The effects of iron (Fe) incorporation on the lattice thermal conductivity (κlat) of MgO are investigated under the Earth's lower mantle pressure (P) and temperature (T) condition (P> ∼20 GPa,T> ∼2000 K) based on the density-functional theory combined with the anharmonic lattice dynamics theory. Theκlatof ferropericlase (FP) is determined combining the internally consistent LDA +Umethod and self-consistent approach to solve the phonon Boltzmann transport equation. The calculatedκlatare well fitted to the extended Slack model which is proposed in this study to representκlatin a wide volume andTrange. Results demonstrate that theκlatof MgO decreases strongly by Fe incorporation. This strong negative effect is found due to decreases in phonon group velocity and lifetime. Consequently, theκlatof MgO at the core-mantle boundary condition (P∼ 136 GPa,T∼ 4000 K) is substantially reduced from ∼40 to ∼10 W m-1K-1by the incorporation of Fe (12.5 mol%). The effect of Fe incorporation on theκlatof MgO is found to be insensitive toPandT, and at highT, theκlatof FP obeys a well-establishedTinverse relation unlike the experimental observations.
Keywords: (Mg,Fe)O ferropericlase; anharmonic lattice dynamics; deep earth interior; first-principles computation; high-pressure and high-temperature; lattice thermal conductivity.
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