The environmental dependence of redox energetics of PuO2 and α-Pu2O3: A quantitative solution from DFT+U calculations
Bo Sun, Haifeng Liu, Haifeng Song, Guang-Cai Zhang, Hui Zheng, Xian-Geng Zhao, Ping Zhang
Abstract
We report a comprehensive density functional theory (DFT) +
U
study of the energetics of charged and neutral oxygen defects in both PuO
2
and
α
-Pu
2
O
3
, and present a quantitative determination of the equilibrium compositions of reduced PuO
2
(PuO
2−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 PuO
2
to
α
-Pu
2
O
3
is found to be facilitated by accompanying volume expansion of PuO
2−x
and the possible migration of O-vacancy, whereas further reduction of
α
-Pu
2
O
3
is predicted to be much more difficult. In contrast to the endothermic oxidation of PuO
2
,\ the oxidation of
α
-Pu
2
O
3
is a stable exothermic process.