Fluid–fluid coexistence in colloidal systems with short-ranged strongly directional attraction

Abstract

We present a systematic numerical study of the phase behavior of square-well fluids with a ''patchy'' short-ranged attraction. In particular, we study the effect of the size and number of attractive patches on the fluid-fluid coexistence. The model that we use is a generalization of the hard sphere square well model. The systems that we study have a stronger tendency to form gels than the isotropic square-well system. For this reason, we had to combine Gibbs ensemble simulations of the fluidfluid coexistence with a parallel tempering scheme. For moderate directionality, changes of the critical density and the width of coexistence curves are small. For strong directionality, however, we find clear deviations from the extended law of corresponding states: in contrast to isotropic attractions, the critical point is not characterized by a universal value of the reduced second virial coefficient. Furthermore, as the directionality increases, multiparticle bonding affects the critical temperature. We discuss implications for the phase behavior, and possibly crystallization, of globular proteins.

Fabrication, Assembly, and Application of Patchy Particles

“…The model enables variation of the total surface coverage and the geometrical distribution of the adhesion. Gögelein et al [127] modify the two-patch patchy model description proposed by Kern and Frenkel [135] by replacing the square-well potential with an attractive Yukawa-type potential to describe lysozyme dispersions. The parameters used for the Yukawa-type potential are obtained from the experimental determined gas-liquid-like critical point of a lysozyme dispersion.…”

Second-order resummed thermodynamic perturbation theory for central-force associating potential: Multi-patch colloidal models

“…Note, that for the model with θ (c) K < 30 • all terms in (18), which include n-particle distribution functions with n ≥ 3 are equal to zero and…”

“…In addition to the hard-sphere interaction hs the particles are interacting via a short-ranged square-well orientationally dependent associative potential ass of the type proposed by Bol, 13 Jackson et al 17 and Kern and Frenkel. 18 The corresponding total pair potential is given by (12) = hs (r) + ass (12),…”

“…[10][11][12] Most often theoretical studies of such colloidal particles are carried out using the models of the type developed by Bol 13 and extended further by Nezbeda and co-workers, [14][15][16] Jackson et al, 17 and Kern and Frenkel. 18 Typically, the model is represented by hard spheres with an orientationally dependent attractive interaction mediated by off-center squarewell or anisotropic square-well sites with angular cutoff (conical sites). In the last few decades a substantial amount of work has been carried out on the theoretical description of the structural and thermodynamic properties of these types of models 17,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] (see also the review papers of Sciortino, 34 Bianchi et al 35 and references therein).…”

How to model the interaction of charged Janus particles

“…de For the simulation of Janus particles in various systems a wide number of models reproducing their anisotropic properties are known. The most straightforward approach is to model the particles as hard spheres and to use a square-well potential that is sensitive to the orientation of the patches, as introduced by Kern and Frenkel [17] . This potential can easily be implemented and is used quite often [10,11,[18][19][20][21][22][23][24] .…”