A study was made of U and O point defects by using the ab initio plane-wave pseudopotential method in the local density approximation of the density functional framework. Norm-conserving pseudopotentials were used to describe O and U atoms. The U pseudopotential in particular was described, and its validity was determined via a detailed structural study of the dioxide and of 3 phases (face-centered cubic, body-centered cubic, α) of metallic U. The free energies of formation of intrinsic (Frenkel pair, Schottky) and extrinsic (single vacancy or interstitial) defects were calculated. These values constituted a reliable set of numerical data which were analyzed within the framework of the point defect model that was generally used to treat defect concentrations in UO2, and their variation with stoichiometry. On the basis of these results, the ability of the point defect model to predict defect concentrations accurately was assessed.

Plane-Wave Pseudopotential Study of Point Defects in Uranium Dioxide. J.P.Crocombette, F.Jollet, L.T.Nga, T.Petit: Physical Review B, 2001, 64[10], 104107 (12pp)