`Strong' and `superstrong' liquids, and an approach to the perfect glass state via phase transition

When the excitations described by the `bond lattice' model, and its `defect' model relatives, are allowed to interact, this simple class of model predicts the possibility of first-order transitions between viscous and fluid liquid states. Looking for support of this prediction, the behavior of a series of `tetrahedral' liquids, all of which are famous for one or another aspect of their behavior, was examined. It is shown that when diffusivity data for these liquids, SiO<sub>2</sub>, BeF<sub>2</sub>, water, and liquid Si, are plotted on a reduced temperature scale with glass transition temperature as the scaling temperature, a systematic pattern is revealed in which a mild deviation, in the case of BeF<sub>2</sub>, from the `strong' extreme of the normal strong/fragile glass-former pattern.