Neutron-scattering studies of arsenic sulphide glasses

High-resolution neutron-scattering measurements have been performed on bulk glasses of As2S3 and As2S3I1.65 at a spallation neutron source. For the case of As2S3, an isotopic-substitution experiment involving the S isotope has allowed some of the various pair correlations contributing to the second peak in the radial distribution function to be determined by the method of first differences. For the ternary glass, it has been confirmed that iodine bonds preferentially to As atoms, and that on average each As atom is coordinated to one iodine and two sulphur atoms in the first coordination shell.