Transition thresholds in GexAsySe1-x-y glasses

We designed and prepared several groups of glasses with a mean coordination number (MCN) from 2.2 to 2.94 in order to explore the effect of MCN and chemical compositions on the physical properties of the glasses. We found that, while glass transition temperature increases with increasing MCN, the density and elastic moduli of the glasses show two transition thresholds at MCN=2.45 and 2.65, respectively. Raman scattering measurements indicate that the former corresponds to merging of the 225cm-1 and 250cm-1 modes which is a symbol of the extinction of free Se, while the latter corresponds to the appearance of two new modes at 280-290cm-1 and 170cm-1 that come from the defect modes of ethanelike Ge2Se6/2. The analysis of the experimental results on the glasses with same MCN but different chemical compositions suggest that, while MCN is a primary factor to determine the physical properties of the ternary glasses, the chemical compositions could be second factor to tune the physical properties