Modelling of high temperature superionic transition of uranium dioxide crystals

A microscopic model of the high temperature (T ∼ 2670 K) phase transition of uranium dioxide crystals to the super-ionic state is developed. It is shown that the self-consistent consideration of the point defects and the electron subsystem interactions (leading to additional strong screening of the defect charges) in the 'mean-field' approximation and the real symmetry of the UO2 crystalline lattice afford satisfactory agreement of the model calculations with experimental data on the degree of the anion sublattice disorder and an anomalous behaviour of the specific heat of uranium dioxide in the given temperature range. (orig.)