| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1295439 | Solid State Ionics | 2014 | 5 Pages |
•Lowest energy vacancy migration requires reconfiguration of lowest energy cluster.•Charge balancing defects have a major effect on activation energy barrier.•Many configurations have more favourable migrations than the low energy cluster.•Stoichiometry has a major effect on the number of possible cluster arrangements.•The number of possible migration mechanisms affects Arrhenius pre-exponential term.
The effect of cluster configuration on vacancy mediated uranium migration is investigated for stoichiometric UO2 and hyper-stoichiometric UO2+x. The minimum enthalpy pathway involves reconfiguration of the most stable cluster to a metastable configuration, in stoichiometric and hyper-stoichiometric systems. Additionally, a much larger number of alternative metastable configurations were identified for UO2+x compared to UO2. This would lead to a larger contribution to the Arrhenius pre-exponential term with hyper-stoichiometry. Consequently, the often made assumption that re-orientation of the ground state cluster offers access to the migration activation energy cannot be assumed to be valid.
