Electronic structure and effective charges on atoms near anion point defects in uranium dioxide

Abstract

The computer modeling of electronic structure and electron density distribution in the large fragments of crystal lattices of uranium dioxide was carried out using Molecular Dynamics and ab initio Relativistic Discrete Variational method (RDV). The five types of clusters with oxygen vacancy and metal and oxygen atoms in the center were considered. At the first step of simulation, the geometry of clusters corresponded to the regular crystals, and at the second step, the distorted structures around one oxygen vacancy and one oxygen interstitial point defects were considered. In each case, the transformation of electronic states and chemical bonding were investigated, as well the estimation of effective charges on atoms of several coordination spheres around defects was performed. For the calculations of atomic charges we used the original procedure based on spatial integration of electron density. Unlike previous simulations ignoring point symmetry of isolated defects, our model included the charge transfer between defects and all nearest and next nearest neighbors. Our study showed that the transfer of electron density between atoms around defects is more complex than that predicted in previous calculations using ab initio and pair-potential models.