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

[SIT22-15] Effects of iron on the lattice thermal conductivity of lower mantle minerals evaluated by Ab initio anharmonic lattice dynamics simulations

*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, Solid solution effects of iron, Ab initio calculation

Determination of lattice thermal conductivity (κ_lat) of lower mantle (LM) minerals is a key to understanding the dynamics and evolution of the earth’s deep interior. Some recent experimental studies have shown that κ_lat of MgO and MgSiO₃ are substantially reduced by Fe incorporation (Manthilake et al., 2012; Goncharov et al., 2015; Ohta et al., 2017; Hsieh et al., 2017); Okuda et al. (2017) reported very weak effects on MgSiO₃ at lowermost mantle pressure. So, experimental results are still largely scattered and effects on Fe in κ_lat remains unclear. We recently established an ab initio technique to compute κ_lat of Fe-free systems 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, the technique is extended further to Fe-bearing systems, (Mg,Fe)SiO₃ bridgmanite (Brg) and (Mg,Fe)O ferropericlase (FP), combined with the internally consistent DFT+U technique (Wang et al., 2015). Calculations demonstrate strong solid solution effects in both Brg and FP. The effects of Fe are found to be caused mainly by the substantial changes in harmonic properties.