Assessing structural, thermomechanical, and transport properties of FeNbZ (Z = P, As) half-Heuslers for thermoelectric devices via DFT calculations

The depletion of fossil fuels and environmental concerns drive the search for sustainable materials capable of converting waste heat into electricity. This study investigates the structural, thermomechanical, optical, and transport properties of FeNbZ (Z = P, As) half-Heusler compounds using density-functional theory and Boltzmann transport calculations. Mechanical stability is confirmed via Born criteria, with melting temperatures of 2629 K (FeNbP) and 2464 K (FeNbAs). Elastic indicators show FeNbP is ductile, while FeNbAs is brittle. Both compounds are semiconducting, with direct optical gaps of 0.69 eV (FeNbP) and 0.41 eV (FeNbAs), and optical peaks at 1.27/3.27 eV and 0.96/3.19 eV, respectively. Static dielectric constants are 6.84 and 8.46, with refractive index maxima of 3.24 at 2.17 eV. UV reflectivity reaches 95% (6.33–9.0 eV). Low minimum thermal conductivities (1.23 W/m•K and 1.15 W/m•K) highlight their thermoelectric potential. These findings position FeNbZ compounds as promising candidates for high-temperature thermoelectric and UV-protective applications.