Thermoelectric and topological properties of half-Heusler compounds ZrIrX(As, Sb, Bi)

The strain dependent electronic structures, thermoelectric and topological properties of the half-Heusler compounds ZrIrX(X=As, Sb, Bi) are investigated by the first-principle calculations. At the equilibrium lattice constants, all the three compounds are trivial insulators and good thermoelectric materials with the Seebeck coefficient S and the power factor over relaxation time S2σ/τ as large as 1180 (μV/K) and 4.1 (1011Wm−1K−2s−1), respectively. The compressive strain enhances the band gap, while the tensile strain decreases the band gap. At some specific tensile strains, the compounds become Dirac-semimetals, with the s-type band Γ6 below p-type band Γ8, in the cubic phase. When we compress the a(b)-axis and elongate the c-axis of the compounds, they become the type-I Weyl semimetals. For ZrIrAs, the eight Weyl-Points (WPS) locate at (± Kx, 0, ± Kz), (0, ± Ky, ± Kz), Kx=Ky=0.008Å−1, Kz=0.043Å−1.