The first-principles calculation based on time dependent - density functional theory (TDDFT) reveals the origin of the molecular electronic structure and its connection to the localized states of the g-GeS2(T-i). The band gaps computed for GenSm clusters representing the local structures and their correlation to the experimental band gaps of g-GexS100-x together with possible model of band-tail states of g-GeS2 have been discussed. According to the observed results we propose to consider the band-gap states of g-GexS100-x as superposition of electronic states of GenSm clusters. The type and concentration of these clusters are compositionally-dependent and influenced by technological conditions used for glass preparation
