Charge states of point defects in plutonium oxide: A first-principles study

The stability of charged defects in PuO2 are systematically investigated by quasi-annealing simulations based on local spin density approximation (LSDA) + U calculations. The formation energies of intrinsic (Frenkel and Schottky pairs) and extrinsic (single vacancy or interstitial) defects at different charged states are calculated and presented. According to our results, the noninteracting oxygen Frenkel pairs made of the association of doubly charged defects are the most favorable form of intrinsic defects, the formation energy of which is in good agreement with experimental values. The negative charged oxygen interstitial ( I O 2 − ) and positive charged oxygen vacancy ( V O 2 + ) defects have the lowest formation energies at oxygen-rich and oxygen-poor environments, respectively, and thus are the most commonly seen extrinsic defects. Both the existences of oxygen vacancy and oxygen interstitial induce new electronic states in the band gap of stoichiometric PuO2, showing doping effects.