Effect of triplet attractions on the phase diagram of suspensions of charged colloids

Hynninen, Antti-Pekka; Dijkstra, Marjolein; Roij, René van

doi:10.1088/0953-8984/15/48/014

Cited by 21 publications

(24 citation statements)

References 19 publications

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“…Of these observations (ii) has already been confirmed by Dobnikar et al [3] in the truncated-point Yukawa system, However, whether observations (i) and (iii) are supported by the earlier study cannot be answered since the Lindemann criterion used in [3] is not suited to resolve the relative stability of the BCC and FCC phases. Finally, we like to stress that (i), the instability of the BCC phase, was also found recently in our simulation study where the effect of triplet attractions on the phase diagram of charged colloids was investigated [6]. The effect of many-body interactions on the phase behaviour is a destabilization of the BCC phase, which should be observable in experiments.…”

Section: Discussionsupporting

confidence: 80%

“…Indeed, preliminary free energy calculations with x = 1.77 showed a stable BCC phase at 1/κσ = 0.4. Destabilization of the BCC phase was also found recently in a simulation study that investigated the effect of triplet attractions on the phase diagram of charged colloids as a first-order many-body correction to pairwise additivity [6]. It is also worth mentioning that the fluid-FCC phase boundary above the second triple point follows closely the fluid-BCC phase boundary of the non-truncated Yukawa system.…”

Section: Resultssupporting

confidence: 71%

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Phase diagrams of hard-core repulsive Yukawa particles

Hynninen

Dijkstra²

2003

Phys. Rev. E

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156

229

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Using computer simulations we study the phase behaviour of hard spheres with repulsive Yukawa interactions and with the repulsion set to zero at distances larger than a density-dependent cut-off distance. Earlier studies based on experiments and computer simulations in colloidal suspensions have shown that the effective colloid-colloid pair interaction that takes into account many-body effects resembles closely this truncated Yukawa potential. We present a phase diagram for the truncated Yukawa system by combining Helmholtz free energy calculations and the Kofke integration method. Compared to the non-truncated Yukawa system we observe (i) a radical reduction of the stability of the body centred cubic (BCC) phase, (ii) a wider fluid region due to instability of the face centred cubic (FCC) phase and due to a re-entrant fluid phase and (iii) hardly any shift of the (FCC) melting line when compared with the (BCC) melting line for the full Yukawa potential for sufficiently high salt concentrations, i.e. truncation of the potential does not affect the location of the solid-fluid line but replaces only the BCC phase with the FCC at the melting line. We compare our results with earlier results on the truncated Yukawa potential and with results from simulations where the full many-body Poisson-Boltzmann problem is solved.

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Section: Discussionsupporting

confidence: 80%

Section: Resultssupporting

confidence: 71%

Phase diagrams of hard-core repulsive Yukawa particles

Hynninen

Dijkstra²

2003

Phys. Rev. E

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156

229

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“…This discussion was fueled by theoretical results of attractive three-body interactions 13,14 and experiments that show densitydependent pair interactions 15,16 ͑signaling that the underlying interaction is not pairwise͒. In our earlier work, 23,24 we studied the effect of attractive three-body interactions on the phase behavior of charged colloids and found that they give rise to broad fluidfcc and bcc-fcc coexistence regions. [17][18][19] What remains to be less clear-cut is the effect of the many-body interactions on the phase behavior of charged colloids.…”

Section: Introductionmentioning

confidence: 99%

“…23,24 To this end, we develop an efficient simulation method for the highly asymmetric primitive model. 23,24 To this end, we develop an efficient simulation method for the highly asymmetric primitive model.…”

Section: Introductionmentioning

confidence: 99%

Melting line of charged colloids from primitive model simulations

Hynninen¹,

Dijkstra²

2005

The Journal of Chemical Physics

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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).

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“…Moreover, the presence of triplet attractions also affects the relative stability of fcc and bcc crystals. A brief version of this paper was published elsewhere [28].…”

Section: Introductionmentioning

confidence: 99%

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

2004

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We study numerically the effect of attractive triplet interactions on the phase behavior of suspensions of highly charged colloidal particles at low salinity. In our computer simulations, we employ the pair and triplet potentials that were obtained from a numerical Poisson-Boltzmann study [C. Russ et al., Phys. Rev. E 66, 011402 (2002)]. On the basis of free energy calculations, we determine the phase diagram of an aqueous suspension of identical spheres of diameter = 32 nm and charge Z = 80 as a function of colloid concentration and salinity, both for the purely pairwise additive system and for the system with pair and triplet interactions. The main effect of including the triplet interactions is a destabilization of the body-centered-cubic (bcc) crystal phase in favor of the face-centered-cubic (fcc) crystal phase. As a consequence the phase diagram features the coexistence of a rather dilute fluid with an almost-close-packed fcc phase at low salinity and bcc-fcc coexistence with a big density jump at intermediate salinity. The triplet attractions do not affect the phase behavior at sufficiently high salinity; under these conditions the system is well described by the pairwise potential.

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Effect of triplet attractions on the phase diagram of suspensions of charged colloids

Cited by 21 publications

References 19 publications

Phase diagrams of hard-core repulsive Yukawa particles

Phase diagrams of hard-core repulsive Yukawa particles

Melting line of charged colloids from primitive model simulations

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

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