Density functional theory study of adsorption of H2O on γ-U(110) surface

The adsorption and dissociation of H2O on gamma-U(110) surface have been studied using density functional theory calculations. For molecular adsorption, the water molecules prefer to be adsorbed parallelly on the top site. The adsorption energy of 2.06 eV and charge transfer between H2O and the surface suggest that chemical adsorption has taken place. The hybridization between 6d orbitals of surface uranium and 2p orbitals of oxygen in H2O plays a dominant role in the chemical adsorption model. Compared with molecular adsorptions, the H2O in gamma-U(110) surface was found to be more prone to dissociative adsorptions. The adsorbed H2O can easily dissociate into OH and H with an energy barrier of 0.37 eV and the reaction is exothermic by 1.73 eV. Moreover, the OH group, perpendicular to the surface, can furtherly dissociate into H and O with a 0.57 eV energy barrier and the reaction is exothermic by 1.2 eV. The dissociation of H2O is highly exothermic and the dissociation barrier is significantly lower than the adsorption energy, indicating that H2O easily dissociates on the gamma-U(110) surface.