Transformation of electron density distribution induced by the cation point defects in uranium dioxide

The ab initio calculations on electronic structure of the large fragments of UO2 crystal lattice was performed using Molecular Dynamics and fully relativistic Discrete Variational method. The four types of clusters corresponding to stoichiometric crystal and to the crystals with isolated uranium vacancy and uranium interstitial impurity were considered. We investigated the transformation of valence and vacant bands and the nature of chemical bonding. The estimation of electron density redistribution among atoms of several coordination spheres around defects was performed. In contrast to previous ab initio and semi-empirical calculations, our model included the point symmetry of defects and the possibility of charge transfer between defects and all nearest and next nearest neighbors. We obtained that the deformation of crystal structure and the covalent interactions minimizes (or completely prevent) the electron density transfer between atoms in the vicinity of defects.