Lifetime of dynamic heterogeneities in a binary Lennard-Jones mixture

TL;DR

This paper uses computer simulations to analyze the lifetime of dynamic heterogeneities in a binary Lennard-Jones mixture, comparing different methods of selecting slow sub-ensembles and their relation to alpha relaxation.

Contribution

It introduces a four-time correlation function approach to measure the lifetime of dynamic heterogeneities in a simulated binary Lennard-Jones mixture, linking it to experimental NMR techniques.

Findings

The four-time correlation function effectively characterizes the lifetime of heterogeneities.

Lifetimes of slow sub-ensembles differ depending on the selection method.

The heterogeneity lifetime is comparable to the alpha relaxation time.

Abstract

A four-time correlation function was calculated using a computer simulation of a binary Lennard-Jones mixture. The information content of the four-time correlation function is similar to that of four-time correlation functions measured in NMR experiments. The correlation function selects a sub-ensemble and analyzes its dynamics after some waiting time. The lifetime of the sub-ensemble selected by the four-time correlation function is calculated, and compared to the lifetimes of slow sub-ensembles selected using two different definitions of mobility, and to the $\alpha$ relaxation time.