Calculation of defect formation energies in UO2

ABSTRACTWe present a physically justified formalism for the calculation of defect formation energies in UO2. The accessible ranges of chemical potentials of the two components U and O are calculated using the U-O experimental phase diagram and a constraint on the formation energies of vacancies. We then apply this formalism to the DFT+U investigation of the monovacancies and monointerstitials in UO2.The results of the most stable charge states of these defects are consistent with a strongly ionic system. Calculations predict similarly low formation energies for $V_U^{4 - }$ and $I_O^{2 - }$ in hyperstoichiometric UO2.