Interpretation of the molten BeF₂ viscosity anomaly in terms of a high temperature density maximum, and other waterlike features

Ion dynamics computer simulations of BeF₂ were carried out over a temperature range which overlapped with the experimental viscosity data. Diffusivity data was obtained using the simple rigid ion potentials. A highly anomalous region of behavior was shown by the diffusivity data at temperatures just above the limits of laboratory measurement, which reconciled the observed viscosity with that of other liquids. Interpretion of this strongly curved region was done in terms of a strongly negative liquid expansivity regime associated with a large heat capacity regime using the Adams-Gibbs equation. The fragility of the BeF₂ and SiO₂ was shown to greatly exceed that of Lennard-Jones liquids.