Effects of irradiation defects on the adsorption of oxygen on 3C-SiC low index surfaces

Abstract

Silicon carbide (SiC) is widely regarded as a potential accident tolerant fuel cladding material for the next generation nuclear power system. Oxidation is the leading cause of failure of SiC in a high temperature environment. Adsorption of oxygen on SiC surface is the first stage of SiC oxidation. Effects of irradiation defects, such as vacancy and antisite atom, on the adsorption of oxygen on 3C-SiC low index surfaces are investigated by first principles calculation method. The results show that the oxygen molecule tends to dissociate spontaneously into two O atoms when adsorbed on the low index surfaces. The adsorption stability of oxygen molecule on the Si-terminated surface is higher than that on the C-terminated surface. As a whole, irradiation defects decrease the stability of oxygen adsorption on C-(100) and Si-(100) surfaces but increase the stability of oxygen adsorption on (110), (111), and (1¯1¯1¯) surfaces. Except for (110) surface, new covalent bonds as the precursors of oxides are formed on the SiC surfaces due to the irradiation defects, which changed the oxide species of other surfaces during the initial oxidation. Bader charge analysis and the local density of state results show that charge transfer plays a crucial role in the adsorption process.