Thermodynamic Calculation on the Formation of Titanium Hydride.

A modified Miedema model, using interrelationship among the basic properties of elements Ti and H, is employed to calculate the standard enthalpy of formation of titanium hydride TiH_x (1 ≤ x ≤ 2). Based on Debye theories of solid thermal capacity, the vibrational entropy, as well as electronic entropy, is acquired by quantum mechanics and statistic thermodynamics methods, and a new approach is presented to calculate the standard entropy of formation of TiH₂. The values of standard enthalpy of formation of TiH_x decrease linearly with increase of x. The calculated results of standard enthalpy, entropy, and free energy of formation of TiH₂ at 298.16 K are −142.39 kJ/mol, −143.0 J/(mol·K) and −99.75 kJ/mol, respectively, which is consistent with the previously-reported data obtained by either experimental or theoretical calculation methods. The results show that the thermodynamic model for titanium hydride is reasonable. [ABSTRACT FROM AUTHOR]