Particle Monte Carlo simulation of string-like colloidal assembly in 3 dimensions

TL;DR

This study extends previous 2D simulations to 3D, demonstrating that polymer-grafted colloids with purely repulsive interactions can form string-like assemblies, with critical behavior observed at phase transition points.

Contribution

It provides the first 3D simulation evidence of string-like colloidal assembly with purely repulsive interactions, analyzing their statistical properties and phase transition behavior.

Findings

String-like assemblies exist in 3D systems.

Average string length diverges at phase transition points.

String formation occurs despite purely repulsive interactions.

Abstract

As an extension of the former study on 2-dimensional systems, we simulate phase behavior of polymer-grafted colloidal particles in 3 dimensions by molecular Monte Carlo technique in the canonical ensemble. We use a spherically symmetric square-step repulsive interaction potential, which has been obtained using self-consistent field calculation. In previous articles, we have studied these model colloids in 2 dimensions and found that these particles, although their interaction is purely repulsive, self-assemble into a string-like assembly, in a narrow region of physical parameter sets. In the present work, we show the existence of the string-like assembly in 3-dimensional systems and study the statistical properties of the arrangement of these strings. The average string length diverges around the region where the melting transition line and the percolation transition line cross, which has also been found in 2 dimensions.