First-Principles Energetics of Some Nonmetallic Impurity Atoms in Plutonium Dioxide

Abstract

The energetics of some typical nonmetallic impurity atoms (H, He, B, C, N, O, F, Ne, Cl, Ar, Kr, and Xe) in PuO2 are calculated using a projector augmented-wave method under the framework of density functional theory. The Hubbard parameter U and van der Waals corrections are used to describe the strongly correlated electronic behavior of f electrons in Pu and weak interactions of rare gases, respectively. Three incorporation sites of impurity atoms, that is, octahedral interstitial, O vacancy, and Pu vacancy sites, are considered. The results indicate that the energetics of impurity atoms depend significantly on the incorporation sites and on atomic properties such as atomic radius and electron affinity. Almost all impurity atoms considered here are energetically unfavorable at the three incorporation sites, with the exception of the F atom at the octahedral interstitial and O vacancy sites. The trends of incorporation energies of rare gas atoms generally reflect a size effect. Furthermore, charge-transfer analysis reveals that the valence electrons can be polarized more easily with increasing atomic number of rare gas elements. Finally, electronic structures of these systems containing impurity atoms also exhibit general trends in their relative stability and chemical bonding character.