Keywords:Lower mantle minerals, Lattice thermal conductivity, Solid solution effects of iron, Ab initio calculation
Determination of lattice thermal conductivity (κlat) 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 κlat 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 κlat remains unclear. We recently established an ab initio technique to compute κlat 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.