TOPOLOGICAL TRANSITION AND RIGIDITY PERCOLATION IN GE-SE(S)-CD GLASSES

The glass-forming region in the GeSe-Cd system has been determined, wh ere up to 12 at.% Cd can be introduced into the binary Ge20Se80 compos ition. Specific features in the compositional dependence of the densit y, cl, and microhardness, H-m, on the average coordination number, Z, have been found. In particular, two extrema have been observed at Z = 2.4 and Z = 2.68, both in bulk glasses and in amorphous films of the G exSe98-xCd2 family, but the effects are less in the latter case. The s ame regularities have also been established for the glassy Ge-S-Cd sys tem. The results obtained are compared with those for the previously s tudied Ge-Se-Fe system. They are discussed on the basis of rigidity pe rcolation concepts and in terms of topological structural transitions in chalcogenide glasses. (C) 1998 Elsevier Science B.V. All rights res erved.