Lattice Thermal Conductivity of MgSiO3 Postperovskite Under the Lowermost Mantle Conditions From Ab Initio Anharmonic Lattice Dynamics

摘要

The lattice thermal conductivity (kappa(lat)) of MgSiO3 postperovskite (Mg-PPv) under the lowermost mantle pressure (P) and temperature (T) conditions was calculated using density functional theory combining anharmonic lattice dynamics theory. The kappa(lat) of Mg-PPv was found to be similar to 50% higher than that of MgSiO3 bridgmanite (Mg-Brg) owing to the larger phonon group velocity and lifetime. The lateral variation in the core-mantle boundary heat flux (q(CMB)) can be enhanced by the Brg-PPv phase transition. We also found that the kappa(lat) along the c axis of Mg-PPv is close to the conductivity of isotropic aggregate. This suggests that the effect of anisotropy in the kappa(lat) on q(CMB) would be minor if the transversely isotropic aggregate with the c axis vertical alignment, a potential source of seismic anisotropy in the D '' layer, is developed.