Abstract
Abstract Molecular dynamics modeling of uranium, plutonium, and thorium cation diffusion in the volume of isolated (U 0.25 Pu 0.5 Th 0.25 )O 2 nanocrystals consisting of 5460 particles was performed in the temperature range from 2700 K to 3200 K that corresponds to the superionic state. It was shown that cations of all types moved together during the passage of a cation vacancy through the crystal bulk. The temperature dependences of the diffusion coefficients of cations of all types coincided within the calculation error. The diffusion coefficient values lie in the region to which low-temperature experimental data on UO 2 and ThO 2 crystals can be extrapolated. The calculated value of the diffusion activation energy ( E D = 7.3 ± 0.8 eV) is somewhat overestimated relative to low-temperature measurements.