Abstract
Indium thiospinel compound with normal spinel structure HgIn2S4 single crystal was synthesized by the Bridgman method, and far-infrared reflection and transmission spectra were measured in the wavelength region from 20 to 1000 cm-1. The dispersion parameters are calculated by dispersion analysis using classical oscillators. The strength of the four kinds of short-range force constant is calculated using the dynamical matrices proposed by Bruesch et al., and the effective charges for each ion are obtained under several assumptions.