New insights into the process of intrinsic point defects in PuO 2 .

Intrinsic point defects are known to play a crucial role in determining the physical properties of solid-state materials. In this study, we systematically investigate the intrinsic point defects, including vacancies (V Pu and V O ), interstitials (Pu i and O i ), and antisite atoms (Pu O and O Pu ) in PuO 2 using the first-principles plane wave pseudopotential method. Our calculations consider the whole charge state of these point defects, as well as the effect of oxygen partial pressure. This leads to a new perspective on the process of intrinsic point defects in PuO 2 . We find that the antisite atoms O Pu and Pu O are more likely to appear in O-rich and O-deficient environments, respectively. Interestingly, the most energetically favorable type of Schottky defect is {2V Pu 3- : 3V O 2+ } in an O-rich environment, while {4V O 1+ : V Pu 4- } is preferred in an O-deficient environment. These results differ from the commonly known {V Pu 4- : 2V O 2+ } type of Schottky defect. Moreover, under O-deficient conditions, we predict that the stable cation Frenkel defect is {V Pu 4+ : Pu i 4+ }, while the most stable anion Frenkel defect is {V O 2+ : O i 2- } under O-rich conditions. Lastly, we find that the only two types of antisite pairs that can appear are {O Pu 5- : Pu O 5+ } and {O Pu 6- : Pu O 6+ }, with the latter being the more stable configuration. These unconventional defect configurations provide a new viewpoint on the process of intrinsic point defects in PuO 2 and lay theoretical foundations for future experiments.