Meeting experimental challenges to physics of network glasses: Assessing the role of sample homogeneity

We introduce a Raman profiling method to track homogenization of Ge_xSe_100−x melts in real time, and show that 2 g melts reacted at 950 °C in high vacuum homogenize in 168 h on a scale of 10μm. Homogenization of melts is precursive to self-organization of glasses. In the present glasses, compositional variation of Raman active corner-sharing mode frequency of GeSe₄ units, molar volumes, and the enthalpy of relaxation at T_g, reveal the rigidity (x_c(1)=19.5(3)%) and the stress (x_c(2)=26.0(3)%) transitions to be rather sharp (Δx<0.6%). These abrupt elastic phase transitions are in harmony with rigidity theory and have a direct bearing on the physics of glasses.