Molecular Dynamics Simulation of MgSiO₃ Perovskite

Using molecular dynamics to simulate MgSiO₃ perovskite is performed to investigate its phase transitions and superionicity. These simulations has used parameter-free Gordon-Kim potentials and a novel technique to monitor the motion of ions which clearly demonstrates the sublattice melting of ions O^2- and the rotations of SiO₆ octahedra. MgSiO₃ has to undergo a few of phase transitions, then enter into the cubic phase. In particular, there is a transitional phase between orthorhombic phase and cubic phase. There are a superionc phase and the cubic phase in magnesium-rich silicate perovskite. This superionic phase occurs after the onset of cubic phase before the melting point. The onset temperature T_c for superionicity is about 200-700K below the melting point T_m, T_c/T_m ~0.92.