First principles study of H2O adsorption on U2Ti (1 1 0) surface

Abstract

U-Ti alloy is a kind of metallic nuclear fuel that has been of interest to the nuclear power industry. Nuclear fuel is exposed to an aggressive physical, chemical and radiative environment, and may suffer corrosion damage caused by irradiation or chemicals like water vapour. Surface adsorption is the very start of the corrosion process. In this work, basing on the density functional theory (DFT) corrected for on-site Coulomb interactions (DFT + U), we investigate the adsorption behavior of H2O on U2Ti surface. U2Ti (1 1 0) surface is predicted to be the most stable one using DFT + U calculations. Eight possible sites are chosen to conveniently demonstrate the chemical circumstance on the (1 1 0) surface. Our study shows that the adsorption of H2O on U2Ti (1 1 0) surface is a mixed adsorption involving both physisorption and chemisorption. Physisorption can be observed on all these sites with an equilibrium distance, while chemisorption can only occur on some sites, mostly represented as dissociative adsorption. Density of states and deformation charge density are also calculated to examine the charge transfer between surface atoms as well as atoms in the bulk. A climbing image nudged elastic band (CI-NEB) method is used to determine the energy barriers for H2O migrating from the equilibrium position of physisorption to the states of dissociative adsorption. Bader charge analysis was performed to determine the numerical values of charge on each adsorbed atom.