Exploring the multifaceted properties of half-Heusler compounds XNiAs (X = Sc, Y): structural, electronic, optical, vibrational, mechanical, thermodynamic, and thermoelectric insights

Abstract The structural, electronic, optical, mechanical, vibrational, thermal, and thermoelectric properties of XNiAs half-Heusler compounds (X = Sc, Y) were studied in detail using a systematic first-principles density functional theory approach. First principle structural optimizations confirm the non-magnetic γ phase as the most energetically favorable configuration, yielding equilibrium lattice parameters of 5.84 Å for ScNiAs and 6.12 Å for YNiAs. Electron-structure calculations employing the mBJ-GGA functional yield indirect semiconductor-type band gaps of 0.39 eV and 0.45 eV for ScNiAs and YNiAs, respectively. Bulk modulus, calculated through the Born criteria, yields values close to 110 GPa for ScNiAs and 93 GPa for YNiAs, demonstrating a good ability to resist volume deformations. Phonon dispersion curves do not have any imaginary frequencies, indicating that the materials are dynamically stable. Using the quasi harmonic Debye model thermodynamics shows stable behavior until temperatures of 1000 K. Calculations of optical properties indicate strong absorption and reflectance in the UV range, suggesting that these materials may be useful for optoelectronic applications. Calculations of thermoelectric transport show very large Seebeck coefficients of ~ 229–236µVK − 1 at 300 K and suggest that the materials will have promising thermoelectric performance, as evidenced by room temperature ZT values approaching 0.76–0.78. These findings clearly indicate that XNiAs half Heusler compounds are suitable for application in both energy conversion and optoelectronic technologies.