Mechanical and thermodynamic properties of ?-TiAl using first-principles calculations

Temperature dependence of structural, mechanical, and thermodynamic properties of ?-TiAl is modeled using an extended quasi-harmonic approximation and first-principles calculations. In the first step, the volumes are estimated as a function of temperature following the quasi-harmonic approximation. The lattice parameters are further optimized at fixed volumes in the second step. Modeled mechanical properties (bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and hardness) agree with the experimentally reported mechanical properties. Similarly, the modeled thermodynamic properties (entropy, heat capacity at constant pressure, Gibbs free energy) are in good agreement with the thermodynamic properties reported from experiments and CALculation of PHAse Diagrams approaches. This study suggests that further optimization of the degree of freedom in the unit cell improves the model accuracy of properties estimated following the quasi-harmonic approximation.