A First-principles Study Towards Understanding Behaviors Of Oxygen Adsorption Decorated Uranium Surfaces

Uranium?U?is the important nuclear fuel,which is used widely in n uclear industry.Due to its strong chemical reactivity,U surface can be easily corroded by oxidation in the atmospheric environment,so it is particularly important for us to store U and protect the U surface against corrosion.The experimental study shows that titanium?Ti?decoration and nitridation can develop good anticorrosion properties of U surface.Thus,the study of the interaction between the impurity?Ti or N?and oxygen?O?on U surface is very significance.In this paper,the effect of decorated U surfaces on the O behaviors on U surface has been investigated systematically using the first-principles approach.We mainly study the adsorption and dissociation of O atom and O₂ molecules on Ti-decorated U surface,the most stable adsorption site and adsorption energy are obtained by calculating the adsorption energy for O or O₂ in different adsorption sites on the surfaces.Using the Climbing Image Nudged Elastic Band?CI-NEB?method,we also study O diffusion on different surfaces.Besides,the O adsorption structures and adsorption energies in different adsorption sites on U surface for pre-adsorption N are also discussed,and O diffusion on surface and surface penetration into subsurface are calculated.The adsorption and diffusion of O atom on U surface are discussed when N atom is introduced into the octahedral interstitial site.It is found that O atoms tend to adsorb on the surface instead of absorbing in the subsurface.Ti atom on clean U surface can promote O atoms adsorption due to an attraction between Ti and O,it thereby impedes O diffusion which O atoms apart from the most favorable sites on U-Ti surface.Pre-adsorption N can suppress O adsorption on U surface adsorption,but it can promote O atom occupying interstitial site in surface.N also impedes O diffusion for O atoms jumping from the next hollow2 site.It can decrease the O diffusion barrier from surface into octahedral interstitial site in surface,but the O diffusion barrier is increased which O in subsurface diffuse to the surf ace.The N atom occupying the octahedral interstitial site can increase the O adsorption,the O atom prefers to locate the h2+site,but it has little effect on the O diffusion on surface.