  Detailed first principles calculations of the structural, electronic and
optical properties of two representatives of the chalcopyrite group of
compounds (LiInSe2 and LiInTe2) are reported in the present paper. Both
materials are shown to be the direct band gap semiconductors. Analysis of the
electronic properties showed that the degree of covalency increases if Se is
substituted by Te. Calculations of the optical properties of both crystals
allowed getting reliable approximation of the refractive index as a function of
the wavelength. All calculated results were compared with the available
experimental data; good agreement was demonstrated.
