Interaction between colloidal particles

Advances in Colloid and Interface Science, 2002

SOP Transactions on Applied Physics, 2014

The aim of the present work is the determination of the structure and thermodynamics of a monodisperse colloidal solution. We assume that the interaction potential between colloids is of Yukawa or Sogami types. The former is purely repulsive, while the second, it involves, in addition to a repulsive part, a Van der Waals attractive tail. We compute the structure factor and thermodynamics properties, using, the integral equation one with the hybridized mean spherical approximation. We first compare the results relative to this theory, and with this obtained within Monte Carlo simulation. We show that results from integral equation method with a Sogami potential and those of simulation are in good quantitative agreement. Finally, our theoretical results are compared to those of experiment by Tata and coworkers. We find that integral equation theory with Sogami potential agrees well with experiment.

The Journal of Chemical Physics, 2002

We use an integral equation scheme to obtain self-consistently the effective interaction between colloids in salt-free charged colloidal suspensions. The colloid-counterion direct correlation function (DCF) is obtained for the fixed colloid-colloid pair structure by solving the corresponding hypernetted-chain equation (HNC). This DCF is then used to formulate an effective colloid-colloid pair potential for which the one-component reference hypernetted-chain equation is

Europhysics Letters (EPL), 1998

A simple theory of the fluid state of a charged colloidal suspension is proposed. The full free energy of a polyelectrolyte solution is calculated. It is found that the counterions condense onto the polyions forming clusters composed of one polyion and n counterions. The distribution of cluster sizes is determined explicitly. In agreement with the current experimental and Monte Carlo results, no liquid-gas phase separation was encountered.

Le Journal de Physique IV, 2000

The paper summarizes recent theoretical work on the effective interactions between charge-stabilized, spherical colloidal particles. Despite the purely repulsive nature of the effective pair potential, fluid-fluid phase separation is shown to occur at very low salt concentrations, due to a frequently forgotten "volume" term. A longrange attractive component to the pair interaction is predicted when the colloidal particles are confined by charged surfaces (e.g. in slit or pore geometries), in agreement with recent experimental findings. The importance of excluded volume and solvent effects is briefly discussed.

Physical Review E, 2002

Within nonlinear Poisson-Boltzmann theory we calculate the pair and triplet interactions between charged colloidal spheres, specifically in the nonlinear regime of low salt concentrations and high charges. We find repulsive pair interactions and attractive triplet interactions. Within a van der Waals-like mean-field theory we estimate in which parameter regime a gas-liquid coexistence is to be expected.

Chemistry Letters, 2012

Journal of Physics: Condensed Matter, 2000

We discuss the phase behaviour of suspensions of charged colloidal particles, specifically at low salt concentrations. The total free energy F of a three-component system of charged colloids and positive and negative salt ions can be expressed as F = F DLVO + F 0 , where F DLVO is the free energy of a one-component system of colloidal particles interacting via the DLVO pair potential, and F 0 consists of density-dependent contributions from the salt ions. We argue that F 0 drives a gas-liquid spinodal at low salt concentrations, in accordance with several experimental observations. The underlying mechanism is equivalent to that of the well-established gas-liquid transition in simple electrolytes. The present theory connects directly the classic linearized Poisson-Boltzmann theories for simple electrolytes (Debye-Hückel) and colloidal suspensions (DLVO).

2016

We investigate spherical macroions in the strong Coulomb coupling regime within the primitive model in salt-free environment. We first show that the ground state of an isolated colloid is naturally overcharged by simple electrostatic arguments illustrated by the Gillespie rule. We furthermore demonstrate that in the strong Coulomb coupling this mechanism leads to ionized states and thus to long range attractions between like-charged spheres. We use molecular dynamics simulations to study in detail the counterion distribution for one and two highly charged colloids for the ground state as well as for finite temperatures. We compare our results in terms of a simple version of a Wigner crystal theory and find excellent qualitative and quantitative agreement. PACS numbers: 82.70.Dd, 61.20.Qg, 41.20.-q Typeset using REVTEX ∗email: messina@mpip-mainz.mpg.de †email: holm@mpip-mainz.mpg.de ‡email: k.kremer@mpip-mainz.mpg.de 1

2005

We study the sedimentation equilibrium of low salt suspensions of binary mixtures of charged colloids, both by Monte Carlo simulations of an effective colloids-only system and by Poisson-Boltzmann theory of a colloid-ion mixture. We show that the theoretically predicted lifting and layering effect, which involves the entropy of the screening ions and a spontaneous macroscopic electric field (Zwanikken and van Roij 2005 Europhys. Lett. 71 480), can also be understood on the basis of an effective colloid-only system with pairwise screened-Coulomb interactions. We consider, by theory and by simulation, both repelling like-charged colloids and attracting oppositely charged colloids, and we find a re-entrant lifting and layering phenomenon when the charge ratio of the colloids varies from large positive through zero to large negative values.