Electronic structure, optical and thermoelectric properties of half-Heusler ZrIrX(X = As, Sb, Bi): a first principles study

The electronic structure, optical and thermoelectric properties of half-Heusler ZrIrX (X= As, Sb, Bi) compounds were investigated under pressure by using the modified Becke and Johnson exchange potential. The band gaps of ZrIrAs and ZrIrBi increase from tensile strain (epsilon = 5%) to compressive strain (epsilon = -5%), and at about e = -4% they changed from indirect to direct band gaps. Their absorption efficiencies increase from compressive to tensile strain in the low energy (<= 2.8 eV). For p-type doped compounds, the Seebeck coefficients and the power factors increase from tensile to compressive strain. While the the Seebeck coefficients and the power factors of n-type compounds, first increase and then decrease from tensile to compressive strain, reaching the largest values at the critical strain (direct-indirect transition). ZrIrSb is an indirect band gap insulator, but it translates to direct band gap insulator when the tensile strain epsilon >= 2%.