Lack of long-range order in confined two-dimensional model colloidal crystals

Ricci, Andrea; Nielaba, Peter; Sengupta, Surajit; Binder, Kurt

doi:10.1103/physreve.74.010404

Cited by 26 publications

(45 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…efficient r −12 potential with a cutoff (in order to make it strictly short ranged), a shift (in order to ensure that it ends with a value of zero), and a smoothing factor (to make it differentiable). A further motivation to use this model potential is that it is essentially the same potential used in the studies of confinement effects on colloidal crystals without shear [25][26][27][28][29][30] and of two-dimensional melting [44]. This potential is defined as [41,42] …”

Section: Details Of the Simulationmentioning

confidence: 99%

Langevin dynamics simulations of a two-dimensional colloidal crystal under confinement and shear

et al. 2012

Self Cite

View full text Add to dashboard Cite

Langevin dynamics simulations are used to study the effect of shear on a two-dimensional colloidal crystal (with implicit solvent) confined by structured parallel walls. When walls are sheared very slowly, only two or three crystalline layers next to the walls move along with them, while the inner layers of the crystal are only slightly tilted. At higher shear velocities, this inner part of the crystal breaks into several pieces with different orientations. The velocity profile across the slit is reminiscent of shear banding in flowing soft materials, where liquid and solid regions coexist; the difference, however, is that in the latter case the solid regions are glassy while here they are crystalline. At even higher shear velocities, the effect of the shearing becomes smaller again. Also the effective temperature near the walls (deduced from the velocity distributions of the particles) decreases again when the wall velocity gets very large. When the walls are placed closer together, thereby introducing an incommensurability between the periodicity of the confined crystal and the walls, a structure containing a soliton staircase arises in simulations without shear. Introducing shear increases the disorder in these systems until no solitons are visible anymore. Instead, similar structures like in the case without mismatch result. At high shear rates, configurations where the incommensurability of the crystalline structure is compensated by the creation of holes become relevant.

show abstract

Section: Details Of the Simulationmentioning

confidence: 99%

Langevin dynamics simulations of a two-dimensional colloidal crystal under confinement and shear

et al. 2012

Self Cite

View full text Add to dashboard Cite

show abstract

“…The main focus of this discussion will be on the phenomenon of layer reduction. Layering of particles in 2D systems due to the presence of walls is well known for equilibrium systems [12,13].…”

mentioning

confidence: 99%

Layer Reduction in Driven 2D-Colloidal Systems through Microchannels

et al. 2006

Self Cite

View full text Add to dashboard Cite

The transport behavior of a system of gravitationally driven superparamagnetic colloidal particles is investigated. The motion of the particles through a narrow channel is governed by magnetic dipole interactions, and a layered structure forms parallel to the walls. The arrangement of the particles is perturbed by diffusion and the motion induced by gravity leading to a density gradient along the channel. Our main result is the reduction of the number of layers. Experiments and Brownian dynamics simulations show that this occurs due to the density gradient along the channel. DOI: 10.1103/PhysRevLett.97.208302 PACS numbers: 82.70.Dd, 61.72.ÿy, 64.60.Cn, 75.40.Mg Lattice defects can be introduced in perfectly ordered crystals by deformations due to external forces. Despite their importance, the dynamical behavior of single dislocations is still rather poorly understood, because they are difficult to generate and observe on the atomic scale. Therefore, the observation of this behavior in a model system will lead to insights that can be transferred to a broad range of systems. Studies of isolated lattice defects have recently become possible in static systems of colloidal crystals [1]. Experiments on the behavior of such defects in a nonequilibrium system can lead to a better understanding of the transport behavior of a wide range of systems.In biological systems, the transport of interacting particles through narrow constrictions is of high importance for many processes, for example, for the size selectivity of transport in ion channels [2]. The complexity of such systems allows one to only make hypotheses on the underlying physics governing such phenomena. Model systems that can be easily accessed experimentally can reveal many of the underlying processes [3]. This requires studies of particle transport through channels with variously shaped walls. In order to perform these studies, transport through channels with straight walls has to be well understood in experiments shown in this Letter.In this work, we report on studies of the transport behavior of colloids in a quasi-two-dimensional (2D) setup. The colloids are superparamagnetic; therefore, the interaction energy can be continuously tuned by the application of an external magnetic field [4]. The particles are driven by gravity through a narrow constriction (channel). Such driven diffusive systems serve as model systems for theoretical studies of nonequilibrium behavior [5]. In addition, such a system resembles the classical case of a quantum point contact in mesoscopic electronics [6,7] or in metallic single atom contacts [8,9]. These contacts exhibit transport in electronic channels due to quantization effects. These quantum channels can be seen as analogous to the layers in the macroscopic transport, since both occur due to the interaction of the particles with the confining potential. A classical version of a similar scenario can be built on a liquid helium surface, which is loaded with charges. For such a system, the formation of layers has been repor...

