Ergodicity and activated dynamics in supercooled liquids

Abstract

We show, using constant-pressure molecular-dynamics calculations, that the deviation from Arrhenius behavior in transport properties in the supercooled states of Lennard-Jones (LJ) fluids and soft-sphere (SS) systems starts to occur when the time scale for obtaining ergodicity starts to increase dramatically. The temperature dependence of the ergodicity diffusion parameter for both the SS mixtures and the two-component LJ system follows the Vogel-Fulcher (VF) equation. The self-diffusion constants for the SS mixtures follows the Arrhenius law, whereas for the LJ system a VF behavior is found. Our results also demonstrate that relaxation processes in supercooled liquids are dominated by fluctuations in domains of finite length.