First-principles insights into thermoelectric properties of topological nontrivial semimetal LiAuTe material

Abstract

Structural, electronic and thermoelectric properties of LiAuTe ternary compound are studied using density functional theory (DFT) and semi-classical Boltzmann transport theory. The cubic -phase (space group F3m) is predicted to be ground state structure with a significant energy difference compared to honeycomb structure (space group P63mmc). The mechanical and dynamical stability of the -phase is confirmed by calculating the elastic constants and phonon dispersion frequencies. At equilibrium lattice, with and without spin–orbit coupling, the LiAuTe compound band structure calculations show an s-p band inversion at Γ point, leading to a topological nontrivial semimetal phase. Thermoelectric parameters, such as Seebeck coefficient (S), electrical conductivity (σ), electronic (κ e ) and lattice (κ L ) thermal conductivities are computed. Electrons and holes relaxation times (τ) are also predicted. Hence, LiAuTe compound exhibits a low κ L value of 1.76 W mK−1 at room temperature which decreases with temperature increasing. At 900 K, κ L falls to 0.58 W mK−1 leading to a maximum ZT value of 0.52 at optimized n-doping concentration of 2.5 × 1020 cm−3. The present study reveals that LiAuTe compound is a suitable candidate for thermoelectric applications and will open new horizons for further researches on similar types of topological thermoelectric materials with better ZT.