Characteristic length of dynamic glass transition near T-g for a wide assortment of glass-forming substances

Dynamic heterogeneity is an. active field of glass-transition research. The length scale of this heterogeneity is called the characteristic length. It can be calculated from complex heat capacity curves in the equilibrium liq uid or from dynamic calorimetry curves corrected with regard to nonequilibr ium. No molecular parameters or microscopic models are necessary for obtain ing the length. We report the characteristic length near glass temperature for about 30 glass formers including small-molecule liquids, polymers, sili cate glasses, a metallic glass, a Liquid crystal, and a plastic crystal. Th e lengths are between 1.0 and 3.5 nm with certain cumulations between 1.0 a nd 2.0 nm and between 2.5 and 3.5 nm. To try a correlation to other propert ies, we find that at least two should be included, e.g., Angell's fragility and the distance of T-g from the crossover temperature, T-c.