Particle Monte Carlo simulation of string-like colloidal assembly in 2 dimensions

TL;DR

This study uses Monte Carlo simulations to explore how purely repulsive, polymer-grafted colloids self-assemble into string-like structures in two dimensions, revealing critical behavior related to percolation and phase transitions.

Contribution

It demonstrates that purely repulsive colloids can form string-like assemblies and identifies a critical point where percolation and melting transitions intersect.

Findings

String-like assemblies form at low temperature and high density.

Average string length diverges at the intersection of phase transition lines.

Percolation phenomena are closely related to the assembly behavior.

Abstract

We simulate structural phase behavior of polymer-grafted colloidal particles by molecular Monte Carlo technique. Interparticle potential, which has a finite repulsive square-step outside a rigid core of the colloid, was previously confirmed via numerical self-consistent field calculation. This model potential is purely repulsive. We simulate these model colloids in the canonical ensemble in 2 dimensions and find that these particles containing no interparticle attraction self-assemble and align in a string-like assembly, at low temperature and high density. This string-like colloidal assembly is related to percolation phenomena. Analyzing the cluster size distribution and the average string length, we build phase diagrams and discover that the average string length diverges around the region where the melting transition line and the percolation transition line cross. This result is similar to Ising spin systems, in which the percolation transition line and the order-disorder line meet at a critical point.