[S-IT22] [EE] 核-マントルの相互作用と共進化

[SIT22-P24] Ab initio lattice thermal conductivity of MgO using a full solution to the linearized Boltzmann transport equation

*出倉 春彦¹、土屋 卓久¹ (1.愛媛大学地球深部ダイナミクス研究センター)

キーワード：Lower mantle minerals, Lattice thermal conductivity, Computer simulation, Phonon-phonon interaction, Density-functional theory

Lattice thermal conductivity, κ_lat, of MgO at high pressures and temperatures, up to 150 GPa and 4000 K, are determined using lattice dynamics calculations and the linearized phonon Boltzmann transport equation (BTE) beyond the relaxation time approximation (RTA) from first principles. It is found that the complete solution of the linearized BTE substantially corrects values of κ_lat calculated with the RTA by ~30%, from ~39 W m⁻¹ K⁻¹ to ~50 W m⁻¹ K⁻¹ under ambient conditions. The calculated values of κ_lat are in good agreement with those from the existing experiments. At conditions representative of the Earth’s core-mantle boundary (P = 136 GPa and T = 3800 K), κ_lat is predicted to be ~31 W m⁻¹ K⁻¹ and ~39 W m⁻¹ K⁻¹ by RTA and the full solution of BTE, respectively. We report a detailed comparison of our study with earlier theoretical studies.