Thermal conductivities of ThO2, NpO2 and their related oxides: Molecular dynamics study

The thermal conductivities of ThO2, NpO2, (Th, U)O2, (Th, Pu)O2 and (U, Np)O2 have been investigated by molecular dynamics (MD) simulation up to 2000 K using the Busing-Ida potential function with partial ionic charges. In the present study, the thermal conductivity was calculated mainly by the Green-Kubo formula in the equilibrium MD scheme. The thermal conductivities of above actinide dioxides decreased with the increase of temperature due to the phonon-phonon interaction (Umklapp process). Concerning the composition of solid solutions, the decrease in thermal conductivity of (Th, Pu)O2 is great as compared to other ones. Various MD calculations elucidated that this result was caused by phonon scattering by lattice defects as additives rather than the phonon-phonon interaction, and that the lattice strain dominantly contributed to it.