Optical-absorption-edge measurements and Raman scattering experiments on ${\mathrm{Ge}}_x{\mathrm{Se}}_{1-x}$ glasses are reported for the range $0\le x\le 0.4$. The change in the magnitude of the main peaks of Raman spectra (localized about 195, 215, and 250 ${\mathrm{cm}}^{-1\mathrm{}}$) and the variation of the optical-absorption edge as a function of $x$ lead to a model of local structure for $x\le \frac{1}{3}$. In this range of concentrations, germanium atoms are coordinated with four selenium atoms. There is no Ge-Ge bond, and furthermore, Ge-Se-Ge sequences remain scarce as long as the germanium concentration of the mixture makes it possible.

• Received 9 April 1973

DOI:https://doi.org/10.1103/PhysRevB.8.5947