Molecular dynamics study on planar clustering of xenon in UO₂

Interatomic potentials of uranium dioxide are investigated on their applicability to model structural stabilities beyond fluorite phase by comparing with ab initio results. A high pressure cotunnite phase and loosely stacking virtual crystal are involved in order to get a primary confidence for large-scale deformation modelings of UO₂ under irradiation damages. The behavior of Xe atoms in UO₂ fuel is studied with molecular dynamics simulations. Besides the ground state bubble geometry, we find that a planar distribution is also (meta-)stable for xenon under thermodynamic perturbations. The Xe atoms with a planar configuration are in a liquid state at a typical reactor temperature of 1000 K, which presents a modulated layer-structure near the interface with solid UO₂. A planar defects loop remains after these Xe atoms are released out.