[SIT22-P17] Ab initio lattice thermal conductivity of MgSiO3 post-perovskite
キーワード：下部マントル鉱物、格子熱伝導率、第一原理計算
Lattice thermal conductivity (κlat) 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 κlat of PPv but only at 300 K, far from the mantle temperature. On the other hand, the κlat 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 κlat of PPv under the lowermost mantle P,T are inconsistent with each other. We recently established an ab initio technique to compute κlat 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, κlat 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 κlat 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 κlat of PPv on the heat flux will also be discussed.