Cluster formation in symmetric binary SALR mixtures

Abstract

The equilibrium cluster fluid state of a symmetric binary mixture of particles interacting through short-ranged attractive (SA) and long-ranged repulsive (LR) interactions is investigated through Monte Carlo simulations. We find the clustering behavior for this system is controlled by the cross-interaction between the two types of particles. For a weak cross-attraction, the system displays behavior that is a composite of the behavior of the individual components, i.e. the two components can both form giant clusters independently and the clusters distribute evenly in the system. For a strong cross-attraction, we instead find the resulting clusters are mixtures of both components. Between these limits, both components can form relatively pure clusters, but unlike clusters can join at their surfaces to form composite clusters. These insights should help to understand the mechanisms for clustering in experimental binary mixture systems, and help tailor the properties of novel nanomaterials.

Competition between clustering and phase separation in binary mixtures containing SALR particles

“…Finally increasing the range of attraction to n = 5 (SW width E1.21s), panel C, the scenario changes again and a single big cluster encompassing almost all particles becomes stable. This outcome differs from the observation of giant clusters by Sweatman and coworkers in a mixture with shortrange interspecies attraction: 49,50 in that case, the formation of several clusters of large size was reported at equilibrium. Here, we instead find a single big cluster containing most of the particles in the sample.…”

“…Evidence of similarly large clusters has also been reported in ref. 49 and 50. In all these cases, the structure factor exhibits a first peak centred at k ≠ 0, see Fig.…”

“…55) encompassing all particles. The need for a double check emerges from previous studies of SALR particles 37 and their mixtures, 49,50,52 where giant clusters have occasionally been observed at equilibrium. For n r 3 equilibrium is typically attained after 5 Â 10 5 MC cycles; for n = 4, as many as 2 Â 10 7 MC cycles are required to equilibrate the system.…”

“…In particular, upon tuning the size of monomers making up the dimer and using monomer-specific interactions with the second species, it is possible to obtain a large variety of selfassembling structures, including vesicles 46 and coating shells (capsules). 47,48 A second possibility would be to consider a mixture of monatomic species with various types of SALR potentials: [49][50][51][52] leveraging on the interactions, one can produce microphases exhibiting many different kinds of stable aggregates.…”

Colloidal Soft Matter Physics

“…Thus, one not only deal with the competition at the level of the interparticle potential, now one has to take into account the competition between different length scales. As a result, one can find that, for example, the clustering behavior in this asymmetric mixture is controlled by the cross-interaction between the two types of colloidal particles [136]. Thus, one can control the resulting degree of aggregation by simply tuning the size asymmetry of the suspension.…”