Unification of temperature dependence of mobility in the Arrhenian and super-Arrhenian region

A long-standing unsolved problem in condensed matter physics is a fundamental understanding of the temperature dependence of the relaxation time of glass forming materials. Experimentally, the log a mobility as a function of temperature shows two distinct regimes above and below T_α, one Arrhenian and the other super-Arrhenian, respectively. The change in the temperature response of the mobility at T_α suggests a structural change in the material which must affect other properties of the system. Using molecular dynamics simulations, a search for other physical quantities that change behavior at T_α has been carried out on three different model glass forming systems. Several molecular descriptors which change their temperature dependence at T_α have been identified, including the mean squared force applied to a molecule. We propose a mapping between these descriptors and log a that results in the linearization of the log a data across the entire range, including both the Arrhenian and super-Arrhenian regions. The conclusion holds for all model glass forming systems investigated, including a binary LJ mixture, LJ dumbbells and a coarse-grained OTP model.