Anisotropic Pair Correlations and Structure Factors of Confined Hard-Sphere Fluids: An Experimental and Theoretical Study

Nygård, Kim; Kjellander, Roland; Sarman, Sten; Chodankar, Shirish; Perret, Edith; Buitenhuis, Johan; Veen, J. F. van der

doi:10.1103/physrevlett.108.037802

Cited by 55 publications

(73 citation statements)

References 28 publications

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“…Recently, however, methods have become available thanks to a combination of classic liquid-state theory and modern computational power that yields accurate results on practical timescales. We develop here a description of the soft structure between polarizable walls derived from a single theoretical framework, with minimal assumptions, matching the reliability of a Monte Carlo simulation (21)(22)(23), and agreeing with experimental observations (24). This description provides a practical understanding of electrostatic correlations in charged fluids and predictability in experiments.…”

mentioning

confidence: 65%

Tunable soft structure in charged fluids confined by dielectric interfaces

Zwanikken¹,

Cruz

2013

Proc. Natl. Acad. Sci. U.S.A.

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Fluids of charged particles act as the supporting medium for chemical reactions and physical, dynamical, and biological processes. The local structure in an electrolytic background is deformed by micro-and nanoscopic polarizable objects. Vice versa, the forces between the objects are regulated by the cohesive properties of the background. We study here the range and strength of these forces and the microscopic origin from which they emerge. We find the forces to be sensitively dependent on the material properties of the charged fluid and the immersed solutes. The induced interactions can be varied over decades, offering high tunability and aided by accurate theory, control in experiments and applications. To distinguish correlational effects from simple ionic screening, we describe electrolyte-induced forces between neutral objects. The interplay of thermal motion, short-range repulsions, and electrostatic forces is responsible for a soft structure in the fluid. This structure changes near polarizable interfaces and causes diverse attractions between confining walls that seem well-exploited by microbiological systems. For parameters that correspond to monovalent electrolytes in biologically and technologically relevant aqueous environments, we find induced forces between nanoscopic areas of the order of piconewtons over a few nanometers. T he region where different phases meet at an interface hosts the regulatory processes that determine the face of the Earth from a global scale down to the microscopic-length scales. These processes include the chemical reactions in the atmosphere and the Earth's crust at the water-air and water-solid interfaces (1) as well as the highly specific processes in biology that are coordinated by membranes and complex macromolecular agents (2). Interfaces can localize reactive components, mediate interactions, and allow components in different phases to meet in a selective way, offering tunable reaction rates over a vast range of magnitudes. The catalytic qualities of interfaces are broadly exploited in industrial processing that involves an ample variety of applications, such as metal extraction, water purification, phase transfer catalysis, and reprocessing of nuclear waste. In addition to the chemical aspects, interfaces also have distinct physical properties, which find their applications in transistors and supercapacitors as well as emulsion stabilization.In this paper, we highlight the physical properties of the liquidsolid interface, with a strong focus on fluids of charged particles that are confined by two dielectric boundaries. In the theoretical analysis, the charged particles are characterized by the charge q ± and the maximum coupling strength set by an effective hardsphere radius a ± and the Coulomb potential at contact. The solvent is considered implicitly by a constant permittivity « s relative to the vacuum permittivity. By adopting these simplifications that constitute the so-called Primitive Model, we can connect to a tradition of research and expand on familiar kno...

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mentioning

confidence: 65%

Tunable soft structure in charged fluids confined by dielectric interfaces

Zwanikken¹,

Cruz

2013

Proc. Natl. Acad. Sci. U.S.A.

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“…For these large packing fractions the dynamics tends to become very slow. Such a dramatic slowdown of dynamics usually is termed glassy dynamics and its relation to structure is the subject of intensive research [16,19,75,[80][81][82][83][84][85][86]. Advanced theories that deal with glassy dynamics, e.g., mode coupling theory [81,83], its generalization [86], and similar approaches [80,82,85], rely on the knowledge of the structure of the system.…”

Section: Discussionmentioning

confidence: 99%

Anisotropic pair correlations in binary and multicomponent hard-sphere mixtures in the vicinity of a hard wall: A combined density functional theory and simulation study

2015

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The fundamental measure approach to classical density functional theory has been shown to be a powerful tool to predict various thermodynamic properties of hard-sphere systems. We employ this approach to determine not only one-particle densities but also two-particle correlations in binary and six-component mixtures of hard spheres in the vicinity of a hard wall. The broken isotropy enables us to carefully test a large variety of theoretically predicted two-particle features by quantitatively comparing them to the results of Brownian dynamics simulations. Specifically, we determine and compare the one-particle density, the total correlation functions, their contact values, and the force distributions acting on a particle. For this purpose, we follow the compressibility route and theoretically calculate the direct correlation functions by taking functional derivatives. We usually observe an excellent agreement between theory and simulations, except for small deviations in cases where local crystal-like order sets in. Our results set the course for further investigations on the consistency of functionals as well as for structural analysis on, e.g., the primitive model. In addition, we demonstrate that due to the suppression of local crystallization, the predictions of six-component mixtures are better than those in bidisperse or monodisperse systems. Finally, we are confident that our results of the structural modulations induced by the wall lead to a deeper understanding of ordering in anisotropic systems in general, the onset of heterogeneous crystallization, caging effects and glassy dynamics close to a wall, as well as structural properties in systems with confinement.

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“…Examples range from liquid supply, adhesion to lubrication, friction in narrow channels as well as in biological systems. Confinement effects for densely-packed liquids have been investigated in slit geometry mainly by computer simulations [104,105] and experiments [106,107] focusing on the regime of moderate confinement with slit widths of several particle diameters or larger. These studies revealed the existence of an oscillatory density profile close to the wall [106].…”

Section: Confined Liquidsmentioning

confidence: 99%

Complex dynamics induced by strong confinement – From tracer diffusion in strongly heterogeneous media to glassy relaxation of dense fluids in narrow slits

Mandal

Spanner-Denzer

Leitmann

et al. 2017

Eur. Phys. J. Spec. Top.

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Abstract. We provide an overview of recent advances of the complex dynamics of particles in strong confinements. The first paradigm is the Lorentz model where tracers explore a quenched disordered host structure. Such systems naturally occur as limiting cases of binary glassforming systems if the dynamics of one component is much faster than the other. For a certain critical density of the host structure the tracers undergo a localization transition which constitutes a critical phenomenon. A series of predictions in the vicinity of the transition have been elaborated and tested versus computer simulations. Analytical progress is achieved for small obstacle densities. The second paradigm is a dense strongly interacting liquid confined to a narrow slab. Then the glass transition depends nonmonotonically on the separation of the plates due to an interplay of local packing and layering. Very small slab widths allow to address certain features of the statics and dynamics analytically.

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Anisotropic Pair Correlations and Structure Factors of Confined Hard-Sphere Fluids: An Experimental and Theoretical Study

Cited by 55 publications

References 28 publications

Tunable soft structure in charged fluids confined by dielectric interfaces

Tunable soft structure in charged fluids confined by dielectric interfaces

Anisotropic pair correlations in binary and multicomponent hard-sphere mixtures in the vicinity of a hard wall: A combined density functional theory and simulation study

Complex dynamics induced by strong confinement – From tracer diffusion in strongly heterogeneous media to glassy relaxation of dense fluids in narrow slits

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