The influence of bond-rigidity and cluster diffusion on the self-diffusion of hard spheres with square-well interaction

TL;DR

This study compares simulation methods for hard spheres with square-well interactions, revealing how bond rigidity and hydrodynamics influence self-diffusion, with BCD providing insights into bond and hydrodynamic effects.

Contribution

It demonstrates the impact of bond rigidity and hydrodynamic interactions on self-diffusion in square-well systems using BCD and EDBD methods, highlighting differences in diffusion behavior.

Findings

Bond rigidity significantly decreases self-diffusion coefficient.

Hydrodynamic interactions slightly increase self-diffusion.

Self-diffusion exhibits a maximum at intermediate attraction strength.

Abstract

Hard spheres interacting through a square-well potential were simulated using two different methods: Brownian Cluster Dynamics (BCD) and Event Driven Brownian Dynamics (EDBD). The structure of the equilibrium states obtained by both methods were compared and found to be almost the identical. Self diffusion coefficients ($D$) were determined as a function of the interaction strength. The same values were found using BCD or EDBD. Contrary the EDBD, BCD allows one to study the effect of bond rigidity and hydrodynamic interaction within the clusters. When the bonds are flexible the effect of attraction on $D$ is relatively weak compared to systems with rigid bonds. $D$ increases first with increasing attraction strength, and then decreases for stronger interaction. Introducing intra-cluster hydrodynamic interaction weakly increases $D$ for a given interaction strength. Introducing bond rigidity causes a strong decrease of $D$ which no longer shows a maximum as function of the attraction strength.