First-principles calculation of the lattice thermal conductivity of the lower mantle

Abstract:

The thermal conductivity of the lower mantle has important implications for the thermal structure of the Earth’s interior. Estimates of the thermal conductivity of the most abundant phases, at core-mantle boundary conditions vary widely. We performed ab initio simulations to determine the lattice thermal conductivity of MgSiO₃ perovskite, finding a value of about 7 ± 1 W m⁻¹ K⁻¹ at core–mantle boundary conditions, consistent with geophysical constraints for the thermal state at the base of the mantle. We find that lattice thermal conductivity depends strongly on pressure, explaining the dynamical stability of super-plumes, but weakly with temperature and composition. Our results show evidence of saturation, at lower mantle temperatures, as the phonon mean free path approaches the interatomic spacing. Combining our results with seismic tomography, we predict large lateral variations in the heat-flux from the core that could have important implications for core dynamics.