A microscopic model was developed for the high-temperature (2670K) phase transition to a superionic state. It was shown that self-consistent considerations of the point defects and electron sub-system interactions (leading to additional strong screening of the defect charges) in the mean-field approximation, and of the real symmetry of the oxide lattice, yielded satisfactory agreement of the model calculations with experimental data. This was true with regard to the degree of anion sub-lattice disorder and to the anomalous behaviour of the specific heat of the oxide in a certain temperature range.

Modelling of High-Temperature Superionic Transition of Uranium Dioxide Crystals. L.V.Matweev, M.S.Veshchunov: Journal of Nuclear Materials, 1998, 265[3], 285-94