  A topological insulator possesses a bulk energy gap splitting the lowest
empty band from the highest occupied electronic band. The electronic states at
the surface (or edge in two dimensions), on the other hand, of a topological
insulator are gapless and are protected by the time reversal symmetry. Such
systems are promising for variety of optoelectronic, superconducting,
thermoelectric and quantum computation related applications. We have studied
elastic, mechanical, electronic, optical properties, bonding character and the
electronic charge density distribution of ternary Bi2Te2Se topological
insulator. The compound under study is mechanically stable and elastically
anisotropic. The electronic band structure calculations reveal high degree of
anisotropy in the energy dispersion. Electronic effective mass is high in the
c-direction compared to that in the ab-plane. The optical constants show
moderate level of variation with respect to the polarization of the electric
field of the incident radiation. The optical spectra are consistent with the
electronic band structure and electronic density of states features. Both
electronic band structure and optical constants show clear indications of a
direct band gap of 0.610 eV for Bi2Te2Se. It is also found that Bi2Te2Se
possesses high refractive index at low photon energies in the infrared and
visible region. It has low reflectivity in the ultraviolet region. Bi2Te2Se
absorbs photons strongly in the ultraviolet energies. All these features make
Bi2Te2Se suitable for diverse class of optoelectronic device applications.
