First-principles study of the electronic and the optical properties of In6Se7 compound

The electronic and the optical properties of hexaindium heptaselenide In6Se7 have been reported using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in the Wien2k. In this approach, the alternative form of the generalized gradient approximation (GGA) proposed by Engel and Vosko (EV-GGA) was used for the exchange correlation potential. The calculated band structure shows a direct band gap (Z–Z). The contribution of different bands was analyzed from the total and the partial density of states curves. Moreover, the optical properties including the dielectric function, absorption spectrum, refractive index, extinction coefficient, reflectivity and energy-loss spectrum are all obtained and analyzed in details within the energy range up to 20 eV.