First-principles study of structural, elastic, electronic and thermoelectric properties of NbRuX (X = P, As, Sb, Bi) half-heusler alloys

We explored the structural, electronic, mechanical and thermoelectric properties of NbRuX (X [Formula: see text] P, As, Sb, Bi) half-Heusler (HH) alloys utilizing density functional theory (DFT)-based quantum ESPRESSO (QE). We used the Perdew–Burke–Ernzerhof (PBE) functional within the generalized gradient approximation (GGA). Ground state energy calculations show the stability of the compounds, while elastic constant calculations confirm mechanical stability and their ductile nature across the series. The calculated lattice parameters for NbRuX (X [Formula: see text] P, As, Sb, Bi) are found to be 5.84, 5.97, 6.19 and 6.32 Å, respectively. Narrow indirect band gaps between 0.25 and 0.43[Formula: see text]eV are observed in the electronic band structure and density of states, indicating suitability for thermoelectric performance. Vibrational properties calculated using the thermo_pw code show the dynamic stability. Also, using the BoltzTraP code, we determined thermoelectric parameters. Thermoelectric analysis highlights high Seebeck coefficients and power factors, with NbRuBi showing the largest Seebeck coefficient of 640[Formula: see text][Formula: see text]V/K at 300[Formula: see text]K and NbRuP exhibiting the maximum power factor of [Formula: see text][Formula: see text]W/mK 2 at 300[Formula: see text]K. Here, NbRuSb achieves the highest electronic figure of merit (ZT [Formula: see text] 0.95) among all the HH alloys. Results suggest that NbRuX alloys are promising candidates for next-generation thermoelectric applications.