First-Principles Insights into the Effect of Ta Substitution on Structural, Electronic, Thermodynamic, and Thermoelectric Properties of GaNiSb Half-Heusler Alloys

The structural, electronic, thermodynamic, and thermoelectric properties of GaNi_1–xTa_xSb alloys (x = 0.125–0.875) have been investigated using the FP-LAPW method within the framework of the generalized gradient approximation (GGA) and the modified Becke–Johnson (mBJ) potential for electronic properties. The results predict that these alloys exhibit ferromagnetic behavior. The calculated band structures and Density of states reveal an overlap between the valence and conduction bands, indicating a metallic character for all compositions considered. Furthermore, the quasi-harmonic Debye model has been employed to evaluate the thermodynamic properties of the alloys over the temperature range of 0–1800 K at ambient pressure (P = 0 GPa). The thermoelectric performance was assessed through electrical conductivity, thermal conductivity, Seebeck coefficient, and power factor. Among the studied compositions, GaNi_0.25Ta_0.75Sb and GaNi_0.75Ta_0.25Sb exhibit the highest power factors, suggesting their potential for high-temperature thermoelectric applications.