Iron based Efficient Room Temperature Thermoelectric Materials: A DFT Study on FeXSn (X = Nb, Ta) Half-Heusler Alloys

Abstract

Half-Heusler alloys FeXSn (X = Nb, Ta) with 17 valence electrons in the cubic F–43m phase are investigated using first-principles density functional theory. Structural optimization yields equilibrium lattice parameters of 6.0333 and 6.0221 ˚A for FeNbSn and FeTaSn, respectively. The calculated elastic constants (C11, C12, C44) satisfy the Born–Huang criteria, and phonon dispersion confirms their dynamical stability. Electronic band structure analysis reveals half-metallicity with 100% spin polarization at the Fermi level, showing a semiconducting spin-up channel and metallic spin-down channel. Ferromagnetic ordering is observed, primarily contributed by Fe atoms. Thermoelectric transport coefficients are obtained within both the constant relaxation time approximation (τ = 10−15 s) and the deformation potential framework. The lattice thermal conductivity (κL) is evaluated using the Slack model and ab initio molecular dynamics, providing consistent trends. Our results highlight that FeNbSn and FeTaSn combine structural robustness, half-metallicity, and promising thermoelectric performance, indicating their potential for spintronic devices and room-temperature thermoelectric applications.