On the relaxation dynamics of glass-forming systems: Insights from computer simulations

TL;DR

This paper investigates the relaxation dynamics in a lattice gas model for glass-forming systems, revealing heterogeneous motion, density-dependent relaxation, and exponential tails in displacement distributions, supported by simulations and a simple random walk model.

Contribution

It introduces a simple lattice gas model to study heterogeneous relaxation dynamics and connects these findings with experimental observations through a random walk approach.

Findings

Relaxation slows rapidly with increasing density.

Particle motion is spatially and temporally heterogeneous.

Displacement distributions exhibit exponential tails for large displacements.

Abstract

We discuss the relaxation dynamics of a simple lattice gas model for glass-forming systems and show that with increasing density of particles this dynamics slows down very quickly. By monitoring the trajectory of tagged particles we find that their motion is very heterogeneous in space and time, leading to regions in space in which there is a fast dynamics and others in which it is slow. We determine how the geometric properties of these quickly relaxing regions depend on density and time. Motivated by this heterogeneous hopping dynamics, we use a simple model, a variant of a continuous time random walk, to characterize the relaxation dynamics. In particular we find from this model that for large displacements the self part of the van Hove function shows an exponential tail, in agreement with recent findings from experiments and simulations of glass-forming systems.