Structural, optoelectronic, magnetic, elastic, thermodynamic and thermoelectric properties of NaVSi half-Heusler alloys

Abstract

Structural, electronic, magnetic, mechanical, optical, thermodynamic, and transport properties of half-Heusler alloys are determined via the DFT method integrated into the Wien2k code. It was shown that the NaVSi compound crystallizes in the cubic structure, space group 216 (F3m) and was identified as a stable half-metal compound in the ferromagnetic state Y2. The calculation using the GGA-mBJ approximation resulted in a direct band gap energy of 1.17 eV in the spin-down states. The derived total magnetic moment is 2μ_B. The negative formation energy proved its stability against phase separation. Elastic constants and mechanical study indicated that the material was of a ductile nature and mechanically stable. Also, thermodynamic parameters of NaVSi were similarly explored in this investigation. In addition, the optical responses, such as dielectric function, optical conductivity, reflectivity, absorption coefficient, energy loss, and refractive index, were correlated and deeply discussed, highlighting the importance of the findings. Finally, utilizing Boltzmann's quasi-classical theory, thermoelectric properties of the material, including the Seebeck coefficient and electronic and lattice thermal conductivities, were probed. The ZT value was 0.19 at 300 K whereas it was 0.82 at 1000 K. The investigation demonstrated the potential of the material functionalization and highlighted its viability in optoelectronic applications namely photovoltaic and thermoelectric conversion.