Résumé: 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 (F %43m) 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 2mB. 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.

Résumé: Employing first-principles calculations, the structural, mechanical, electromagnetic characteristics of FeTiCrAl(1-x)Six alloys are investigated. Structural and mechanical characteristics are computed with GGA approach, while mBJ and GGA + U approaches are used to calculate the electromagnetic characteristics. Mechanical stability is demonstrated by every thermodynamically stable material. Furthermore, the electronic data reveal that FeTiCrAl is a semiconductor, whereas FeTiCrAl(1−x)Six (0≤x≤01) alloys are half-metallic ferromagnets. Apart from the minority states of FeTiCrAl, all the examined materials show direct band gap. Exploiting the mean field approximation (MFA), this class of systems is revealed to have a high Curie temperature, indicating its suitability for spin injection. The total magnetic moment of the parent compounds has an integer value, following the Slater-Pauling rule. Additionally, the thermodynamic stability of the parent compounds and their doped alloys was investigated using a regular-solution model. Using the quasi-harmonic Debye model, various thermodynamic parameters were studied at different temperatures.