Ab initio lattice thermal conductivity of (Mg,Fe)O ferropericlase at the Earth's lower mantle pressure and temperature

The effects of iron (Fe) incorporation on the lattice thermal conductivity (K-lat) of MgO are investigated under the Earth's lower mantle pressure (P) and temperature (T) condition (P > similar to 20 GPa, T > similar to 2000 K) based on the density-functional theory combined with the anharmonic lattice dynamics theory. The K-lat of ferropericlase (FP) is determined combining the internally consistent LDA + U method and self-consistent approach to solve the phonon Boltzmann transport equation. The calculated.lat are well fitted to the extended Slack model which is proposed in this study to represent.lat in a wide volume and T range. Results demonstrate that the K-lat of MgO decreases strongly by Fe incorporation. This strong negative effect is found due to decreases in phonon group velocity and lifetime. Consequently, the.lat of MgO at the core-mantle boundary condition (P similar to 136 GPa, T similar to 4000 K) is substantially reduced from similar to 40 to similar to 10 W m(-1) K-1 by the incorporation of Fe (12.5 mol%). The effect of Fe incorporation on the.lat of MgO is found to be insensitive to P and T, and at high T, the.lat of FP obeys a well-established T inverse relation unlike the experimental observations.