Wang, Lu; Shang, Jia-Xiang; Wang, Fu-He; Zhang, Yue and Chroneos, Alexander
Unexpected relationship between interlayer distances and surface/cleavage energies in γ -TiAl: density functional study.
Journal of Physics: Condensed Matter, 23(26) p. 265009.
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.
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