The dynamical simulation of superionic UO2 using shell-model potentials

Shell-model molecular dynamics simulation is used to study solid UO2 in the temperature range 250–3100 K where experiments indicate that the material is a superionic conductor. The simulations are based on the interaction models of Jackson et al., and have been used to calculate the temperature-dependent oxygen diffusion coefficient, the spatial distribution of oxygen, and the dynamical structure factors. We find a liquid-like diffusion coefficient and rapidly increasing oxygen disorder in this temperature range. Detailed comparisons with experimental diffusion data and with neutron diffraction and quasi-elastic measurements show that the simulations reproduce the behaviour of the real material with semi-quantitative accuracy.