First-Principles Calculations of PuO 2 ± x

Abstract

The electronic structure of PuO 2 ± x was studied using first-principles quantum mechanics, realized with the self-interaction corrected local spin density method. In the stoichiometric PuO 2 compound, Pu occurs in the Pu(IV) oxidation state, corresponding to a localized f 4 shell. If oxygen is introduced onto the octahedral interstitial site, the nearby Pu atoms turn into Pu(V) (f 3 ) by transferring electrons to the oxygen. Oxygen vacancies cause Pu(III) (f 5 ) to form by taking up electrons released by oxygen. At T = 0, the PuO 2 compound is stable with respect to free oxygen, but the delicate energy balance suggests the possible deterioration of the material during long-term storage.