Effect of Pressure on Elastic Constants and Related Properties of Rare-Earth Intermetallic Compound TbNiAl

The Lennard-Jones potential approach is used to investigate the effect of pressure on the ultrasonic and elastic properties of the rare-earth ternary TbNiAl intermetallic compound. The second- and third-order elastic constants of TbNiAl are considered using the potential model. The pressure-dependent higher-order elastic constants are studied, and it is observed that the elastic constants of the TbNiAl compound increased monotonously with pressure. The hexagonal TbNiAl compound is mechanically stable up to the pressure 20 GPa according to the Born elastic stability criteria. The Voigt–Reuss–Hill approach is used to compute such elastic parameters as Young’s modulus, bulk modulus, Poisson’s ratio, and shear modulus in the pressure range 0–45 GPa. Hardness, melting temperature, and anisotropy are also determined for the intermetallic TbNiAl compound. The pressure-dependent velocities and attenuation of ultrasonic waves in this ternary compound are evaluated. The computation results are also satisfactory in estimating the Debye temperature and thermal conductivity K_min under different pressure. It is observed that TbNiAl has a significant anisotropy at zero pressure, which becomes stronger as the pressure increased. This ternary compound behaves as its purest form at higher pressure and is more ductile, which is demonstrated by the minimum attenuation.