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<p>In the framework of density functional theory (DFT) in conjunction with Boltzmann transport formalism, we present a comprehensive investigation of the structural stability, electronic structure, vibrational behavior, and thermoelectric performance of nine Ni-based half-Heusler alloys: NiScP, NiScAs, NiScSb, NiTiSi, NiTiGe, NiTiSn, NiVAl, NiVGa, and NiVIn. All compounds crystallize in the cubic F-43m (216) space group and exhibit non-magnetic semiconducting characteristics. Mechanical stability is confirmed through elastic constant calculations, which is further corroborated by phonon dispersion curves and the Born–Huang stability criteria. Initial electronic structure results reveal indirect semiconducting bandgaps, refined accurately using the HSE06 hybrid functional to ensure reliable transport predictions. A detailed analysis of the vibrational and mechanical properties including bulk, shear, and Young’s moduli, longitudinal and transverse sound velocity (with directional components), and Debye temperature demonstrates the mechanical robustness of these alloys at elevated temperatures. Thermoelectric coefficients including the Seebeck coefficient, electrical conductivity, and the electronic contribution to thermal conductivity are obtained by solving the Boltzmann transport equation under the constant relaxation time approximation (CRTA) using BoltzTraP. The figure of merit (<i>ZT</i>) is evaluated as a function of temperature, incorporating the lattice thermal conductivity, and the optimal carrier concentrations are identified for both <i>n</i>-type and <i>p</i>-type conduction. Several alloys exhibit notable high-temperature thermoelectric performance: NiScP achieves <i>ZT</i> values of 0.88 (<i>n</i>-type) and 0.84 (<i>p</i>-type) at 900 K; NiTiGe reaches <i>ZT</i> = 0.79 (<i>n</i>-type) at 900 K; NiTiSn attains <i>ZT</i> = 0.82 (<i>p</i>-type) at 850 K; and NiVGa shows <i>ZT</i> values of 0.85 (<i>n</i>-type) and 0.84 (<i>p</i>-type) at 900 K. These enhanced thermoelectric responses arise primarily from the favorable bandgaps and density-of-states features near the Fermi level. Overall, our findings establish these Ni-based half-Heusler alloys as promising candidates for high-temperature thermoelectric energy conversion, supported by their mechanical stability, optimized electronic structure, and theoretically predicted thermal properties.</p>

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High-Temperature Nickel-Based Half-Heusler Thermoelectrics: A Comprehensive Ab-Initio Exploration for Advanced Energy Conversion

  • 期刊论文

  • 发表日期：

    2026年6月22日

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  • Enamullah Khan

摘要

In the framework of density functional theory (DFT) in conjunction with Boltzmann transport formalism, we present a comprehensive investigation of the structural stability, electronic structure, vibrational behavior, and thermoelectric performance of nine Ni-based half-Heusler alloys: NiScP, NiScAs, NiScSb, NiTiSi, NiTiGe, NiTiSn, NiVAl, NiVGa, and NiVIn. All compounds crystallize in the cubic F-43m (216) space group and exhibit non-magnetic semiconducting characteristics. Mechanical stability is confirmed through elastic constant calculations, which is further corroborated by phonon dispersion curves and the Born–Huang stability criteria. Initial electronic structure results reveal indirect semiconducting bandgaps, refined accurately using the HSE06 hybrid functional to ensure reliable transport predictions. A detailed analysis of the vibrational and mechanical properties including bulk, shear, and Young’s moduli, longitudinal and transverse sound velocity (with directional components), and Debye temperature demonstrates the mechanical robustness of these alloys at elevated temperatures. Thermoelectric coefficients including the Seebeck coefficient, electrical conductivity, and the electronic contribution to thermal conductivity are obtained by solving the Boltzmann transport equation under the constant relaxation time approximation (CRTA) using BoltzTraP. The figure of merit (ZT) is evaluated as a function of temperature, incorporating the lattice thermal conductivity, and the optimal carrier concentrations are identified for both n-type and p-type conduction. Several alloys exhibit notable high-temperature thermoelectric performance: NiScP achieves ZT values of 0.88 (n-type) and 0.84 (p-type) at 900 K; NiTiGe reaches ZT = 0.79 (n-type) at 900 K; NiTiSn attains ZT = 0.82 (p-type) at 850 K; and NiVGa shows ZT values of 0.85 (n-type) and 0.84 (p-type) at 900 K. These enhanced thermoelectric responses arise primarily from the favorable bandgaps and density-of-states features near the Fermi level. Overall, our findings establish these Ni-based half-Heusler alloys as promising candidates for high-temperature thermoelectric energy conversion, supported by their mechanical stability, optimized electronic structure, and theoretically predicted thermal properties.