Vibrational studies of the oxysulphide (LaO) 4 GaS 4.5

Far-infrared and Raman spectra of the oxysulphide (LaO)4GaS4.5 single crystal were measured and analysed. The interpretation of the observed spectra is based on the existence of (S-S)2− disulphur groups which are responsible for the high-frequency features. Most of the frequencies are assigned in terms of internal and external vibrations of tetrahedral La4O groups, GaS4 units and (S-S)2− disulphur groups. Spectroscopy measurements are in good agreement with the recent structure determination.