Computational analysis on novel half Heusler alloys XPdSi ( X = Ti, Zr, H f ) for waste heat recycling process

We have investigated the electronic, thermodynamic, mechanical, and thermoelectric properties of ternary Heusler alloys XPdSi ( X = Ti, Zr, H f ) based on 18 valence electron count rule. The combined full potential linearized augmented plane wave method and generalized gradient approximation have used to optimize the structure and band dispersion calculation. The electronic calculation reveals the indirect semiconducting band gap of the chosen half Heusler alloys. Investigations were also conducted into the thermodynamic parameters, such as Debye temperature, heat capacity, entropy, vibrational energy, and internal energy. Evidently, the high -temperature heat capacity complies with the traditional Dulong-Petit law while the low -temperature heat capacity adheres to the Debye heat capacity hypothesis. Moreover, the calculated ratio B / G , Cauchy pressure and Poisson's ratio signify the ductile behavior of the studied alloys. The phonon dispersion studies confirm the dynamical stability of the considered Heusler alloys as the phonon spectrum shows the positive frequencies. The semi classical Boltzmann transport theory with constant relaxation time approximation was used to calculate the thermoelectric characteristics. XPdSi ( X = Ti, Zr, H f ) has a maximum Seebeck coefficient value of 127.3 mu V/K, 116.8 mu V/K and 108.9 mu V/K, respectively, at temperatures of 1200 K. The corresponding figures of merit values are 0.37, 0.31, and 0.28 at same temperature, it shows that these alloys are the potential candidates for waste heat recovery application.