Figure 4: A summary of experimentally measured fragilities in glass network-forming melts.

Experimental fragilities as a function of a rescaled composition corresponding to the centroid x_c of the corresponding isostatic window (or Boolchand phase): Ge–S²⁷, Ge–Se³, As–Se²⁸, Ge–Sb–Se²⁹, Si–Ge–Te. All display a minimum at or close to x=x_c. Note that the minimum for Ge–Si–Te is clearly visible if represented on an appropriate scale³⁰. The trend in composition for TeO₂–V₂O₅ is highlighted by a thin broken line (P. Boolchand, unpublished results). The solid line is a global quadratic fit to the whole data sets, and serves only as guide. Stoichiometric compounds are signalled.