MOLECULAR-DYNAMICS OF MGSIO3 PEROVSKITE AT HIGH-PRESSURES - EQUATION OF STATE, STRUCTURE, AND MELTING TRANSITION

Molecular dynamics (MD) simulations of MgSiO3-perovskite and melt with the MATSUI (1988) interatomic potential are used to resolve the problem of inconsistency between modeled and experimental melting curves. Equations of state for solid and liquid MgSiO3-perovskite are in agreement with experimental data and are useful for calculating densities at experimentally inaccessible temperatures and pressures. Comparison with the Preliminary Earth Model (DZIEWONSKI and ANDERSON, 1981) shows that the equation of state of MgSiO3-perovskite is consistent with seismic parameter for lower mantle. Two-phase MD simulations at constant pressure were also performed to calculate a melting curve of MgSiO3-perovskite in agreement with the recent experiments. Overheating does not exceed 400 K in accord with the theoretical estimate for finite systems. Extrapolation of meltings temperature to the core-mantle boundary pressure (134 GPa) with the Simon equation gives temperature of approximate to 6400 K for MgSiO3-perovskite and shows that, according to accepted estimates of temperature at core-mantle boundary, MgSiO3-perovskite remains solid.