Theoretical prediction of the structural, electronic, mechanical and thermodynamic properties of the binary α-As₂Te₃ and β-As₂Te₃

The structural, electronic, mechanical and thermodynamic properties of α- and β-As₂Te₃ are investigated by using the first-principles. The optimized lattice constants of α- and β-As₂Te₃ are in a good agreement with the available experimental data. The electronic structures suggest that both of α and β phases are semiconductor. Further calculations of elastic constants confirm that both of them are mechanically stable and the β phase is stiffer than α phase. Furthermore, the ratio values of B/G and hardness are also calculated. The results reveal that α phase is ductile while β phase is brittle, and the hardness value is 3.56 GPa and 7.44 GPa for α and β phase, respectively. In addition, the 3D directional dependences of the reciprocal of Young's modulus and bulk modulus for α and β phase are also obtained. The results show that α phase exhibits remarkable anisotropy. Finally, the Debye temperature and minimum thermal conductivity are obtained. - Highlights: • α-As₂Te₃ is an indirect band gap semiconductor, β-As₂Te₃ is a direct band gap semiconductor. • Both of α- and β-As₂Te₃ are mechanically stable. α phase is ductile while β phase is brittle. • The hardness value is 3.56 GPa and 7.44 GPa for α and β phase, respectively. • The α phase exhibits remarkable anisotropy.