An atomistic model of MgSiO3 perovskite and post-perovskite phases

A classical force field for MgSiO3 polymorphs is presented and tested for the perovskite, post-perovskite and enstatite phases. In this force field each ion has a fixed partial charge and a fixed polarizability and the potential energy is minimised with respect to the ions' dipole moments at each step of molecular dynamics by iterating them to self-consistency. The potential parameters are obtained by fitting to forces, stresses and energies calculated by density functional theory. The phase transition from perovskite to post-perovskite is predicted to take place at a pressure of 60 GPa at zero temperature. The potential reproduces well structural and thermodynamic properties as well as defects formation in a wide range of pressures, and therefore will be useful for the investigation of MgSiO3 based materials in a geophysical context. (C) 2016 Elsevier B.V. All rights reserved.