Origin of the antioxidation mechanism of RuAl(1 1 0) surface from first-principles calculations

•The antioxidation mechanism of RuAl film is studied by first-principles calculation.•The influence of alloying elements on the oxidation resistance of RuAl (1 1 1) surface is studied.•Cr element improves the oxidation resistance of RuAl(1 1 1) surface.•Oxygen prefers to occupy the Ru-bridge site in comparison to other sites.•The calculated bond strength of Cr-O bond is stronger than that of Al-O bond. We apply the first-principles calculations to investigate the influence of Cr and Y on the oxidation resistance of RuAl(1 1 0) surface. Four possible oxygen adsorption sites: Al-top, Ru-top, Ru-bridge and Al-bridge are considered. It is found that the capacity of oxidation resistance of Ru is stronger than that of Al. Oxygen atom is adsorbed on the Ru-bridge site because of the strong charge interaction between Ru and the O. Importantly, the calculated adsorption energy of Cr-doped RuAl(1 1 0) surface is −0.350 eV, which is smaller than that of Ru-bridge site. The calculated result indicates that Cr-dopant can improve the oxidation resistance of RuAl(1 1 0) surface. The reason is that Cr-dopant improves the localized hybridization between Cr atom and the O atom, and weakens the charge interaction of Ru-O atoms and Al-O atoms. Therefore, we predict that Cr is a beneficial element to improve the oxidation resistance of RuAl thermal barrier coating.