A numerical study of one-patch colloidal particles: from square-well to Janus

TL;DR

This study uses numerical simulations to explore how the phase behavior and structure of one-patch colloidal particles evolve from spherical to Janus configurations, revealing unique clustering and phase coexistence phenomena.

Contribution

It introduces a detailed numerical analysis of the transition from spherical to Janus particles and their collective structures, highlighting the formation of micelles and vesicles.

Findings

Formation of orientational micelles and vesicles in Janus particles

Unusual gas-liquid coexistence with increasing gas density at lower temperatures

Low-temperature behavior approximates a fluid of clusters interacting via excluded volume

Abstract

We perform numerical simulations of a simple model of one-patch colloidal particles to investigate: (i) the behavior of the gas-liquid phase diagram on moving from a spherical attractive potential to a Janus potential and (ii) the collective structure of a system of Janus particles. We show that, for the case where one of the two hemispheres is attractive and one is repulsive, the system organizes into a dispersion of orientational ordered micelles and vesicles and, at low $T$, the system can be approximated as a fluid of such clusters, interacting essentially via excluded volume. The stability of this cluster phase generates a very peculiar shape of the gas and liquid coexisting densities, with a gas coexistence density which increases on cooling, approaching the liquid coexistence density at very low $T$.