Mechanism of oxygen adsorption on surfaces of γ-TiAl

► Surface stability of gamma-TiAl is in the order of (100), (111), (110), and (001). ► O could either adsorb or absorb in (100) surface with similar adsorption energies. ► The fcc-Al and hcp-Al sites are favorable sites if O adsorbs on (111) surface. ► O-Ti bond is stronger than O-Al bond, but a competition between them was observed. ► Oxidation resistance of gamma-TiAl could be improved by enhancing O-Al bonding.