A new empirical potential for simulating the formation of defects and their mobility in uranium dioxide

An empirical interaction potential has been developed primarily to simulate displacement cascades in a UO₂ matrix. After a bibliographical survey revealed that the potentials discussed in the literature are not entirely suitable for describing point defects and their migration, we decided to adapt the most representative of the existing potentials. Our objective was specifically to reproduce transport phenomena, which are fundamental to a satisfactory description of atomic displacement cascades. The modified potential more correctly describes the experimental energies of formation and migration of point defects (interstitials, vacancies, etc.) as well as the oxygen diffusion coefficients in the superionic phase. Thermal expansion, heat capacity and enthalpy are also better modelled over a wide temperature range. The new potential is much more transferable than earlier potentials fitted mainly to the properties of perfect crystals. The initial simulated atomic displacement cascades showed that this potential is well suited to the description of structural effects created by decelerating recoil nuclei in a UO₂ matrix.