Density functional theory study on structural, mechanical, electronic, and phonon properties of CrAlB, MoAlB, WAlB, CrAlGa, MoAlGa, and WAlGa ternary compounds

In this study, we present the structural, mechanical, electronic, and optical properties of CrAlB, MoAlB, WAlB, CrAlGa, MoAlGa, and WAlGa compounds using first-principles density functional theory calculations. We assessed structural stability through heat of formation and found that most compounds have negative heat of formation indicating thermodynamic stability, except for MoAlGa and WAlGa. The elastic constants and moduli indicate that all CrAlB, MoAlB, WAlB, CrAlGa, MoAlGa, and WAlGa compounds are mechanically stable, exhibit elastic anisotropic behavior, relatively machinable, and mixed bonding characteristics with both ionic and covalent contributions. The MAlB (M = Cr, Mo, W) compounds display a brittle nature, whereas MAlGa exhibits ductile behavior. Analysis of Vickers hardness indicate that MAlB compounds are hard compared to MAlGa. The electronic band structures and density (DOS) of states indicate a clear metallic nature in both MAlGa and MAlB compounds. The electronic density difference plots indicate a spherical charge distribution with ionic bonding in MAlB and oblate charge distribution showing covalent bonding in MAlGa. Phonon dispersion analysis demonstrated dynamic stability in MAlB compounds, while MAlGa are dynamically unstable. We note that MAlB compounds are thermodynamically, mechanically, and dynamically stable, making them suitable for high-temperature structural applications such as aerospace and gas turbine engines. Graphical abstract