Lattice thermal conductivity of CaSiO3 under high pressure

The structural phase transitions and thermal conductivity of minerals are crucial for exploration the physical and chemical properties of the Earths interior and its dynamic evolution. Understanding these properties allows scientists to build more accurate models of the Earth's interior and its geodynamic behavior. Here, we conduct extensively structural searches of ${\mathrm{CaSiO}}_{3}$ under high pressure by CALYPSO method and first-principles calculations. Several stable phases of ${\mathrm{CaSiO}}_{3}$ are uncovered, which are in good agreement with the previous experiments. The lattice thermal conductivities of ${\mathrm{CaSiO}}_{3}$ minerals are found to decrease with the increases of temperature and pressure. Under geothermal gradient conditions, the thermal conductivities of the $P\overline{1}$ (3 GPa, 900 K), $Pnma$ (14 GPa, 1800 K), $I4/mcm$ (24 GPa, 2000 K), and $I4/mcm$ (136 GPa, 3000 K) phases of ${\mathrm{CaSiO}}_{3}$ are calculated to be 0.94, 0.11, 0.05 and 0.03 $\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}{\mathrm{K}}^{\ensuremath{-}1}$, respectively. However, after considering the two-channel model corrections, these thermal conductivities are increased to 2.57, 1.01, 1.70 and 2.97 $\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}{\mathrm{K}}^{\ensuremath{-}1}$, respectively. Interestingly, the $I4/mcm$ phase exhibits an unexpected behavior, showing the enhancements in thermal conductivities with the increases of temperature and pressure. The anomalous increase of thermal conductivities are derived from dual in-plane vibrations of oxygen atoms in the Si-O octahedra. Our findings provide valuable insights to understand the heat transfer mechanisms and the mantle convection dynamics of the Earth.