Point Defect and Impurity Incorporation in Plutonium Oxides

The incorporation of point defects and impurities in materials is vital for understanding their properties, stability, and performance. The stability of metallic plutonium is largely governed by the permeability of its heterogeneous surface oxide, which typically adopts the stoichiometry of PuO₂ or Pu₂O₃. Here, we use hybrid density functional theory calculations to compute formation energies and kinetic barriers of migration for native point defects and common environmental contaminants in PuO₂. Oxygen vacancies and small polarons form readily in PuO₂, while nitrogen-, fluorine-, and hydrogen-based impurities can also be favorable under certain conditions. Oxygen vacancies and hydrogen interstitials are highly mobile, but their prevalence depends on the chemical potential conditions. Accordingly, monitoring the prevalence of these species is key for maintaining the stability of plutonium and its native surface oxide.