Computer simulations of charge and steric stabilised colloidal suspensions

Abstract

Computer simulations of colloidal suspensions are prohibited by slow equilibration as very different length and time scales are involved for the various species. This is the reason that most simulations involve some degree of coarse-graining, whereby the degrees of freedom of the microscopic particles are traced out, and the mesoscopic particles interact with an effective potential, resulting in a coarse-grained, effective one-component description of the suspension. The focus of this paper is on recent simulation work of charge and steric stabilised colloidal suspensions. We discuss both direct simulations of the true colloidal mixture and coarse-grained approaches of the suspension involving effective interactions for the colloids. ᮊ

Effect of three-body interactions on the phase behavior of charge-stabilized colloidal suspensions

“…(14) can be used as a quick tool for mapping out the fluid-fcc and bcc-fcc coexistence points in the lowregime. 1 In Fig. 2 the coexistence points obtained from the free energy curves provided by Eq.…”

“…This suggests that a fully realistic description of charged colloids in this regime requires the inclusion of four-body and higher-order terms as well, which constitutes a daunting task: not only is the calculation of the n-body potential ⍀ ͑n͒ for n ജ 4 computationally demanding, but including them into an (efficient) Monte Carlo scheme is also far from trivial. However, at high salinity the system is well described by pairwise additivity, and therefore we ex- 1 The approximate free energy F approx in Eq. (14) only accounts for the "crude" features of the phase diagram-i.e., either for the broad fluid-fcc or for the broad bcc-fcc phase coexistences.…”

“…A statistical mechanics description of these highly asymmetric multicomponent fluids represents a major challenge as very different length and time scales are involved for the various species. This is the reason why attempts to treat the mesoscopic colloids and the microscopic salt and solvent particles on an equal footing usually fail [1]. It is therefore not surprising that the present understanding of these systems is based on simplified models, in which the degrees of freedom of the microscopic particles have been integrated out, such that the mesoscopic particles interact with an effective (usually pairwise) potential, resulting in a coarse-grained effective onecomponent description of the suspension.…”

A Model for the Stability of a TiO2 Dispersion

“…For the present purposes, I shall consider effec = 100 [18]. The constant is the inverse of the Debye length, which shall be considered to be equal to 20 nm, as in typical aqueous paints [15].…”

Effect of the acrylic acid content on the permeability and water uptake of poly(styrene-co-butyl acrylate) latex films

“…This simple potential is suitable for describing different colloidal features because it takes into account the excluded volume of the colloids [17,18]; however, since colloidal particles have surface charge due to the presence of electrostatic charges, i.e. sulphate groups from the initiator and namely ionized carboxylic groups from the AA, colloidal particles start to repeal each other before they get into contact [19,20]. As the number of surface charges on the particle surface increases, the repulsion between the particles becomes stronger.…”