The structure of vitreous boron sulphide

Abstract Neutron diffraction and inelastic scattering experiments have been performed on high purity vitreous B 2 S 3 to investigate whether the two superstructural units, three-membered rings (borsulphol groups) and pairs of edge-sharing BS 3 triangles that are observed in the crystalline structure are also observed in the glass phase. The correlation function, T ( r ), indicates that the structural units in the glass are planar BS 3 triangles, with a B–S bond length very similar to the value found in the crystal. There is also a well-defined peak in T ( r ) at ∼4.6 A, which corresponds to the B–(2)O distance at ∼3.6 A within a boroxol group for vitreous B 2 O 3 , thus indicating the presence of a large fraction of borsulphol groups. The conclusion of an earlier Raman spectroscopy study, concerning the occurrence in the glass of significant numbers of edge-sharing BS 3 triangles, is not supported. Most peak positions in the effective vibrational density of states derived from inelastic neutron scattering are in broad agreement with those found from Raman and infra-red studies but the relative intensities are very different. In addition, new intense features are reported.