Unveiling the Pressure-Induced Properties and Ambient Thermoelectric Behaviour of Co₂YZ (Z =Si, Ge, Sn) Heusler Alloys

In this study, we present a comprehensive first-principles investigation of the pressure-dependent structural, elastic, thermodynamic, electronic, magnetic, and thermoelectric properties of Co 2 YZ Heusler alloys (Z = Si, Ge, Sn). Calculations were performed using both the plane-wave pseudopotential method (CASTEP) and the full-potential linearized augmented plane wave method (WIEN2k), enabling cross-validation of results. The elastic analysis confirms that Co 2 YSn remains mechanically stable up to 100 GPa, while Co 2 YGe and Co 2 YSi lose stability beyond 96 GPa and 83 GPa, respectively. Electronic band structure calculations at ambient pressure reveal a halfmetallic character in Co 2 YSi, whereas Co 2 YGe and Co 2 YSn exhibit metallic behaviour. The corresponding spin polarization at the Fermi level is 100% for Co 2 YSi, 95% for Co 2 YGe, and 86% for Co 2 YSn. Total magnetic moments align with the Slater-Pauling rule and decrease progressively under pressure. Thermoelectric properties computed via the BoltzTraP code highlight Co 2 YSi as a promising candidate for low-temperature waste heat recovery, with implications for energy efficiency and sustainable materials design.