Phase equilibria and clustering in size-asymmetric primitive model electrolytes

Yan, Qiliang; Pablo, Juan J. de

doi:10.1063/1.1335653

Cited by 46 publications

(57 citation statements)

References 19 publications

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“…6͒, as proposed for the asymmetric ionic fluids. 29 The effect arises from the difference in the number of interacting pairs of similarly charged colloids in the dilute and dense phases. The internal energy calculated using the MSA for a mixture of Yukawa potentials shows similar trends, with minima moving to higher as the density increases.…”

Section: Resultsmentioning

confidence: 99%

Liquid-gas separation in colloidal electrolytes

Caballero¹,

Puertas²,

Fernández-Barbero³

et al. 2006

The Journal of Chemical Physics

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Articles you may be interested inThe liquid-gas transition of an electroneutral mixture of oppositely charged colloids, studied by Monte Carlo simulations, is found in the low-temperature-low-density region. The critical temperature shows a nonmonotonous behavior as a function of the interaction range, −1 , with a maximum at Ϸ 10, implying an island of coexistence in the -plane. The system is arranged in such a way that each particle is surrounded by shells of particles with alternating charge. In contrast with the electrolyte primitive model, both neutral and charged clusters are obtained in the vapor phase.

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Section: Resultsmentioning

confidence: 99%

Liquid-gas separation in colloidal electrolytes

Caballero¹,

Puertas²,

Fernández-Barbero³

et al. 2006

The Journal of Chemical Physics

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“…The ions on the chain backbone and the counterions can be expected to form multiple clusters with nontrivial dipole and multipole interactions, just as observed previously in the restricted primitive model. [52][53][54][55][56] This type of phenomenon cannot be easily treated by continuum theories since the discrete particle nature of the ions comes into play in an important way. To gain insight into this phenomenon, we show a snapshot of our simulated gel for ␣ = 0.6, ⌫ =3, and = 4.85ϫ 10 −4 , in Fig.…”

Section: Influence Of Counterion Valance On the Counterion Cloudmentioning

confidence: 99%

Molecular simulation of the swelling of polyelectrolyte gels by monovalent and divalent counterions

Yin

Horkay

Douglas

et al. 2008

The Journal of Chemical Physics

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Permanently crosslinked polyelectrolyte gels are known to undergo discontinuous first-order volume phase transitions, the onset of which may be caused by a number of factors. In this study we examine the volumetric properties of such polyelectrolyte gels in relation to the progressive substitution of monovalent counterions by divalent counterions as the gels are equilibrated in solvents of different dielectric qualities. We compare the results of coarse-grained molecular dynamics simulations of polyelectrolyte gels with previous experimental measurements by others on polyacrylate gels. The simulations show that under equilibrium conditions there is an approximate cancellation between the electrostatic contribution and the counterion excluded-volume contribution to the osmotic pressure in the gel-solvent system; these two contributions to the osmotic pressure have, respectively, energetic and entropic origins. The finding of such a cancellation between the two contributions to the osmotic pressure of the gel-solvent system is consistent with experimental observations that the swelling behavior of polyelectrolyte gels can be described by equations of state for neutral gels. Based on these results, we show and explain that a modified form of the FloryHuggins model for nonionic polymer solutions, which accounts for neither electrostatic effects nor counterion excluded-volume effects, fits both experimental and simulated data for polyelectrolyte gels. The Flory-Huggins interaction parameters obtained from regression to the simulation data are characteristic of ideal polymer solutions, whereas the experimentally obtained interaction parameters, particularly that associated with the third virial coefficient, exhibit a significant departure from ideality, leading us to conclude that further enhancements to the simulation model, such as the inclusion of excess salt, the allowance for size asymmetric electrolytes, or the use of a distance-dependent solvent dielectricity model, may be required. Molecular simulations also reveal that the condensation of divalent counterions onto the polyelectrolyte network backbone occurs preferentially over that of monovalent counterions.

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“…For a symmetric 1:1 electrolyte system, for example, recent experiments [1,2,3,4,5] and simulations [6,7,8,9, 10] strongly support three-dimensional Ising-like criticality as the asymptotic behavior. One of the most basic and successful models of ionic fluids is the restricted primitive model (RPM), in which the ions are viewed as equisized hard spheres carrying positive and negative charges of the same magnitude.…”

Section: Introductionmentioning

confidence: 98%

Phase diagrams in the lattice restricted primitive model: From order-disorder to gas-liquid phase transition

Diehl

Panagiotopoulos

2005

Phys. Rev. E

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The phase behavior of the lattice restricted primitive model (RPM) for ionic systems with additional short-range nearest neighbor (nn) repulsive interactions has been studied by grand canonical Monte Carlo simulations. We obtain a rich phase behavior as the nn strength is varied. In particular, the phase diagram is very similar to the continuum RPM model for high nn strength. Specifically, we have found both gas-liquid phase separation, with associated Ising critical point, and first-order liquid-solid transition. We discuss how the line of continuous order-disorder transitions present for the low nn strength changes into the continuum-space behavior as one increases the nn strength and compare our findings with recent theoretical results by Ciach and Stell [Phys. Rev. Lett. 91, 060601 (2003)].

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Phase equilibria and clustering in size-asymmetric primitive model electrolytes

Cited by 46 publications

References 19 publications

Liquid-gas separation in colloidal electrolytes

Liquid-gas separation in colloidal electrolytes

Molecular simulation of the swelling of polyelectrolyte gels by monovalent and divalent counterions

Phase diagrams in the lattice restricted primitive model: From order-disorder to gas-liquid phase transition

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