Consequences of the superstrong nature of chalcogenide glass-forming liquids at select compositions

Growth of homogeneous melts of stoichiometric compositions of chalcogenides is facilitated by underlying crystalline phases. Such is not the case for non-stoichiometric melt compositions in which, for example, variation of fragility (m) from complex specific heat measurements show global minimum [1] at an extremely low value (m$=$14.8(0.5)) in the 21.5{\%} \textit{\textless }x \textit{\textless }23{\%} range of Ge in homogenized Ge$_{x}$Se$_{100-x} $melts. This has unwittingly led to variability of results in physical properties of \textit{non-stoichiometric} melts/glasses due to their heterogeneity. By directly mapping melt stoichiometry variation along a quartz tube as a function of reaction time of starting materials at a fixed temperature T\textit{\textgreater }T$_{g}$ over days, we have observed a slowdown [1] of melt-homogenization by the super-strong melt compositions, 21.5{\%} \textless x \textit{\textless }23{\%}. This range, furthermore, appears to be correlated to the one observed between the ?exible and stressed rigid phase in network glasses.\\[4pt] [1] K.Gunasekera et al. , J.Chem Phys. 139, 164511 (2013).