Physical properties of thermoelectric zinc antimonide using first-principles calculations

TL;DR

This study uses first-principles calculations to analyze the structural, electronic, elastic, and vibrational properties of ZnSb, aiming to understand and improve its thermoelectric performance by examining defects and phonon interactions.

Contribution

It provides a comprehensive first-principles analysis of ZnSb's properties, including defect stability and vibrational modes, offering insights into its thermoelectric behavior and potential improvements.

Findings

Zn and Sb atoms are electronically non-equivalent.

Low energy vibrational modes may reduce thermal conductivity.

Zinc vacancies are the most stable defects, explaining p-type conductivity.

Abstract

We report first principles calculations of the structural, electronic, elastic and vibrational properties of the semiconducting orthorhombic ZnSb compound. We study also the intrinsic point defects in order to eventually improve the thermoelectric properties of this already very promising thermoelectric material. Concerning the electronic properties, in addition to the band structure, we show that the Zn (Sb) crystallographically equivalent atoms are not exactly equivalent from the electronic point of view. Lattice dynamics, elastic and thermodynamic properties are found to be in good agreement with experiments and they confirm the non equivalency of the zinc and antimony atoms from the vibrational point of view. The calculated elastic properties show a relatively weak anisotropy and the hardest direction is the y direction. We observe the presence of low energy modes involving both Zn and Sb atoms at about 5-6 meV, similarly to what has been found in Zn4Sb3 and we suggest that the interactions of these modes with acoustic phonons could explain the relatively low thermal conductivity of ZnSb. Zinc vacancies are the most stable defects and this explains the intrinsic p-type conductivity of ZnSb.