Adsorption and diffusion of oxygen on γ-TiAl(001) and (100) surfaces

[Display omitted] •Oxygen prefers the Ti-rich environments on TiAl(001) and (100) surfaces.•O diffusion within surface layers is more preferable than that into the bulk.•Energy barrier increases considerably if O atom diffuses from the Ti-rich sites.•High barrier of 3eV is found for O diffusion into TiAl(001)Ti subsurface layer.•Optimum diffusion path into (100) subsurface is through tetrahedral sites. Adsorption and diffusion of oxygen atom on both (001) and (100) surfaces of γ-TiAl are investigated by using the plane-wave pseudopotential method within the generalized gradient approximation for the exchange correlation functional. The structural and electronic properties of pure surfaces and with adsorbed oxygen are studied. We find that the bridge position is preferable for O adsorption on the Al-terminated (001) surface and the hollow one for the Ti-terminated (001) as well as on (100) surface. It was shown that the interaction between O and Ti-terminated TiAl(001) surface is much stronger than that with other considered surfaces. The energy barriers of oxygen diffusion between different sites on surface as well as in subsurface region are calculated. Oxygen prefers the Ti-rich environments on the surface and in subsurface layers. The values of barriers depend substantially on the local environments of oxygen atom and increase when oxygen hops from Ti-rich site. Besides the diffusion of oxygen crossing Al layer is easier than that crossing Ti layer. The obtained results provide a deep insight on the O interaction with γ-TiAl low-index surfaces.