Predictive study of the new double Half-Heusler compounds Hf 2 FeNiSb 2 , Nb 2 Co 2 GaSb and ScNbCo 2 Sb 2 , promising candidates for thermoelectric applications

This study investigates the structural, electronic, and thermoelectric properties of three Double Half-Heusler (DHH) compounds: Hf 2 FeNiSb 2 , Nb 2 Co 2 GaSb, and ScNbCo 2 Sb 2 , using the full-potential linearized augmented plane wave (FP-LAPW) approach based on density functional theory (DFT) and implemented in the Wien2k software. In this analysis, we have used the GGA-PBE approximation for treating the exchange-correlation potential and the TB-mBJ-GGA approximation to enhance the energy band gaps, aiming to align them more closely with the experimental values. According to our research results, we can say that these compounds exhibit stability in the non-magnetic phase and exhibit no total magnetic moment. The determined band gap values for these compounds indicate their semiconducting nature, with indirect gap values of 0.42, 0.55, and 0.67 eV for Hf 2 FeNiSb 2 , Nb 2 Co 2 GaSb, and ScNbCo2Sb 2 , respectively. These values are determined using the TB-mBJ-GGA approximation, which is recommended for improving energy gap values and approaching experimental values. Moreover, these compounds demonstrate remarkable figure of merit (ZT) values approaching unity, indicating their potential as promising materials for thermoelectric applications. Specifically, the thermoelectric properties of Hf 2 FeNiSb 2 and ScNbCo 2 Sb 2 improve at low temperatures (0–100K), while Nb 2 Co 2 GaSb displays the best thermoelectric efficiency in the temperature range of 500–800K.