Glassy Dislocation Dynamics in 2D Colloidal Dimer Crystals

Gerbode, Sharon J.; Agarwal, Umang; Ong, Desmond C.; Liddell, Chekesha M.; Escobedo, Fernando A.; Cohen, Itai

doi:10.1103/physrevlett.105.078301

Cited by 37 publications

(31 citation statements)

References 19 publications

(29 reference statements)

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“…Other consequences of the pairing of monomers into dimers include topological defects [5], a restricted, glassy dislocation motion [6,7], and unusual elastic properties [8]. Similar degenerate phases have also been observed for freely-joined chains of hard spheres [9,10].…”

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confidence: 85%

Degenerate Quasicrystal of Hard Triangular Bipyramids

2011

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We report a degenerate quasicrystal in Monte Carlo simulations of hard triangular bipyramids each composed of two regular tetrahedra sharing a single face. The dodecagonal quasicrystal is similar to that 1 recently reported for hard tetrahedra [Haji-Akbari et al., Nature (London) 462, 773 (2009)] but degenerate in the pairing of tetrahedra, and self-assembles at packing fractions above 54%. This notion of degeneracy differs from the degeneracy of a quasiperiodic random tiling arising through phason flips. Free energy calculations show that a triclinic crystal is preferred at high packing fractions.Hard disks and spheres order into hexagonal and facecentered cubic crystals, respectively, above a certain packing fraction. A more complex phase behavior is observed if the disks or spheres are rigidly bonded into dimers (dumbbells) [1][2][3][4]. A solid phase, disordered in the orientation of dimers while ordered on the monomer level, forms if the distance between monomers within a dimer is roughly the diameter of a monomer. This equilibrium solid phase can be alternatively understood as a random pairing of neighboring monomers within the native monomer crystal. The resulting thermodynamic ensemble of ground states is degenerate and the structure is therefore called a degenerate crystal. As shown by Wojciechowski et al.[1] for hard disks, the entropy associated with the degeneracy exceeds the entropy from excluded volume effects, which by itself is sufficient to drive the crystallization of hard monomers. Other consequences of the pairing of monomers into dimers include topological defects [5], a restricted, glassy dislocation motion [6,7], and unusual elastic properties [8]. Similar degenerate phases have also been observed for freely-joined chains of hard spheres [9,10].Although degenerate crystals can potentially assemble from dimers of hard shapes other than disks and spheres, few examples have been reported. One reason is the competition between degenerate crystals and the liquid crystalline phases frequently observed for particles with large aspect ratios. For example, elongated tetragonal parallelepipeds, which for an aspect ratio of 2:1 can be viewed as dimers of face-sharing cubes, form a degenerate parquet phase at intermediate densities before transforming into a smectic liquid crystal that eventually crystallizes [11]. Another simple dimer is the triangular bipyramid (TBP), which consists of two face-sharing, regular tetrahedra (Fig. 1a). The TBP is the simplest face-transitive bipyramid and the twelfth of the 92 Johnson solids. The lack of inversion symmetry of the TBP, however, makes lattice packings non-optimal [12], and thus it is potentially more interesting as a dimer than dimers of spheres and cubes. Moreover, the recent synthesis of TBP-shaped nanoparticles and colloids [13][14][15][16] relevance. In both of the known ordered phases of hard, regular tetrahedra, each tetrahedron is in almost-perfect face-to-face contact with at least one other tetrahedron. The densest known packing of tetrahedr...

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confidence: 85%

Degenerate Quasicrystal of Hard Triangular Bipyramids

2011

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“…Consequently, the Voronoi analysis (VA) has been used in many MD simulations to analyze dislocation dynamics [47]. By counting the number of polygonal facets having three, four, five and six vertices/edges, the computed Voronoi polyhedron for a particle is translated into a compact signature in this method.…”

Section: Voronoi Analysis (Va)mentioning

confidence: 99%

How to identify dislocations in molecular dynamics simulations?

Wang

Yang

et al. 2014

Sci. China Phys. Mech. Astron.

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Dislocations are of great importance in revealing the underlying mechanisms of deformed solid crystals. With the development of computational facilities and technologies, the observations of dislocations at atomic level through numerical simulations are permitted. Molecular dynamics (MD) simulation suggests itself as a powerful tool for understanding and visualizing the creation of dislocations as well as the evolution of crystal defects. However, the numerical results from the large-scale MD simulations are not very illuminating by themselves and there exist various techniques for analyzing dislocations and the deformed crystal structures. Thus, it is a big challenge for the beginners in this community to choose a proper method to start their investigations. In this review, we summarized and discussed up to twelve existing structure characterization methods in MD simulations of deformed crystal solids. A comprehensive comparison was made between the advantages and disadvantages of these typical techniques. We also examined some of the recent advances in the dynamics of dislocations related to the hydraulic fracturing. It was found that the dislocation emission has a significant effect on the propagation and bifurcation of the crack tip in the hydraulic fracturing.

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“…Although some particles of this kind were known from earlier work by others, previous emphasis was on their assembly or dynamics in the presence of external magnetic field [25][26][27][28][29][30][31] . Here, taking advantage of rapid progress in the synthesis of anisotropic colloids [32][33][34][35][36][37] , we go beyond this to delve into the role of shape and constituent anisotropy. Beyond validating and testing the generality of theoretical and in silico predictions regarding dipolar assembly, these findings shed new light on the design of reconfigurable materials 38 in which large structural transitions can arise from small changes in field strength 39 .…”

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confidence: 99%

Colloidal ribbons and rings from Janus magnetic rods

et al. 2013

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Dipolar particles are fundamental building blocks in nature and technology, yet the effect of particle anisotropy is seldom explored. Here, we fabricate colloidal silica rods coated with a hemicylindrical magnetic layer to satisfy multiple criteria: nearly monodisperse, easily imaged and magnetic interaction that dominates over gravity. We confirm long-predicted features of dipolar assembly and stress the microstructural variety brought about by shape and constituent anisotropy, especially by extrapolating knowledge learned from literal molecules. In this colloidal system, we describe analogies to liquid crystalline deformations with bend, splay and twist; an analogy to cis/trans isomerism in organic molecules, which in our system can be controllably and reversibly switched; and a field-switching methodology to direct single ribbons into not only single but also multiple rings that can subsequently undergo hierarchical self-assembly. We highlight subtle material issues of control and design rules for reconfigurable dipolar materials with building blocks of complex shape.

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Glassy Dislocation Dynamics in 2D Colloidal Dimer Crystals

Cited by 37 publications

References 19 publications

Degenerate Quasicrystal of Hard Triangular Bipyramids

Degenerate Quasicrystal of Hard Triangular Bipyramids

How to identify dislocations in molecular dynamics simulations?

Colloidal ribbons and rings from Janus magnetic rods

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