Crystal structure, electronic structure, and thermoelectric properties of β-Zn₄Sb₃ from first principles

Due to its complex and disordered structure, the relationship between crystal structure and electronic properties of β-Zn₄Sb₃ is still ambiguous. The effect of Zn vacancy and interstitial on the structure, bonding, electronic properties, and thermoelectric properties of β-Zn₄Sb₃ has been investigated by ab initio calculations in this work. It is demonstrated that the Zn-Zn bond distance increases significantly whereas the Zn-Sb bond distance increases slightly after fully optimization and relaxation. This abnormality is explained by exploring the bonding properties, which may attribute to the Zn deficiency and the disordered distributions of Zn in β-Zn₄Sb₃. Our calculations show that β-Zn₄Sb₃ is a p-type degenerated semiconductor with an indirect gap of 0.26 eV and a direct gap of 0.33 eV. An opposite effect on the electrical conductivity and Seebeck coefficient is found for both p-type and n-type dopants. Thus doping may not be exceptionally beneficial for improving the thermoelectric properties of β-Zn₄Sb₃.