  The incorporation of oxygen atoms has been simulated into either nitrogen or
uranium vacancy at the UN(001) surface, sub-surface or central layers. For
calculations on the corresponding slab models both the relativistic
pseudopotentials and the method of projector augmented-waves (PAW) as
implemented in the VASP computer code have been used. The energies of O atom
incorporation and solution within the defective UN surface have been calculated
and discussed. For different configurations of oxygen ions at vacancies within
the UN(001) slab, the calculated density of states and electronic charge
re-distribution was analyzed. Considerable energetic preference of O atom
incorporation into the N-vacancy as compared to U-vacancy indicates that the
observed oxidation of UN is determined mainly by the interaction of oxygen
atoms with the surface and sub-surface N vacancies resulting in their capture
by the vacancies and formation of O-U bonds with the nearest uranium atoms.
Keywords: Density functional calculations, uranium mononitride, surface,
defects, N and U vacancies

Materials Science;Computational Physics