The derivation of thermo-physical properties and phase equilibria of silicate materials from lattice vibrations: Application to convection in the Earth’s mantle

We used a lattice vibrational technique to derive thermophysical and thermochemical properties and phase equilibria in the system Mg2SiO4. The technique is based on an extension of Kieffer’s model to incorporate details of the phonon spectrum, and it includes treatment of intrinsic anharmonicity. We show that anharmonicity significantly impacts phase boundaries and sound velocities, and demonstrate that the technique discriminates better between experimental data relative to traditional Calphad techniques. We show that calculated thermophysical properties are anomaly free in pressure–temperature space up to core–mantle-boundary conditions in the Earth. Our technique has been applied to a mantle convection experiment to simulate material transport in global thermal convection of a Mg2SiO4 earth mantle. Preliminary results indicate a low degree of layering in mantle flow near 660 km depth in the earth and strong lateral variation of the post-perovskite layer near the bottom of the mantle.