Atomistic insights into interactions between oxygen and α –Zr ( 10 1 - 1 ) surface

Highlights: • O₂ molecule spontaneous dissociate on the Zr ($10\stackrel{-}{1}1$) surface. • Atom occupying the subsurface interstitial site is exothermic. • The energy barrier of O penetration to the subsurface is lower than 1.65 eV. • Zr ($10\stackrel{-}{1}1$) surface suffers fast oxidization kinetics. The oxidation corrosion is a crucial challenge for zirconium (Zr) alloys as cladding materials in fission power reactors. In the present study, a first-principles approach is employed for understanding behaviors of oxygen adsorbed on the Zr ($10\stackrel{-}{1}1$) surface. It is found that the Zr substrate is reactive to O species. Electrons in the 4d band of the metallic substrate tend to migrate to antibonding orbitals of the adsorbed O₂ molecule, leading to breaking the O-O bond and releasing energy. Several diffusion paths for an adsorbed O atom migrating to the subsurface interstitial site are proposed. It is found that the lowest diffusion barrier is only 0.08 eV. Therefore, it can be inferred that the Zr ($10\stackrel{-}{1}1$) surface suffers fast oxidation kinetics.