The Universality of Cooperative Fluctuations in Glass-Forming Supercooled Liquids.

Amorphous glasses are formed by rapid cooling of the melt to avoid crystallization. The vitrification temperature increases with increasing the cooling rate. The viscosity of the supercooled melt and the vitrification are related to the atomic or molecular mobility, which in turn is linked to the dynamic heterogeneities and the size of cooperative rearrangement regions (CRR). The temperature dependence of the average correlation length of the CRR, ξ, for organic compounds, polymers, chalcogenide glass formers and metallic glass formers with a fragility index m ≥ 40 was investigated. The results show an almost material-independent variation of ξ as a function of the reduced reciprocal temperature Tg/T, where Tg is the glass transition temperature. This suggests that ξ(Tg/T) is a universal function for all the investigated glass formers. It was also found that ξ and the activation energy of the α-relaxation are proportional to each other. Furthermore, relations between the macroscopic parameters of the glass-forming kinetics were identified.