First-principles study of the lattice thermal conductivity of Akimotoite in the mantle transition zone

The lattice thermal conductivity ( ) of mantle minerals plays a crucial role in the heat flow and temperature distribution within the Earth. Akimotoite is stable at the bottom of the mantle transition zone and transit to MgSiO3 perovskite (MgPv). In this work, we carry out a study on the of akimotoite for pressures up to 25 GPa and temperatures up to 2500 K based on first-principles calculations combined with lattice dynamics theory. At 300 K and 25 GPa, the of akimotoite is 37.66 W m–1 K–1 and larger than that of MgPv (13.46 W m–1 K–1), which implies that the phase transition results in the reduction in . At 300 K, the pressure dependence of is 0.68 W m–1 K–1 GPa-1 and stronger than that of MgPv (0.48 W m–1 K–1 GPa-1). The azimuthal anisotropy in of akimotoite decreases from 45.5% at 0 GPa to 28.94% at 25 GPa, while the variation trend is opposite to that of MgPv. The incorporation of Fe decreases the and increases the anisotropy of akimotoite. Along the geotherm, the of akimotoite is lower than that of ringwoodite, which would slow down the heat conduction at the bottom of mantle transition zone. These findings are useful for determining the thermal structure, and understanding heat transfer, in the interior of the Earth.