２１世紀に向けた結晶学の新たな挑戦 ５． 地球内部を知る マントル内地震波不連続面の構造と物性の計算機シミュレーション

Abstract

Molecular dynamics (MD) simulation is used to predict the structure and elasticity of MgO, MgSiO3 perovskite, and the olivine, modified-spinel, and spinel forms of Mg2SiO4 at high temperatures and high pressures, found in the deep Earth. In order to take account of noncentral forces in crystals, the breathing shell model (BSM) is used for simulation, in which the repulsive radii of O ions are allowed to deform isotropically under the effects of other ions in the crystal. For each phase, the MD simulation with BSM is found to be very successful in reproducing accurately the observed structural and elastic properties over wide temperature and pressure ranges. We then apply MD simulation to predict the density and seismic velocity contrasts at the 410 km and 660 km discontinuities in the Earth's mantle, and compare the simulated results with seismologically observed data.