How attractive and repulsive interactions affect structure ordering and dynamics of glass-forming liquids?

TL;DR

This paper investigates how attractive and repulsive interactions influence the structure and dynamics of glass-forming liquids, revealing key differences in local structures and relaxation behavior through theoretical and simulation comparisons.

Contribution

The study extends a theoretical framework to distinguish the effects of attractive and repulsive forces on glass dynamics, highlighting structural differences despite similar pair correlations.

Findings

Different local structures in Lennard-Jones and WCA systems at similar dynamics.

The parameter ψ(T) links fluctuations to cluster size and crossover temperature.

The theory aligns well with simulation results, elucidating dynamics determinants.

Abstract

The theory developed in our previous papers is applied in this paper to investigate the dependence of slowing down of dynamics of glass-forming liquids on the attractive and repulsive parts of intermolecular interactions. Through an extensive comparison of the behavior of a Lennard-Jones glass-forming liquid and that of its WCA reduction to a model with truncated pair potential without attractive tail, we demonstrate why the two systems exhibit very different dynamics despite having nearly identical pair correlation functions. In particular, we show that local structures characterized by number of mobile and immobile particles around a central particle markedly differ in the two systems at densities and temperatures where their dynamics show large difference and nearly identical where dynamics nearly overlap. We also show how the parameter {\psi}(T ) that measures the role of fluctuations embedded in the system on size of the cooperatively reorganizing cluster (CRC) and the crossover temperature T a depend on the intermolecular interactions. These parameters stemming from the intermolecular interactions characterize the temperature and density dependence of structural relaxation time {\tau} {\alpha}. The quantitative and qualitative agreements found with simulation results for the two systems suggest that our theory brings out the underlying features that determine dynamics of glass-forming liquids.