Adsorption of water on UO2 (1 1 1) surface: Density functional theory calculations

The interaction between the surface of UO2 and molecular water is a serious concern in the range of nuclear waste management. We present a first-principle investigation of the interaction between water and UO2 (1 1 1) surface based on density functional (DFT) approach. The approximations of GGA and GGA + U were employed with the projector-augmented-wave method. Both stoichiometric and reduced surfaces were considered in our simulations. We study the atomic structures and adsorption energies of various configurations of water adsorption on UO2 (1 1 1) with water coverage of 0.25 ML. The mechanism of the interaction between water (molecular water and dissociated water) and the surface is discussed in detail. Comparing the adsorption energies for various configurations, both our GGA and GGA + U calculations suggested that molecular adsorption is more favored than dissociative adsorption of water on defect-free surface, while oxygen vacancy on the surface could make the adsorption of dissociated water more favorable. Our calculated results are in good agreement with reported experimental study and help comprehensive understanding of interactions between water and the stable UO2 (1 1 1) surface.