Thermoelectric properties of tetragonal half-Heusler compounds, TiXSb (X = Ge, Si): A probe from Density Functional Theory (DFT)

Abstract

We have presented the electronic and thermoelectric properties of d sup(2)/d sup(o) type Heusler compounds TiXSb (X = Ge, Si) using Full Potential Linearized Augmented Plane Wave method (FP-LAPW), based on Density Functional Theory (DFT). For electron exchange, we have considered the most common Generalized Gradient Approximation (GGA), exchange potential. The electronic structure of both TiGeSb and TiSiSb showed overlapping between the valance and the conduction band, indicating their metallic nature. The transport coefficients were calculated by a post DFT treatment which involves the semi-classical Boltzmann Theory as implemented in the code BoltzTraP. The thermoelectric parameters are calculated along perpendicular and parallel directions with respect to chemical potential (mu) and temperature. Furthermore, we have also considered the phononic contribution to thermal conductivity (Kappa sub(p)) for better understanding of the materials thermodynamics and efficiency (ZT). The calculated ZT values showed TiSiSb as potential thermoelectric candidate at room temperature and under normal conditions, whereas TiGeSb had poor thermoelectric properties.