Plane-wave pseudopotential study of point defects in uranium dioxide - art. no. 104107

A study on uranium and oxygen point defects in uranium dioxide using the ab initio plane-wave pseudopotential method in the local density approximatio n of the density functional theoretical framework is presented. Norm conser ving pseudopotentials are used to describe oxygen and uranium atoms. The ur anium pseudopotential is specifically described. Its validity is ascertaine d thanks to a detailed structural study of uranium dioxide and of three pha ses of metallic uranium (fcc, bcc, and a phase). The free energies of forma tion of both intrinsic (Frenkel pairs and Schottky defect) and extrinsic (s ingle vacancies or interstitials) defects are calculated. The obtained valu es form a reliable set of numerical data that are analyzed in the framework of the point defect model which is commonly used to assess defect concentr ations in uranium dioxide and their variation with stoichiometry. From the obtained results, the ability of the point defect model to accurately repro duce defect concentrations in uranium dioxide is discussed.