Lifetime of dynamical heterogeneity in a highly supercooled liquid

TL;DR

This study uses molecular dynamics simulations to analyze the lifetime of dynamical heterogeneity in supercooled liquids, revealing that the heterogeneity's lifetime varies significantly with the chosen time interval and temperature.

Contribution

It introduces a method to quantify the lifetime of dynamical heterogeneity in supercooled liquids using four-point correlation functions at different time intervals.

Findings

Heterogeneity lifetime increases as temperature decreases.

Lifetime at $ au_ ext{alpha}$ becomes much larger than $ au_ ext{alpha}$ at low temperatures.

Lifetime at $ au_{ ext{ngp}}$ remains comparable to $ au_ ext{alpha}$ across temperatures.

Abstract

We numerically examine dynamical heterogeneity in a highly supercooled three-dimensional liquid via molecular-dynamics simulations. To define the local dynamics, we consider two time intervals, $\tau_\alpha$ and $\tau_{\text{ngp}}$. $\tau_\alpha$ is the $\alpha$ relaxation time, and $\tau_{\text{ngp}}$ is the time at which non-Gaussian parameter of the van Hove self-correlation function is maximized. We determine the lifetimes of the heterogeneous dynamics in these two different time intervals, $\tau_{\text{hetero}}(\tau_\alpha)$ and $\tau_{\text{hetero}}(\tau_{\text{ngp}})$, by calculating the time correlation function of the particle dynamics, i.e., the four-point correlation function. We find that the difference between $\tau_{\text{hetero}}(\tau_\alpha)$ and $\tau_{\text{hetero}}(\tau_{\text{ngp}})$ increases with decreasing temperature. At low temperatures, $\tau_{\text{hetero}}(\tau_\alpha)$ is considerably larger than $\tau_{\alpha}$, while $\tau_{\text{hetero}}(\tau_{\text{ngp}})$ remains comparable to $\tau_{\alpha}$. Thus, the lifetime of the heterogeneous dynamics depends strongly on the time interval.