Comparison of O adsorption on Ni3Al (001), (011), and (111) 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 11), (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. (C) 2012 Elsevier B.V. All rights reserved.