Fragile-strong transitions and polyamorphism in glass former fluids

Abstract

A simple model of a glass former fluid, consisting of a bidisperse mixture of penetrable spheres is studied. The model shows a transition from fragile to strong behavior as temperature is reduced. This transition is driven by the competition between the two mechanisms that contribute to diffusivity in the model: collective rearrangement of particles (responsible for the fragile behavior), and individual particle motion (which gives rise to the strong behavior at low temperature). We also observe a maximum of diffusivity as a function of pressure that can be interpreted within the same framework. The connection between this behavior and polyamorphism is addressed.