title: Unexpected relationship between interlayer distances and surface/cleavage energies in γ-TiAl: density functional study.
abstract: Density functional calculations were performed to study the γ-TiAl (001), (100), (110) and (111) surfaces. The (100) surface is the most stable under Ti-rich conditions, while the Al-termination (110) surface becomes the most stable with the increase of Al chemical potential. We calculate that in γ-TiAl intermetallic compound the larger the interlayer distance, the larger the surface energy and cleavage energy. This is different from the situation in a pure metal. This phenomenon can be explained by the analysis of the bonding characteristics in γ-TiAl. In particular there are both metallic and covalent bonds in γ-TiAl, and the strongest covalent bonds mainly focus on the center of three Ti-Al-Ti atoms. It is the covalent bonds that affect greatly the cleavage energy, the surface energy and the surface stability.
authors.affiliation: School of Materials Science and Engineering, Beihang University, Beijing 100191, People's Republic of China.
authors.forename: Lu
authors.initials: L
authors.lastname: Wang
authors.forename: Jia-Xiang
authors.initials: JX
authors.lastname: Shang
authors.forename: Fu-He
authors.initials: FH
authors.lastname: Wang
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhang
authors.forename: Alexander
authors.initials: A
authors.lastname: Chroneos