First-principles investigation of phase stability and electronic structure of tetragonal (P4/m) Ga 3-x Al x Ti 2 (x = 0-3) compounds

We report a first-principles study of the phase stability and electronic structure of tetragonal (P4/m) Ga3-x Al x Ti2 (x = 0-3) compounds to investigate the conspicuous absence of Al3Ti2 in the Al-Ti phase diagram while isostructural Ga3Ti2 is stable in the Ga-Ti phase diagram. It is found that Ga3Ti2 is the most stable phase compared to its ternary derivatives (Ga3-x Al x)Ti2, with the stability of Al3Ti2 being the lowest. Furthermore, the equimolecular phase mixture of γ-TiAl and r-Al2Ti is found to be more stable than Al3Ti2. By analysing the total and partial density of states, the valence charge transfer and the valence charge density distributions, we substantiate our conclusions from the perspective of the electronic structure.