seismological data. By contrast, a significant difference between the estimated shear sound wave velocity (VS) and that in the Earth’s mantle was confirmed. The elastic properties of cubic CaSiO3 perovskite cannot explain the properties of the Earth’s lower mantle, indicating that the cubic CaSiO3 perovskite phase is a minor mineral in the Earth’s lower mantle.

Highlights

Mineral physics constraints on the composition of the Earth’s lower mantle rely on knowledge of the equations of state (EOSs) and sound wave velocities in candidate minerals
The EOS of cubic CaSiO3 perovskite has been investigated in a previous experimental study [20]
Recent theoretical studies have investigated the physical properties of materials under high pressure and high temperature using first-principles calculations

Summary

Introduction

Mineral physics constraints on the composition of the Earth’s lower mantle rely on knowledge of the equations of state (EOSs) and sound wave velocities in candidate minerals. According to reliable estimates of the composition of the Earth, an MgO-FeO-SiO2-CaO-Al2O3 system could comprise about. MgO-FeO-SiO2-CaO-Al2O3 system in the Earth’s lower mantle. A recent phase equilibrium study using a more representative composition of the mantle shows that Mg, Fe, and Al are mostly accommodated in orthorhombic (Mg,Fe)SiO3 perovskite and ferropericlase, (Mg,Fe)O. The Earth’s lower mantle may be composed mainly of aluminous (Mg,Fe)SiO3 perovskite, CaSiO3 perovskite, and ferropericlase. To gain an understanding of the structure and dynamics of the Earth’s lower mantle, it is important to investigate the elastic properties of these minerals under the pressure and temperature conditions found in this region. It is easy to investigate the physical properties of orthorhombic (Mg,Fe)SiO3 perovskite and ferropericlase, because both minerals can be recovered under ambient conditions. It is difficult to measure some of its physical properties

Methods

Results

Conclusion