Molecular dynamics simulation of premelting and melting phase transitions in stoichiometric uranium dioxide

Results of molecular dynamics (MD) simulation of U O 2 in a wide temperature range are presented and discussed. A new approach to the calibration of a partly ionic Busing-Ida-type model is proposed. A potential parameter set is obtained reproducing the experimental density of solid U O 2 in a wide range of temperatures. A conventional simulation of the high-temperature stoichiometric U O 2 on large MD cells, based on a novel fast method of computation of Coulomb forces, reveals characteristic features of a premelting λ transition at a temperature near to that experimentally observed ( T λ = 2670 K ) . A strong deviation from the Arrhenius behavior of the oxygen self-diffusion coefficient was found in the vicinity of the transition point. Predictions for liquid U O 2 , based on the same potential parameter set, are in good agreement with existing experimental data and theoretical calculations.