The induced anisotropy in thermal conductivity of thorium dioxide and cerium dioxide

Abstract

The anisotropy in thermal conductivity (κ), induced by temperature gradient (TG), of thorium dioxide (ThO2) and cerium dioxide (CeO2) has been investigated by molecular dynamics (MD) simulations, in combination with non-equilibrium method, from 100 to 900 K. Anisotropy is observed in the systems with shorter length, in the direction of heat transfer, and is attributed to the large TG. The anisotropic response elevates with the increase in effective TG. Our results indicate that the higher temperature gradient is resulted from the significant phonon scattering, which in turn affects the transfer of thermal energy and leads to anisotropy in conductivity. It is found that the rate of change of thermal conductivity with TG is the largest for 〈1 0 0〉 crystallographic direction. At the highest TG, observed in this study, the anisotropy in thermal conductivity follows κ100 < κ110 < κ111. The effect of anisotropy reduces with the increase in temperature.