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 S-2 sigma/tau as large as 1180 (mu V/K) and 4.1 (10(11)Wm(-1)K(-2)s(-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 Gamma(6) below p-type band Gamma(8), 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 (+/- K-x, 0, +/- K-z), (0, +/- K-y, +/- K-z), K-x = K-y = 0.008 angstrom(-1), K-z = 0.043 angstrom(-1). (C) 2018 Elsevier B.V. All rights reserved.