Structural Origin of Fragility in Ge-As-S Glasses Investigated b...

The fragility index (m) of a series of Ge-As-S glasses covering a wide range of mean coordination (< r>) and stoichiometry is measured by differential scanning calorimetry. The evolution of the fragility index appears to be better predicted by the stoichiometry than the mean coordination, and m shows a well-defined dependence on the departure from stoichiometry quantified as the at. % excess or deficiency in sulfur. The effect of stoichiometry on the fragility of Ge-As-S glasses is very similar