X-ray analysis of the structure of Ge–S–Ag glasses

Abstract

Glasses of the Ge 3−2 x Ag 2 x S 3 system were prepared in the composition range from x=0.6 to x=1. X-ray scattering curves are characterised by a first scattering peak (FSP) located at s ≈ 2 Å −1. For x=0.6 the radial electron density distribution function (RDF) is characterised by a well developed first coordination sphere, R Ge–S, located at 2.26 ± 0.03 Å indicating the existence of GeS 4 tetrahedra. Simultaneously, another well developed coordination sphere, R Ag–S, exists at 2.63 ± 0.05 Å and can be ascribed to Ag–S interactions. With increasing x the sphere corresponding to Ge–S interactions decreases while the sphere corresponding to Ag–S interactions increases. Model calculations based on a statistical mixture of GeS 4 and AgS 4 tetrahedra explain the above tendency well. At the same time, a more dense packing of GeS 4 tetrahedra than in GeS 2 is indicated for concentrations x → 0.6 at least in a part of the network characterised by a GeS-like contribution.