Far-infrared spectra and bonding arrangement in Ge-As-S-Se glasses

Bulk glasses of formal chemical composition (GeSe2)(x)(As2S3)(1-x) were prepared by melting presynthesized As2S3 and elemental germanium and selenium. The values of hydrostatic density, optical gap, Urbach edge slope, refractive index, glass-transition and softening temperatures were determined. Measured far-infrared spectra were analysed in terms of two models, one in which bonds between cations (Ge and As) and anions (S, Se) form randomly and a second in which bond-strength between cations and anions is maximized in assembling the network. The analysis reveals preference fur the second model, which suggests that in studied glasses the formation of Ge-S bonds is enhanced in the region 0 < x < 1. (C) 2000 Elsevier Science Ltd. All rights reserved.