[S-IT22] Interaction and Coevolution of the Core and Mantle in the Earth and Planets

[SIT22-P17] Ab initio lattice thermal conductivity of MgSiO₃ post-perovskite

*Haruhiko Dekura¹, Taku Tsuchiya^1,2 (1.Geodynamics Research Center, Ehime University, 2.Earth-Life Science Institute, Tokyo Institute of Technology)

Keywords:Lower mantle minerals, Lattice thermal conductivity, Ab initio calculation

Lattice thermal conductivity (κ_lat) of the lowermost mantle (D'' layer) is one of the key properties controlling the thermal evolution of the Earth and MgSiO₃ post-perovskite (PPv) is believed to be the most abundant mineral in this region. Ohta et al. (2012) measured the κ_lat of PPv but only at 300 K, far from the mantle temperature. On the other hand, the κ_lat of PPv was computed under lowermost mantle P,T (Haigis et al., 2012; Ammann et al., 2014) but using interatomic model potentials with adjustable parameters. Reported κ_lat of PPv under the lowermost mantle P,T are inconsistent with each other. We recently established an ab initio technique to compute κ_lat based on the density-functional theory (DFT) combined with fully solving the phonon Boltzmann transport equation, which was successfully applied to MgO (Dekura and Tsuchiya, 2017). In this study, using this technique, κ_lat of PPv is calculated under the lowermost mantle condition, and it is found ~20% lower than those reported in the model potential studies. We also find that the κ_lat of PPv is ~50% larger than that of Brg. This indicates that the lateral variations in the core-mantle boundary heat flux would be enhanced by the Brg-PPv phase transition. Effects of anisotropy in the κ_lat of PPv on the heat flux will also be discussed.