The incorporation and solution of krypton in uranium dioxide: Density functional theory calculations

Ab initio calculations based on density functional theory have been carried to investigate the incorporation and solution of krypton in uranium dioxide. The GGA and GGA + U approximations were used with the projector-augmented-wave method. Several defects that are likely to accommodate the incorporation of krypton in UO2, such as oxygen and uranium vacancy, divacancy and Schottky defects were considered in this work. Both our SP-GGA and SP-GGA + U calculations suggested that the lowest incorporation energy corresponds to the divacancy. With SP-GGA method, the solution energies are positive whatever the trapping site considered, which confirms that Kr atoms are insoluble in UO2, but notable discrepancy exits between the results calculated by SP-GGA + U and SP-GGA. We highlight that the use of SP + GGA + U significantly increases the number of the energy minima of the system. Furthermore, the concentrations of the point defects and the solution energy of Kr for the different incorporation sites as a function of the stoichiometry were also obtained when the deviation from stoichiometry is small.