Lattice thermal conductivity of Mg2SiO4 olivine and its polymorphs under extreme conditions

Abstract

The thermal transport properties of minerals at high temperature and high pressure are important for understanding the internal evolution and dynamic processes of the Earth. Here, we carry out a detailed study on the lattice thermal conductivities (\({\kappa }_\text {latt}\)) of \(\text {Mg}_2\text {SiO}_4\) under upper mantle and transition zone conditions by anharmonic lattice dynamics method. The calculations show that the \({\kappa }_\text {latt}\) of \(\text {Mg}_2\text {SiO}_4\) increase with the phase transitions, which agree with the previous measurements and are attributed to the increase of lifetime and group velocity under extreme conditions. The \({\kappa }_\text {latt}\) of \(\text {Mg}_2\text {SiO}_4\) along the geotherm shows a 64\(\%\) jump at 410 \({\textrm{km}}\) and 71\(\%\) jump at 520 \(\textrm{km}\). The anisotropy in the \({\kappa }_\text {latt}\) of olivine and wadsleyite decreases with increasing pressure. The present findings offer a fundamental knowledge of the \({\kappa }_\text {latt}\) of \(\text {Mg}_2\text {SiO}_4\) under extreme conditions, which are crucially important for understanding the thermal transport processes in the Earth.