Advanced materials for next-generation devices: insights into the structural, optical, and thermoelectric properties of Hf2Pd2AlBi and Hf2Pd2AlSb alloys

Abstract

In this work, we systematically investigated the structural, optoelectronic, and thermoelectric properties of the double half-Heusler (DHH) compounds Hf₂Pd₂AlBi and Hf₂Pd₂AlSb. The study was conducted using density functional theory (DFT) within the framework of the generalized gradient approximation (GGA-PBE), complemented by the modified Becke–Johnson potential (mBJ-GGA) to enhance the accuracy of electronic property predictions. Our results indicate that both Hf₂Pd₂AlBi and Hf₂Pd₂AlSb are thermodynamically most stable in their non-magnetic (NM) phase. Electronic structure analysis reveals semiconducting behavior, with direct band gaps at the Γ point of 0.308 eV for Hf₂Pd₂AlBi and 0.405 eV for Hf₂Pd₂AlSb. A comprehensive evaluation of optical properties was performed, including the complex dielectric function, optical conductivity, refractive index, absorption coefficient, and reflectivity. Additionally, melting temperatures and elastic constants were estimated to assess thermal and mechanical stability. Thermoelectric performance evaluated through Boltzmann transport theory, showed high Seebeck coefficients and factors of merit (ZT), underscoring the potential of both compounds for thermoelectric applications.