First-principles prediction of the thermodynamic stability of xenon in monoclinic, tetragonal, and yttrium-stabilized cubic ZrO2

Fission product incorporation in ceramic fuels has long been an active area of research. In this work, we consider a special case of xenon incorporation in ZrO2 in the framework of closed systems under extreme radiation conditions where thermal defects are less important than cascade driven defects. The energetics of a variety of defect configurations associated with xenon incorporation are considered. We use first-principles density-functional theory (DFT) calculations to predict the thermodynamic stability of xenon in different ZrO2 structural forms, including monoclinic, tetragonal, and yttrium-stabilized cubic ZrO2. Two defect configurations are found to dominate the fission gas incorporation process: xenon interstitial and oxygen substitutional configurations. In yttrium-stabilized cubic ZrO2, the pre-existing structural oxygen vacancies provide ideal sites for Xe incorporation since no oxygen Frenkel pairs need to be formed. The charge-transfer issue in oxides modeling is important in defects calculations. This issue has also been addressed through our supercell benchmark calculations.