Covalent bond connectivity, medium range order and physical properties of GexIn8Se92-x glasses

The GexIn8Se92-x glasses (14 <= x <= 23.5) were extensively characterized by X-ray diffraction (XRD). The chemical composition is determined using energy dispersive spectrometers (EDS). The atomic structure of these glasses is investigated by using (XRD) technique. The first sharp diffraction peak (FSDP) in the structural factor indicates the existence of medium range order (MRO) in these glasses. The position of the FSDP and its full width at half maximum (FWHM), obtained after fitting the XRD of the glasses. The repetitive characteristic distance, R and structural correlation length, L, which characterizing the intermediate structure are deduced. The effect of composition and average coordination number <CN>, on the atomic volume, the density and compactness are studied. The connectivity of the system is discussed in terms of the total number of constraints which also influence the mean bond energy of the system. The intensity of the FSDP, the atomic volume and compactness of the structure, have anomalous change at <CN> = 2.67 indicating, a topological threshold occurs. The occurrence of this dependence leads to the Ge content has a marked effect on the MRO and physical properties parameters. (C) 2013 Elsevier Masson SAS. All rights reserved.