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Molecular dynamic simulation of helium diffusion within a ring dislocation inside stoichiometric UO2 nanocrystal was carried out. During the computational experiments (2.7 ns) in the temperature range from 525 to 1000 K, the dislocation was stable and the helium atom was contained inside the dislocation core. The magnitudes of the diffusion coefficient varied from 4.1·10–6 to 6.6·10–5 cm²/s. The diffusion process could be characterized by the constant activation energy ED = (0.25 ± 0.05) eV. [ABSTRACT FROM AUTHOR]

A model of uranium hexafluoride is suggested that is based on the empirical pair potentials of U-U, F-F, U-F used for both intra- and intermolecular interactions. The potentials for this model are obtained from the lattice parameters and the thermal expansion coefficient of UF6 crystal using the molecular dynamics simulation under the periodic boundary conditions with constant volume and temperature. Within the framework of the model, the thermal expansion and sublimation of crystalline UF6 are investigated. A set of potential parameters is identified that provides satisfactory simulation of both UF6 crystal and the dependence of the UF6 saturated vapor pressure on temperature. [ABSTRACT FROM AUTHOR]