Melting line of charged colloids from primitive model simulations

Abstract

We develop an efficient simulation method to study suspensions of charged spherical colloids using the primitive model. In this model, the colloids and the co- and counterions are represented by charged hard spheres, whereas the solvent is treated as a dielectric continuum. In order to speed up the simulations, we restrict the positions of the particles to a cubic lattice, which allows precalculation of the Coulombic interactions at the beginning of the simulation. Moreover, we use multiparticle cluster moves that make the Monte Carlo sampling more efficient. The simulations are performed in the semigrand canonical ensemble, where the chemical potential of the salt is fixed. Employing our method, we study a system consisting of colloids carrying a charge of 80 elementary charges and monovalent co- and counterions. At the colloid densities of our interest, we show that lattice effects are negligible for sufficiently fine lattices. We determine the fluid-solid melting line in a packing fraction eta-inverse screening length kappa plane and compare it with the melting line of charged colloids predicted by the Yukawa potential of the Derjaguin-Landau-Verwey-Overbeek theory. We find qualitative agreement with the Yukawa results, and we do not find any effects of many-body interactions. We discuss the difficulties involved in the mapping between the primitive model and the Yukawa model at high colloid packing fractions (eta>0.2).

Hunting mermaids in real space: known knowns, known unknowns and unknown unknowns

“…Figure 2 shows the success of the Yukawa description. The parameters obtained are close to those of the primitive model, developed in computer simulation by Vladimir Lobaskin and Per Linse [69] and here implemented by Antti-Pekka Hynninen for a much higher charge asymmetry between ions and colloids [70,71]. We see that the parameters in the full primitive model case (top line, Fig, 2) is very similar to the value of the Yukawa model (second line down from the top, Fig, 2).…”

Novel kinetic trapping in charged colloidal clusters due to self-induced surface charge organization

“…Instead of the one-component description which integrates out small ions and leads to a Yukawa interaction between two colloids45, the Primitive Model3846 treats small ions and colloids (macroions) on an equal footing. The solvent is treated as a dielectric medium and each ion and colloid interact Coulombically.…”

Equilibrium sedimentation profile of dilute, salt-free charged colloids

“…11 The ions that hinder the displacement of the colloid at its new position are removed and then reinserted into the space left empty by the displacement of the colloid. 11 The ions that hinder the displacement of the colloid at its new position are removed and then reinserted into the space left empty by the displacement of the colloid.…”