Many-body effects for critical Casimir forces

Mattos, Thiago Gomes de; Harnau, Ludger; Dietrich, S.

doi:10.1063/1.4791554

Cited by 35 publications

(43 citation statements)

References 46 publications

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“…They have observed that many-body effects become rather significant as the solvent is brought thermodynamically close to a critical point. They have also found that many-body effects tgmattos@des.cefetmg.br tend to decrease the net attraction between colloids, which contrasts with previous results from mean-field calculations lor a system ol two spherical colloids facing a planar homogeneous substrate [51], In the latter case it was shown that many-body effects due to the presence of a substrate do not exhibit a uniform trend but can either increase or decrease the net attraction between colloids. In order to deepen the understanding of many-body effects concerning critical Casimir interactions we consider a system of three colloidal particles under the influence of CCFs.…”

Section: Introductionmentioning

confidence: 77%

Three-body critical Casimir forces

2015

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Within mean-field theory we calculate universal scaling functions associated with critical Casimir forces for a system consisting of three parallel cylindrical colloids immersed in a near-critical binary liquid mixture. For several geometrical arrangements and boundary conditions at the surfaces of the colloids we study the force between two colloidal particles in the direction normal to their axes, analyzing the influence of the presence of a third particle on that force. Upon changing temperature or the relative positions of the particles we observe interesting features such as a change of sign of this force caused by the presence of the third particle. We determine the three-body component of the forces acting on one of the colloids by subtracting the pairwise forces from the total force. The three-body contribution to the total critical Casimir force turns out to be more pronounced for small surface-to-surface distances between the colloids as well as for temperatures close to criticality. Moreover, we compare our results with similar ones for other physical systems such as three atoms interacting via van der Waals forces.

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Section: Introductionmentioning

confidence: 77%

Three-body critical Casimir forces

2015

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“…39 We conclude that the longer range of the interaction at similar interaction magnitude makes many-body effects more pronounced at the critical solvent composition, in agreement with recent mean field estimates of many-body critical Casimir forces in a system of two colloids near a wall. 40 We note, however, that for the few colloid-colloid-wall configurations investigated in that study, many-body forces often increased rather than decreased the colloid-colloid attraction. The downward shift of the calculated gas-liquid curve relative to the experimental data observed here suggests that many-body forces in systems of many colloids decrease the net attractive force between the colloids.…”

Section: A Phase Diagrammentioning

confidence: 91%

Temperature-sensitive colloidal phase behavior induced by critical Casimir forces

Dang

Verde

Nguyen

et al. 2013

The Journal of Chemical Physics

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We report Monte Carlo simulations of phase behavior of colloidal suspensions with near-critical binary solvents using effective pair potentials from experiments. At off-critical solvent composition, the calculated phase diagram agrees well with measurements of the experimental system, indicating that many-body effects are limited. Close to the critical composition, however, agreement between experiment and simulation becomes poorer, signaling the increased importance of many-body effects. Both at and off the critical solvent concentration, the colloidal phase diagram is qualitatively similar to those of molecular systems and obeys the principle of corresponding states with one striking difference: it occurs in a narrow temperature interval of <1 • C below the solvent phase separation temperature.

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“…As far as the theoretical side is concerned, it was de Gennes who first obtained the CCF between spherical particles [53] considering a local freeenergy functional. Among the other techniques used to study the CCF in sphere-plate and sphere-sphere geometries are the Ornstein-Zernike theory [54], conformal invariance methods [55][56][57], Monte Carlo calculations [58][59][60][61][62][63][64][65][66][67], fluid-particle dynamics simulations [68,69], mean-field type [70][71][72][73][74] and density-functional [75] theory calculations combined with the Derjaguin approximation [44,[76][77][78]. Several review articles and works [8,[79][80][81][82] summarize both the experimental and theoretical results presented there.…”

Section: Introductionmentioning

confidence: 99%

Sign change in the net force in sphere-plate and sphere-sphere systems immersed in nonpolar critical fluid due to the interplay between the critical Casimir and dispersion van der Waals forces

Valchev

Dantchev

2017

Phys. Rev. E

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We study systems in which both long-ranged van der Waals and critical Casimir interactions are present. The last arise as an effective force between bodies when immersed in a near-critical medium, say a nonpolar onecomponent fluid or a binary liquid mixture. They are due to the fact that the presence of the bodies modifies the order parameter profile of the medium between them as well as the spectrum of its allowed fluctuations. We study the interplay between these forces, as well as the total force (TF) between a spherical colloid particle and a thick planar slab, and between two spherical colloid particles. We do that using general scaling arguments and mean-field type calculations utilizing the Derjaguin and the surface integration approaches. They both are based on data of the forces between two parallel slabs separated at a distance L from each other, confining the fluctuating fluid medium characterized by its temperature T and chemical potential µ. The surfaces of the colloid particles and the slab are coated by thin layers exerting strong preference to the liquid phase of the fluid, or one of the components of the mixture, modeled by strong adsorbing local surface potentials, ensuring the socalled (+, +) boundary conditions. On the other hand, the core region of the slab and the particles, influence the fluid by long-ranged competing dispersion potentials. We demonstrate that for a suitable set of colloids-fluid, slab-fluid, and fluid-fluid coupling parameters the competition between the effects due to the coatings and the core regions of the objects involved result, when one changes T , µ or L, in sign change of the Casimir force (CF) and the TF acting between the colloid and the slab, as well as between the colloids. This can be used for governing the behavior of objects, say colloidal particles, at small distances, say in colloid suspensions for preventing flocculation. It can also provide a strategy for solving problems with handling, feeding, trapping and fixing of microparts in nanotechnology. Data for specific substances in support of the experimental feasibility of the theoretically predicted behavior of the CF and TF have been also presented.

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Many-body effects for critical Casimir forces

Cited by 35 publications

References 46 publications

Three-body critical Casimir forces

Three-body critical Casimir forces

Temperature-sensitive colloidal phase behavior induced by critical Casimir forces

Sign change in the net force in sphere-plate and sphere-sphere systems immersed in nonpolar critical fluid due to the interplay between the critical Casimir and dispersion van der Waals forces

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