VIBRATIONAL-SPECTRA AND STRUCTURE OF AS-P-S GLASSES

A structural model for As-P-S glasses is proposed from an analysis of Raman and infrared spectra of two series of glasses with compositions (As2S3)1-x(P2S5)x with x = 0-0.7 and As(x)P(x)S1-2x with x = 0.10-0.16. The structural network in these glasses is composed of AsS3/2 and S = PS3/2 structural units forming 8-membered rings of As2P2S4. The Raman spectra of these glasses are characterized by a sharp strong Raman band of 418 cm-1 ascribed to the breathing vibration of the rings. In the S-rich compositional region lying under the As2S3-P2S5 line, towards the S corner of the As-P-S phase diagram, sulfur atoms form S8 molecules inside the structural network. In the P-31 MAS-NMR spectrum by a single line with the chemical shift delta(P-31) = 113.4 ppm is due to the S = PS3/2 Coordination of the phosphorus atom.