Critical Assessment of UO₂ Classical Potentials for Thermal Conductivity Calculations

This article reviews the thermal transport properties as predicted by 26 classical interatomic potentials for uranium dioxide, an important nuclear fuel material, determined using a lattice dynamics-based method. The calculations reveal structural instabilities for multiple potentials, as well as the presence of lower energy structures even for potentials in which the fluorite structure is stable. Both rigid atom and shell model potentials are considered, and general trends in their representation of the thermal conductivity are identified. Reviewed classical potentials predict thermal conductivity in the range of ~5-22 W/mK, compared to the experimental value of 8.9 W/mK. The quality of the anharmonicity correction that is based on the correlation between thermal expansion and thermal conductivity is investigated, and it found to generally improve thermal conductivities results.