First-principles investigation of the novel structure,elastic and thermodynamic properties of IrAl3 coating

IrAl₃ coating is a promising advanced functional material. However, the crystal structure and relevant properties of IrAl₃ remain controversy. Here, we apply the first-principles calculations to investigate the crystal structure, elastic and thermodynamic properties of IrAl₃. The phonon dispersion curves and phonon density of states of IrAl₃ are calculated. We find that the reported hexagonal structure (P63/mmc) is dynamically instable. However, three new phases: tetragonal (P4/mbm) and cubic (Pm-3n and Pm-3?m) structures are predicted. In particular, IrTi₃-type structure is a derivative cubic structure because Al atom occurs migration from (0, 0.50, 0.50) site to (0, 0.25, 0.50) site. IrTi₃-type derivative cubic structure shows high shear deformation resistance and high elastic stiffness in comparison to other three structures. The strong shear deformation resistance and high elastic stiffness are attributed to the symmetrical Ir–Al bond. However, AuCu₃-type structure shows the high Debye temperature and low heat capacity in comparison to other structures.