The structure of vitreous boron sulphide

Neutron diffraction and inelastic scattering experiments have been performed on high purity vitreous B2S3 to investigate whether the two superstructural units, three-membered rings (borsulphol groups) and pairs of edge-sharing BS3 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 BS3 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 Å, which corresponds to the B–(2)O distance at ∼3.6 Å within a boroxol group for vitreous B2O3, 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 BS3 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.