Rigidity percolation and structure of Ge-Se system

We have investigated low-frequency Raman spectra of glassy GexSe1-x (x = 0- 0.40) in a range of 3-100 cm(-1) A relative degree of fragility was first o btained in the Ge-Se system by an investigation of the line shape of low-fr equency Raman spectra. The results imply an important relationship between the changes of fragility and the structural changes. The rapid drop of the fragility at average coordination number, [r], of 2.4 (x = 2.0) is consider ed as evidence for the rigidity threshold predicted by the mean-field const raint counting procedures. (C) 1999 Elsevier Science B.V. All rights reserv ed.