Density-functional theory investigation of oxidative corrosion of UO2

► Oxidation of UO2 (1 1 1) surface as a function of temperature and oxygen pressure. ► DFT and ab initio thermodynamics quantify oxidation of UO2 lattice. ► Surface uranyl group form at low temperature and are stable above 1000 K. ► High density of subsurface interstitial oxygen causes lattice contraction. ► Electrons transfer from local U 5f band to oxygen interstitial 2p band.