Structural investigations of the Se–Ag–I system

Glasses from the Se–Ag–I system have been investigated. Structural information is gathered based on results collected by a combination of several types of diffraction measurements. First coordination sphere at r =2.3–2.5 Å determined by radial distribution function calculations can be assumed to be composed by Se–Ag and Ag–I correlations in the network units and Se–Se correlation in the Se cluster units. The interatomic distances and average bond angles decrease with the introduction of additives to selenium. The Raman spectra reveal that the introduction of silver and iodine, in particular, brings about a shift of the Se chain stretching mode towards lower wave numbers (251–236 cm ⁻¹). Apparently, the newly formed structure after the introduction of additives into selenium is pretty compact and is becoming more covalent with a stronger interchain interaction. Depending on the concentration of additives the breathing modes of Ag–Se and Ag–I bonds also can be seen.