FORMATION AND VIBRATION-SPECTRA OF HGI2-AG2S-AS2S3 AND HGS-AG2S-AS2S3 SYSTEM GLASSES

Glass-forming regions of HgI2-Ag2S-As2S3 and HgS-Ag2S-AS2S3 systems have been obtained. The two systems have large glass-forming regions. The structures of these glasses have been investigated by means of far-infrared transmission spectra and Raman spectra. Based on interpretations of the IR and Raman spectra, the following structures are proposed. The ring groups of As3S6 are formed with the addition of Ag2S into AS2S3 glass. The structural units of AsI3-xSx (x = 0, 1, 2) pyramids and HgI4-xSx (x = 0, 1, 2) tetrahedra are formed with the addition of HgI2 into As2S3. The interconnection between the AsS3 pyramids and the HgI4 tetrahedra is through the coordinate bonds formed by the empty orbitals of Hg atoms in HgI2 and the lone-pair electrons of S atoms in As2S3. This connection composes the network of HgI2-As2S3 glasses. The structure of HgS-Ag2S-As2S3 glasses is composed of AsS3 pyramids, As3S, rings, AgS6 and HgS6 octahedra. The interconnection between AsS3 and these polyhedra is through the sulfur bridges or sharing the edges of these polyhedra.