The environmental dependence of redox energetics of PuO2 and α-Pu2O3: A quantitative solution from DFT+UDFT+U

We report a comprehensive density functional theory (DFT)+U(DFT)+U study of the energetics of charged and neutral oxygen defects in both PuO2 and α-Pu2O3, and present a quantitative determination of the equilibrium compositions of reduced PuO2 (PuO2 − x) as functions of environmental temperature and partial pressure of oxygen, which shows fairly agreement with corresponding high-temperature experiments. Under ambient conditions, the endothermic reduction of PuO2 to α-Pu2O3 is found to be facilitated by accompanying volume expansion of PuO2 − x and the possible migration of O-vacancy, whereas further reduction of α-Pu2O3 is predicted to be much more difficult. In contrast to the endothermic oxidation of PuO2, the oxidation of α-Pu2O3 is a stable exothermic process.

► We provide defect physics study. ► A quantitative study of PuO2 − x phase is presented. ► We provide detailed redox property.