Exploring the effect of pressure on the structural electronic and thermodynamic properties of CoHfGe half Heusler alloy using first principles calculation

This study utilizes density functional theory (DFT) and Boltzmann transport theory to comprehensively explore the pressure-dependent structural, magnetic, elastic, electrical, thermodynamic, and thermoelectric properties of the half Heusler compound CoHfGe within the pressure range of 0 to 25 GPa. With increasing pressure, both the unit cell volume and normalized lattice parameters decrease. The elastic constants calculated at zero pressure, along with their positive pressure dependence up to 25 GPa, confirm the stability of CoHfGe as per the Born criteria. Electronic band structure calculations indicate the half-metallic nature of CoHfGe, with a band gap of 0.87 eV at zero pressure. Using the Voigt-Reuss-Hill (VRH) averaging scheme, we evaluate the bulk modulus (B), shear modulus (G), Young's modulus (E), Pugh ratio (B/G), Poisson's ratio (σ), and anisotropy factor (A) under pressure. The linear increase in the bulk modulus with pressure suggests a corresponding enhancement in material hardness. Thermal properties, such as the thermal expansion coefficient, Debye temperature, Grüneisen parameter, heat capacity, and lattice thermal conductivity are determined using the Debye model. Additionally, the study investigates the pressure dependence of thermoelectric properties, revealing potential for pressure-induced optimization. This comprehensive analysis underscores the tunability of CoHfGe's spintronic and transport properties via external pressure, highlighting its promise for a range of applications in both industrial and academic research. These findings pave the way for future studies aimed at exploring the material's potential across various scientific and technological fields.