  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.
