Free-expansion melting of two dimensional colloidal crystals

Tang, Yeke; Armstrong, A. J.; Mockler, R. C.; O'Sullivan, W.J.

doi:10.1080/01411599008206884

Cited by 12 publications

(6 citation statements)

References 15 publications

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“…Note that, as in Ref. [82,83], there is quite a lot of 6-fold order even in the liquid phase, not too far from the hexatic-liquid transition, with approximately 80% of the particles being of this kind.…”

Section: A Number Densitiessupporting

confidence: 59%

“…The density of free dislocations is compatible with the KTHNY criticality with ν = 0.37 while there is no quantitative analysis of the density of free disclinations. Other experimental papers, like the ones by Tang et al [82,83], report the appearance of dislocation loops and complex clusters in the free expansion melting of 2D charged colloidal micro-spheres and cast some doubt on the hexatic-liquid transition being solely driven by the dissociation of dislocations.…”

Section: A Contextmentioning

confidence: 99%

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Unified analysis of Topological Defects in 2D systems of Active and Passive disks

Digregorio¹,

Levis²,

Cugliandolo³

et al. 2021

Preprint

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We provide a comprehensive quantitative analysis of localized and extended topological defects in the steady state of 2D passive and active repulsive Brownian disk systems. We show that, both in and out-of-equilibrium, the passage from the solid to the hexatic is driven by the unbinding of dislocations, in quantitative agreement with the KTHNY singularity. Instead, although disclinations dissociate as soon as the liquid phase appears, extended clusters of defects largely dominate below the solid-hexatic critical line. The latter percolate in the liquid phase very close to the hexaticliquid transition, both for continuous and discontinuous transitions, in the homogeneous liquid regime. At critical percolation the clusters of defects are fractal with statistical and geometric properties that, within our numerical accuracy, are independent of the activity and compatible with the universality class of uncorrelated critical percolation. We also characterize the spatial organization of different kinds of point-like defects and we show that the disclinations are not free, but rather always very near more complex defect structures. At high activity, the bulk of the dense phase generated by Motility-Induced Phase Separation is characterized by a density of point-like defects, and statistics and morphology of defect clusters, set by the amount of activity and not the packing fraction. Hexatic domains within the dense phase are separated by grain-boundaries along which a finite network of topological defects resides, interrupted by gas bubbles in cavitation. The fractal dimension of this network diminishes for increasing activity. This structure is dynamic in the sense that the defect network allows for an unzipping mechanism that leaves free space for gas bubbles to appear, close, and even be released into the dilute phase.

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Section: A Number Densitiessupporting

confidence: 59%

Section: A Contextmentioning

confidence: 99%

Unified analysis of Topological Defects in 2D systems of Active and Passive disks

Digregorio¹,

Levis²,

Cugliandolo³

et al. 2021

Preprint

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“…In addition, it is difficult to distinguish between weak first‐order and continuous transitions; they can be better identified from the free energy jump and van der Waals loop in the equation of state, which can be measured in simulation but is difficult to obtain experimentally. These challenges hinder the testing of the KTHNY scenario in some pioneer colloidal 2D melting experiments, especially for short‐range repulsive particles such as hard disks.…”

Section: D Meltingmentioning

confidence: 99%

Melting of Colloidal Crystals

Wang

Zhou

Han

2016

Adv Funct Materials

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8903wileyonlinelibrary.com ClassificationCrystal melting can be categorized into two types: homogeneous melting in which the melting is equally likely to occur anywhere in the crystal, and heterogeneous melting in which the melting is more likely to occur at the surfaces and defects than the defectfree regions. Heterogeneous melting can be divided into surface melting from a free surface (i.e., the solid-vapor interface), interfacial melting from the interface of two materials (e.g., a crystal and its substrate), grain-boundary melting and melting at weaker defects such as dislocations and vacancies. Homogeneous melting exists in defect-free crystals whose surface melting is suppressed. This type of melting is of theoretical importance but is difficult to achieve experimentally because most crystals melt from surfaces and are not defect-free, which leads to heterogeneous melting. However, homogeneous melting can be conveniently studied by simulation using defect-free crystals under periodic boundary conditions.In heterogeneous melting, particles at the surfaces or defects usually have a higher free energy than those in a perfect crystal. If the free energy is high enough, melting can take place even before the melting point is reached, which is known as premelting. If none of the surfaces and defects has a high enough free energy, then the crystal can be superheated to form a metastable crystal above the bulk melting point. The bulk melting point is the point at which the solid and liquid phases share the same chemical potential, and surfaces are negligible at the thermodynamic limit, i.e., the crystals are infinitely large. For 3D crystals, the likelihood of inducing melting in decreasing order is roughly as follows: 0D corners and 1D edges (intersection of three or two free surfaces) > 1D surface grain boundaries (intersection of a free surface and a bulk grain boundary) > free surfaces > bulk triple junctions > high-angle grain boundaries > the interface between two solids (e.g., on a flat substrate) > lowangle grain boundaries > dislocations > partial dislocations > vacancies > interstitials. [4] Melting starts from the strongest defects and spreads rapidly into the crystal, and thus usually preempts the melting from other weaker defects. Note that this order may not always hold. For example, the energy of free surfaces and grain boundaries varies with their orientations and the interfacial energy at the substrate depends on the affinity between the two solids. Consequently, most free surfaces, some grain boundaries and some solid interfaces will premelt below the bulk melting point T m , while other solid interfaces and grain boundaries and a few free surfaces will only induce melting above T m , i.e., they can be superheated.Crystal melting is affected by many factors such as defects, surfaces, dimensionality, lattice structure, and particle interaction, and thus exhibits rich phenomenology. It is usually a first-order phase transition which currently lacks a fundamental theory. Despite numerous studies ove...

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“…Water [4,5,6,7,8] In the,_e experiments two separate systems were studied as they were slowly compres_d or expanded between the fluid and crystalline phases. [7,8,10,11,12] In this experiment the free expansion melting of two different crystalline samples of as if both surfaces were perfectly smooth. As the plates were brought closer together, to about 1.5 vm, the spheres cane into register with the square array and the channeled arrays as well.…”

Section: A Freezing/melting Transition Of a Colloidal Monolayer On mentioning

confidence: 99%

“…(The form and technique is described in Section 1 and references [7,11,12]). u(r) is the pair potential energy and is required explicitly only for the pressure equation.…”

Section: B the Directmentioning

confidence: 99%

Studies of melting, crystallization, and commensurate-incommensurate transitions in two dimensions

Mockler¹,

O'Sullivan²

1990

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This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific comrncrcial pr_luct, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendatio,n, or favoring by the United States Government or any agency thereof. The views and opimons of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

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Free-expansion melting of two dimensional colloidal crystals

Cited by 12 publications

References 15 publications

Unified analysis of Topological Defects in 2D systems of Active and Passive disks

Unified analysis of Topological Defects in 2D systems of Active and Passive disks

Melting of Colloidal Crystals

Studies of melting, crystallization, and commensurate-incommensurate transitions in two dimensions

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