Adsorption of oxygen on low-index surfaces of the TiAl{sub 3} alloy

• Published in: Journal of experimental and theoretical physics Vol. 123; no. 6
• Main Authors: Latyshev, A. M., Bakulin, A. V., Kulkova, S. E., Hu, Q. M., Yang, R.
• Format: Journal Article
• Language: English
• Published: United States 15.12.2016
• Subjects: ADSORPTION; ALUMINIUM COMPOUNDS; APPROXIMATIONS; BINARY ALLOY SYSTEMS; BINDING ENERGY; CHEMICAL BONDS; COMPARATIVE EVALUATIONS; CONCENTRATION RATIO; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CORRELATIONS; DIFFUSION BARRIERS; ELECTRONIC STRUCTURE; FERMI LEVEL; LAYERS; OXIDATION; OXYGEN; REDUCTION; SURFACES; TITANIUM COMPOUNDS; VALENCE; WAVE PROPAGATION
• ISSN: 1063-7761; 1090-6509
• DOI: 10.1134/S1063776116110133

Method of the projector augmented waves in the plane-wave basis within the generalized-gradient approximation for the exchange-correlation functional has been used to study oxygen adsorption on (001), (100), and (110) low-index surfaces of the TiAl{sub 3} alloy. It has been established that the sites that are most energetically preferred for the adsorption of oxygen are hollow (H) positions on the (001) surface and bridge (B) positions on the (110) and (100) surfaces. Structural and electronic factors that define their energy preference have been discussed. Changes in the atomic and electronic structure of subsurface layers that occur as the oxygen concentration increases to three monolayers have been analyzed. It has been shown that the formation of chemical bonds of oxygen with both components of the alloy leads to the appearance of states that are split-off from the bottoms of their valence bands, which is accompanied by the formation of a forbidden gap at the Fermi level and by a weakening of the Ti–Al metallic bonds in the alloy. On the Al-terminated (001) and (110) surfaces, the oxidation of aluminum dominates over that of titanium. On the whole, the binding energy of oxygen on the low-index surfaces with a mixed termination is higher than that at the aluminum-terminated surface. The calculation of the diffusion of oxygen in the TiAl{sub 3} alloy has shown that the lowest barriers correspond to the diffusion between tetrahedral positions in the (001) plane; the diffusion of oxygen in the [001] direction occurs through octahedral and tetrahedral positions. An increase in the concentration of aluminum in the alloy favors a reduction in the height of the energy barriers as compared to the corresponding barriers in the γ-TiAl alloy.