First-principles study of water reacting with the (110) surface of uranium mononitride

The adsorption and dissociation behaviors of water on the UN (110) surface have been investigated by using DFT + U method in combination with ab initio atomistic thermodynamic simulations. The most stable adsorption site for H, O, and OH adsorption is the uranium bridge site. For a water monomer, the adsorption energies are -0.90, -3.23, and -4.46 eV for the most stable molecular, partially dissociative, and completely dissociative adsorption, respectively. The dissociation of water from H2O to OH and H has a very small energy barrier, while from OH to O and H has a high energy barrier of 1.63 eV. The coverage dependence for molecular adsorption is not obvious, while for partially dissociative and completely dissociative adsorption, the coverage dependence is quite obvious. Besides, we have investigated the adsorption of water under different temperature and pressure conditions by using the "ab initio atomistic thermodynamic" method. (C) 2017 Elsevier B.V. All rights reserved.