Lattice Thermal Conductivity of MgSiO3 Perovskite and Post-Perovskite under Lower Mantle Conditions Calculated by Deep Potential Molecular Dynamics

Lattice thermal conductivity (kappa (lat)) of MgSiO3 perovskite and post-perovskite is an important parameter for the thermal dynamics in the Earth. Here, we develop a deep potential of density functional theory quality under entire thermodynamic conditions in the lower mantle, and calculate the kappa (lat) by the Green-Kubo relation. Deep potential molecular dynamics captures full-order anharmonicity and considers ill-defined phonons in low-kappa (lat) materials ignored in the phonon gas model. The kappa (lat) shows negative temperature dependence and positive linear pressure dependence. Interestingly, the kappa (lat) undergos an increase at the phase boundary from perovskite to post-perovskite. We demonstrate that, along the geotherm, the kappa (lat) increases by 18.2% at the phase boundary. Our results would be helpful for evaluating Earth's thermal dynamics and improving the Earth model.