Phase diagram and structural properties of a simple model for one-patch particles

Abstract

We study the thermodynamic and structural properties of a simple, one-patch fluid model using the reference hypernetted-chain (RHNC) integral equation and specialized Monte Carlo simulations. In this model, the interacting particles are hard spheres, each of which carries a single identical, arbitrarily-oriented, attractive circular patch on its surface; two spheres attract via a simple squarewell potential only if the two patches on the spheres face each other within a specific angular range dictated by the size of the patch. For a ratio of attractive to repulsive surface of 0.8, we construct the RHNC fluid-fluid separation curve and compare with that obtained by Gibbs ensemble and grand canonical Monte Carlo simulations. We find that RHNC provides a quick and highly reliable estimate for the position of the fluid-fluid critical line. In addition, it gives a detailed (though approximate) description of all structural properties and their dependence on patch size.

Janus fluid with fixed patch orientations: Theory and simulations

“…7 In fact, one of the most attractive features of the general model stems from the fact that it smoothly interpolates between an isotropic HS fluid (zero coverage) and an equally isotropic SW fluid (full coverage). 8,9 The thermophysical and structural properties of the Janus fluid have been recently investigated within the framework of the Kern-Frenkel model using numerical simulations, 7,10 thus rationalizing the cluster formation mechanism characteristic of the experiments. 3 The fluidfluid transition was found to display an unconventional and particularly interesting phase diagram, with a reentrant transition associated with the formation of a cluster phase at low temperatures and densities.…”

Molecular theory for the phase equilibria and cluster distribution of associating fluids with small bond angles

“…There has also been an extensive number of theoretical and simulation studies on the thermodynamics, phase behavior, and self-assembly of patchy colloid fluids. [8][9][10][11][12][13][14][15][16][17][18][19][20][21] Patchy colloids are typically modeled using Wertheim's first order perturbation theory (TPT1) and a potential model for conical association sites introduced by Bol 22 and later Chapman 23 that became widely used in the patchy colloid community after Kern and Frenkel 24 introduced this potential as a primitive model for patchy colloids. a) Author to whom correspondence should be addressed.…”

Self-assembly mechanism in colloids: perspectives from statistical physics

“…It has few shortcomings and several advantages, compared to other possible closures, that have been analyzed in detail in past work [19][20][21]. Its main advantage here is related to its ability of computing the chemical potential and pressure without invoking additional approximations besides those included in the closure [16][17][18]. For a fixed temperature T * , one can then compute the pressure of the gas (colloidal poor) phase P * and of the liquid (colloidal rich) P * phases, and the corresponding chemical potentials µ * and µ * .…”

“…The case of angular dependent anisotropic potentials is far more complex from the algorithmic point of view, but the philosophy behind the methodology is identical. It was devised in the frame of molecular fluids [32], and more recently adapted to the case of patchy colloids [17,18]. Here we just sketch the idea, referring to Refs.…”

“…Two schemes will be discussed, both hinging on classical concepts in statistical physics. The first one is an adaptation to patchy colloids of the usual integral equation theory [16][17][18], and is patterned after a similar technique applied to molecular fluids [19][20][21][22]. This will be discussed in Section 4.1.…”