Nonadditivity in the effective interactions of binary charged colloidal suspensions

Allahyarov, Elshad; Löwen, Hartmut

doi:10.1088/0953-8984/21/42/424117

Cited by 23 publications

(22 citation statements)

References 69 publications

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“…We observe that the simulation data reproduce a Yukawa-like functionality in all cases, at least at short and moderate distances. This result is consistent with the findings of Amico and Löwen 35 and Allahyarov and Löwen, 36 who also predict Yukawa-like interactions from molecular dynamics and Monte Carlo simulations. This is also consistent with the theoretical prediction about the validity of a mean field approximation, such as the PB theory, when the parameter 2 B…”

Section: Resultssupporting

confidence: 92%

Internal and free energy in a pair of like-charged colloids: Monte Carlo simulations

Cuetos

Anta

Puertas

2010

The Journal of Chemical Physics

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The effective interaction between two colloidal particles in a bath of monovalent co- and counterions is studied by means of lattice Monte Carlo simulations with the primitive model. The internal electrostatic energy as a function of the colloid distance is studied fixing the position of the colloids. The free energy of the whole system is obtained introducing a bias parabolic potential, that allows us to sample efficiently small separations between the colloidal particles. For small charges, both the internal and free energy increase when the colloids approach each other, resulting in an effective repulsion driven by the electrostatic repulsion. When the colloidal charge is large enough, on the other hand, the colloid-ion coupling is strong enough to form double layers. The internal energy in this case decreases upon approaching the colloids because more ions enter the double layer. This attractive contribution to the interaction between the colloids is stronger for larger charges and larger ionic concentrations. However, the total free energy increases due to the loss of ionic entropy, and resulting finally in a repulsive interaction potential driven by the entropic contributions. The loss of ionic entropy can be almost quantitatively reproduced with the ideal contribution, the same level of approximation as the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The overall behavior is captured by the DLVO theory qualitatively, and a comparison is made with the functional form predicted by the theory, showing moderate agreement.

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Section: Resultssupporting

confidence: 92%

Internal and free energy in a pair of like-charged colloids: Monte Carlo simulations

Cuetos

Anta

Puertas

2010

The Journal of Chemical Physics

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“…The non-additivity parameter ∆ y can in general be either positive or negative. Recent primitive model simulations 6 of the mean force between charged colloids have identified surprisingly large non-zero values of non-additivity, although to-date experimental evidence for non-additivity in charged systems is absent. Accordingly, an important open question is to what extent are the pair interactions between charged micro-and nano-particles in real systems non-additive?…”

Section: Introductionmentioning

confidence: 99%

Non-additivity of pair interactions in charged colloids

Finlayson

Bartlett

2016

The Journal of Chemical Physics

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It is general wisdom that the pair potential of charged colloids in a liquid may be closely approximated by a Yukawa interaction, as predicted by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. We experimentally determine the effective forces in a binary mixture of like-charged particles, of species 1 and 2, with blinking optical tweezers. The measured forces are consistent with a Yukawa pair potential but the (12) cross-interaction is not equal to the geometric mean of the (11) and (22) like-interactions, as expected from DLVO. The deviation is a function of the electrostatic screening length and the size ratio, with the cross-interaction measured being consistently weaker than DLVO predictions. The corresponding non-additivity parameter is negative and grows in magnitude with increased size asymmetry.

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“…Integrating out microion degrees of freedom from the partition function, assuming linear response of microion densities to macroion electrostatic potentials, and making a mean field approximation for the microion response functions, we obtain effective pair potential energies between macroion species m and n of the form v mn,eff (r) = A mn exp(−κr) r , r > a m + a n , where κ is the inverse Debye screening length and the prefactors A mn depend on macroion sizes and charges. Equation (5) is the well-known Yukawa effective pair potential assumed in many simulation studies [11,75,76]. In addition to confirming the general form of the effective pair potentials, however, our approach also incorporates macroion excluded volume into the screening constant and yields a one-body volume energy, which depends on the bulk densities of all microions (both salt ions and counterions).…”

Section: Linear Response Theorymentioning

confidence: 82%

Effective electrostatic interactions in mixtures of charged colloids

Chung

Denton

2013

Phys. Rev. E

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We present a theory of effective electrostatic interactions in polydisperse suspensions of charged macroions, generalizing to mixtures a theory previously developed for monodisperse suspensions. Combining linear response theory with a random phase approximation for microion correlations, we coarse grain the microion degrees of freedom to derive general expressions for effective macroion-macroion pair potentials and a one-body volume energy. For model mixtures of charged hard-sphere colloids, we give explicit analytical expressions. The resulting effective pair potentials have the same general form as predicted by linearized Poisson-Boltzmann theory, but consistently incorporate dependence on macroion density and excluded volume via the Debye screening constant. The volume energy, which depends on the average macroion density, contributes to the free energy and so can influence thermodynamic properties of deionized suspensions. To validate the theory, we compute radial distribution functions of binary mixtures of oppositely charged colloidal macroions from molecular dynamics simulations of the coarse-grained model (with implicit microions), taking effective pair potentials as input. Our results agree closely with corresponding results from more computationally intensive Monte Carlo simulations of the primitive model (with explicit microions). Simulations of a mixture with large size and charge asymmetries indicate that charged nanoparticles can enhance electrostatic screening of charged colloids. The theory presented here lays a foundation for future large-scale modeling of complex mixtures of charged colloids, nanoparticles, and polyelectrolytes.

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Nonadditivity in the effective interactions of binary charged colloidal suspensions

Cited by 23 publications

References 69 publications

Internal and free energy in a pair of like-charged colloids: Monte Carlo simulations

Internal and free energy in a pair of like-charged colloids: Monte Carlo simulations

Non-additivity of pair interactions in charged colloids

Effective electrostatic interactions in mixtures of charged colloids

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