The incorporation and migration of a single xenon atom in ceria

The behavior of xenon gas is crucial for the performance of nuclear fuel materials. We report molecular statics calculation results for the characteristics of a single xenon atom in cerium oxide, a non-radioactive surrogate of uranium dioxide. A variety of possible xenon incorporation sites, including the octahedral interstitial position, single-Ce-vacancy clusters, and double-Ce-vacancy clusters were considered. The binding energies and corresponding xenon incorporation energies were computed to reveal the preferred xenon positions in ceria. Different migration mechanisms of single xenon atoms were found to be involved with various incorporation sites. The energy barriers of all possible migration pathways were calculated. Only the mobility of single xenon atoms in the double-Ce-vacancy sites, which is due to the vacancy-assisted xenon migration, can account for the xenon diffusivity implied by bubble formation observed in experiments. The results also validated the role of ceria as a reliable surrogate of uranium dioxide in studies involving xenon gas.