Electronic Structure and Thermoelectric Performance of Narrow‐Gap GdNiSb Half Heusler Compound: Density Functional Calculations

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The rare earth‐based half Heusler GdNiSb compound is investigated theoretically for electronic and thermoelectric (TE) performance. The most efficient method to treat the rare earth metals, Coulomb‐corrected local spin density approximation (LSDA + U), is used. The calculated total density of states (DOS) of GdNiSb shows that the maximum contribution near Fermi energy (EF) is due to the spin‐up/down Ni‐3d and spin‐down Gd‐4f states. A narrow energy gap of 0.279 eV is opened which is consistent with other reported values. TE properties are investigated using classical transport theory. The total Seebeck coefficient (S) increases linearly with temperature and attains a maximum value of 80 μV K−1 at 800 K. The S value of 60 μV K−1 at 380 K is in good agreement with the experimental value, 58 μV K−1, at the same temperature. The maximum value of the power factor (P) is as high as 825 × 109 W m−1 K−2 s−1 at 650 K in the spin‐down channel. The TE figure of merit (ZT) reaches the maximum value of ≈0.475 at 800 K in the spin‐down configuration. All the values of the TE parameters of GdNiSb indicate a good candidate for TE applications.