Comparison of O adsorption on Ni3Al (0Â 0Â 1), (0Â 1Â 1), and (1Â 1Â 1) surfaces through first-principles calculations

First-principles calculations were performed to study the properties of O adsorption on Ni3Al (0 0 1), (0 1 1), and (1 1 1) surfaces using the Cambridge serial total package (CASTEP) code. Stable adsorption sites are identified. The atomic and electronic structures and adsorption energies are predicted. The adsorption sites for O on the Ni3Al (0 0 1) surface are at the 2Ni-2Al fourfold hollow site, whereas O prefers to adsorb at the Ni-Al bridge site on (0 1 1) surface and 2Ni-Al threefold hollow site on (1 1 1) surface. It is found that O shows the strongest affinity for Al and the state of O is the most stabilized when O adsorbs on (0 0 1) surface, while the affinity of O for Al on (0 1 1) surface is weaker than (0 0 1) surface, and (1 1 1) surface is the weakest. The stronger O and Al affinity indicates more stable Al2O3 when oxidized. The experiment has shown that the oxidation resistance of single crystal superalloy in different orientations improves in the order of (1 1 1), (0 1 1), and (0 0 1) surface, suggesting that the oxidation in different crystallographic orientations may be related to the affinity of O for Al in the surface.