show abstract

“…It is expected that for macroscopically large solids these fluctuations would reduce to the random nucleation of steps on the solid surface and the sort of coherence observed here would be absent. Confining a thin 'long' strip of solid by smooth walls in quasi one dimension leads, strictly speaking, to a destruction of solid-like order [20,35] and an enhancement of smectic-like ordering of individual layers parallel to the confining walls. It is this reduction of interlayer coupling which is ultimately responsible for the spallation of single solid layers.…”

Section: Discussionmentioning

confidence: 99%

“…This difference comes about because unlike a bulk system, a strained nanocrystal on the verge of a transition from a metastable n + 1 to a n layered state readily absorbs kinetic energy from the pulse. Also, as mentioned before, a confined solid strip in two-dimensions has very strong smectic ordering which effectively decreases the coupling between the layers [20,35]. In fact, a quasi onedimensional solid (L x ≫ L s ) is better regarded as a smectic with weak solid like modulations.…”

Section: Mass and Momentum Transfermentioning

confidence: 98%

Fluctuations at a constrained liquid-solid interface

Chaudhuri

Sengupta

2007

Phys. Rev. E

View full text Add to dashboard Cite

We study the interface between a solid trapped within a bath of liquid by a suitably shaped non-uniform external potential. Such a potential may be constructed using lasers, external electric or magnetic fields or a surface template. We study a two dimensional case where a thin strip of solid, created in this way, is surrounded on either side by a bath of liquid with which it can easily exchange particles. Since height fluctuations of the interface cost energy, this interface is constrained to remain flat at all length scales. However, when such a solid is stressed by altering the depth of the potential; beyond a certain limit, it responds by relieving stress by novel interfacial fluctuations which involve addition or deletion of entire lattice layers of the crystal. This "layering" transition is a generic feature of the system regardless of the details of the interaction potential. We show how such interfacial fluctuations influence mass, momentum and energy transport across the interface. Tiny momentum impulses produce weak shock waves which travel through the interface and cause the spallation of crystal layers into the liquid. Kinetic and energetic constraints prevent spallation of partial layers from the crystal, a fact which may be of some practical use. We also study heat transport through the liquid-solid interface and obtain the resistances in liquid, solid and interfacial regions (Kapitza resistance) as the solid undergoes such layering transitions. Heat conduction, which shows strong signatures of the structural transformations, can be understood using a free volume calculation.

show abstract

Lack of long-range order in confined two-dimensional model colloidal crystals

Cited by 26 publications

References 43 publications

Langevin dynamics simulations of a two-dimensional colloidal crystal under confinement and shear

Langevin dynamics simulations of a two-dimensional colloidal crystal under confinement and shear

Layer Reduction in Driven 2D-Colloidal Systems through Microchannels

Fluctuations at a constrained liquid-solid interface

Contact Info

Product

Resources

About