Predicting the Phase Diagram of Two-Dimensional Colloidal Systems with Long-Range Interactions

Abstract

The phase diagram of a two-dimensional model system for colloidal particles at the air-water interface was determined using Monte Carlo computer simulations in the isothermic-isobaric ensemble. The micrometerrange binary colloidal interaction has been modeled by hard disklike particles interacting via a secondary minimum followed by a weaker longer-range repulsive maximum, both of the order of k B T. The repulsive part of the potential drives the clustering of particles at low densities and low temperatures. Pinned voids are formed at higher densities and intermediate values of the surface pressure. The analysis of isotherms, translational and orientational correlation functions as well as structure factor gives clear evidence of the presence of a melting first-order transition. However, the melting process can be also followed by a metastable route through a hexatic phase at low surface pressures and low temperatures, before crystalization occurs at higher surface pressure.

Molecular Thermodynamics of Adsorption using Discrete-Potential Systems

“…Instead of a liquid-liquid transition that has been evidenced in 3D DP systems, a metastable hexactic transition appears between a liquid and the two types of crystals. This suggests that a liquid-hexactic instead of a liquid-liquid transition could be present in 2D DP systems [21].…”

“…The case of two-dimensional DP systems has its specific interest. The behaviour of colloidal particles located at the air-water interface has been succesfully modelled using two-dimensional discrete-potential systems [20,21].…”

Computer simulation of liquid-vapor coexistence of confined quantum fluids

“…Whereas the classical system clearly shows a liquid-vapor transition, the quantum system presents a modulated phase with the presence of voids, similar to the phases observed for 2D disks systems. 86,87 The trend observed for the classical LJ fluid is that just for L p = 2σ there is evidence of a 3D-2D crossover in the behavior of the critical temperature T * c . 70 Although in the quantum case was not possible to determine T * c when L p /σ < 2, the similarity between phases with 2D-systems suggest a dimensional crossover although the liquid-vapor transition could be already lost.…”

Monte Carlo simulation of flexible trimers: From square well chains to amphiphilic primitive models

“…33 Colloidal particles at the air-water interface also present different structural arrangements like stripes, voids, foams, and chain formation that can be modeled by computer simulation with continuous or discrete-potential systems. [34][35][36] Janus colloidal particles, [37][38][39] where two opposite chemical functionalities are attached to the same particle introducing strong competing effects and inducing novel phases, have received a considerable amount of interest due to their wide range of applications 40 and have been studied in relation to their micellization process. 41 In this work, we study a primitive model of selfassembling discrete-potential system in order to understand its phase diagram.…”