Dynamic heterogeneity and non-Gaussian behaviour in a model supercooled liquid

Abstract

We use a recently derived reformulation of the diffusion constant (Stillinger andDebenedetti 2005 J. Phys. Chem. B 109 6604) to investigate heterogeneousdynamics and non-Gaussian diffusion in a binary Lennard-Jones mixture. Ourwork focuses on the joint probability distribution of particles with velocityv0 at timet = 0 and eventualdisplacement Δx at time t = Δt. We show that this distribution attains a distinctive shape at the time of maximumnon-Gaussian behaviour in the supercooled liquid. By performing a two-Gaussian fit of thedisplacement data, we obtain, in a non-arbitrary manner, two diffusive length scalesinherent to the supercooled liquid and use them to identify spatially separated regions ofmobile and immobile particles.