The mid-infrared nonlinear optical (NLO) crystal, LiInS2, was successfully grown by the modified Bridgman method with an accelerated crucible rotation technique (ACRT). Spectral properties such as UV-vis-NIR and the mid-IR transmittance of LiInS2 have been investigated. First-principles study of the electronic structure and optical properties (dielectric function and refractive index) of LiInS2 has been performed by density function theory. The band structure shows that LiInS2 has a direct band gap of 3.21 eV. The calculated total and partial density of states indicate that the S-3p states mainly form the upper VBs, while the lower VBs are derived from the In-4d and S-3s states. The CBs are created by the S-3p, In-5s and In-5p states. The deep VBs lying at -43.2 eV originate mostly from Li-1s states. The charge density contours indicate that the bonds between the In and S atoms are covalent and that those between the Li and S atoms are ionic. This characteristic of the chemical bonding in LiInS2 also indicated from the Mulliken population analysis. (C) 2012 Elsevier B.V. All rights reserved.