Anharmonic specific heat of solid UO2

The specific heat of UO2 and related fluorite crystals contains a contribution from the anharmonic motion of the anion. We evaluate this term using thermodynamic perturbation theory and known parameters from neutron experiments. It is negligible (less than 2% of the total observed) up to 1273 K for UO2, the highest temperatures for which anharmonicity parameters are known. Extension of the scattering experiments to higher temperatures will be necessary before anharmonic contributions to the specific heat anomaly can be assessed reliably and their importance relative to other conjectured mechanisms, notably electronic disorder, adjudged.