First principles investigation of electronic, optical and transport properties of α- and β-phase of arsenic telluride

Crystalline arsenic telluride exists in two stable phases. The monoclinic α-phase transforms to rhombohedral β-phase under high pressure. The electronic, optical and transport properties of the two phases has been investigated using full potential linear augmented plane wave (LAPW) + local orbitals (lo) scheme, in the framework of DFT with generalized gradient approximation (GGA). We present the energy bands, density of states and optical properties like the complex dielectric functions and absorption coefficients. From the dynamic dielectric constant, the structural anisotropy for the monoclinic α-phase is clearly observed, whereas the longitudinal and transverse components are almost identical for the β-phase. The optical absorption profiles clearly indicate that β-phase has possibility of greater multiple direct and indirect interband transitions in the infrared and visible regions compared to the α-phase. The rhomohedral phase which has the Bi2Te3 type structure has the possibility of thermoelectric properties, therefore transport properties like electrical and thermal conductivities, Seebeck and Hall coefficients etc. are also calculated. Good agreements are found with the available experimental results.

Research highlights► Electronic structure of monoclinic and rhombohedral phases of arsenic telluride have been investigated. ► The investigations use the full potential linearized plane wave (LAPW) and local orbitals (lo) scheme. ► The calculated optical properties shows birefringence for monoclinic phase whereas the rhombohedral phase shows good absorbance in optical region. ► Both phases of arsenic tellurides have high electrical and low thermal conductivities. ► The figure of merit of the two phases is ∼0.70, which is of the same order as of thermoelectric material Bi2Te3.