Comparative Study of Optoelectronic and Thermoelectric Performance of Quaternary Heusler LiHfRhZ (Z = Si, Ge) Alloys for Energy Harvesting Applications

In the present study, the electronic structure, phonon dynamics, thermodynamics, elastic, optical and thermoelectric properties of quaternary Heusler LiHfRhZ (Z = Si, Ge) are explored using the full potential linearized augmented plane wave method within the framework of density functional theory. The indirect bandgap semiconductor nature of both alloys has been established by the band structure and density of states calculations. Further, the calculations of formation energy, phonon dispersion, elastic constants, and thermodynamic properties confirmed the structural, dynamical, mechanical and thermodynamic stability of the materials along with their anisotropic nature. Investigation of optical properties shows higher dielectric function values in the low‐energy range (≈2 eV), followed by a decline with increasing photon energy. The alloys demonstrate strong reflectivity in the ultraviolet region, suggesting their potential as ultraviolet coating materials and exhibit optical conductivity in the visible region. Both the studied alloys exhibit an increasing trend in power factor, indicating a strong potential for high‐temperature thermoelectric performance. Notably, LiHfRhGe achieves a maximum ZT value of 0.73 at 1000 K, which is comparatively higher and more stable than those of other QH alloys. Given the limited research on these alloys, this study can serve as vital foundation for further theoretical and experimental research on this field.