Descriptors for mobility of thermal and athermal glass-forming systems

The temperature dependence of mobility of glass-forming systems while in the super-Arrhenian regime is a long-standing unsolved problem in condensed matter physics. Previous work by our group has shown that a simple function of the mean squared force on a molecule is able to describe the temperature dependence of the translational diffusivity across both the Arrhenian and super-Arrhenian regimes across three distinct molecular dynamics. It is known that athermal systems, including colloidal and hard sphere systems, exhibit a sharp decrease in mobility with increase in volume fraction. Force based formula is not applicable to such systems. Event-driven computer simulations of polydisperse hard sphere systems have been performed across a range of volume fractions. The variance of the distance to the nearest molecule and the variance in the Voronoi volume per molecule have been identified as descriptors, that when using the same mapping as for the mean squared force, lead to linearization of mobility across the Arrhenian and super-Arrhenian regimes for the hard sphere system as well as the thermal systems previously investigated.