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

The theory developed in our previous papers [Phys. Rev. E 99, 030101(R) (2019); 103. 032611 (2021)] 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 the 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 the dynamics of glass-forming liquids.

Automated summary

This paper applies a theory developed in previous works to investigate the slowing down of dynamics of glass-forming liquids in relation to attractive and repulsive intermolecular interactions. By comparing a Lennard-Jones glass-forming liquid and its simplified model, the study reveals that differences in local structures and parameters psi(T) and T-a significantly impact the dynamics of the two systems. The findings suggest that intermolecular interactions play a crucial role in determining the dynamics of glass-forming liquids.