Physical properties of Thallium-Tellurium based thermoelectric compounds using first-principles simulations

TL;DR

This study uses first-principles simulations to analyze the thermodynamic, electronic, and elastic properties of Tl5Te3, BiTl9Te6, and SbTl9Te6 compounds, revealing their potential for thermoelectric applications.

Contribution

It provides detailed computational insights into the physical properties of Tl-Te based compounds, including electronic structure and elastic behavior, with implications for thermoelectric performance.

Findings

Optimized lattice constants match experimental data.

BiTl9Te6 and SbTl9Te6 have indirect band gaps of 0.256 eV and 0.374 eV.

Spin-orbit coupling significantly affects electronic structure.

Abstract

We present a study of the thermodynamic and physical properties of Tl5Te3, BiTl9Te6 and SbTl9Te6 compounds by means of density functional theory based calculations. The optimized lattice constants of the compounds are in good agreement with the experimental data. The electronic density of states and band structures are calculated to understand the bonding mechanism in the three compounds. The indirect band gap of BiTl9Te6 and SbTl9Te6 compounds are found to be equal to 0.256 eV and 0.374 eV, respectively. The spin-orbit coupling has important effects on the electronic structure of the two semiconducting compounds and should therefore be included for a good numerical description of these materials. The elastic constants of the three compounds have been calculated, and the bulk modulus, shear modulus, and young's modulus have been determined. The change from ductile to brittle behavior after Sb or Bi alloying is related to the change of the electronic properties. Finally, the Debye temperature, longitudinal, transverse and average sound velocities have been obtained.