Degenerate crystals from colloidal dimers under confinement

Muangnapoh, Kullachate; Avendaño, Carlos; Escobedo, Fernando A.; Watson, Chekesha M. Liddell

doi:10.1039/c4sm01895h

Cited by 15 publications

(12 citation statements)

References 46 publications

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“…Crystals formed by CSCs of χ * 0.6 are denoted B1 P and B2 P as the dimers resemble prolate spheroids or dumbbells. Such a comparison draws on similarities between the B2 P crystal and the structures observed in for hard ellipsoids by Dovev et al 84 and by Pfleiderer et al 85 , and although it has not been studied here there may exist another B P crystal where dimer bonds are formed randomly akin to the aperiodic crystal structure formed by dumbbells 29,31,86,87 . The next dimer-based crystal is B PC has similar structure to PC where in this case particles forming dimers can rotate cooperatively.…”

Section: Bulk Phase Behaviour Of Convex Spherical Capsmentioning

confidence: 99%

“…A variety of shapes in bulk and under the influence of external fields have been explored including spherocylinders [15][16][17][18] , cut-spheres 23 [24][25][26][27][28] , dimers [29][30][31] , bowl-like particles [32][33][34] , concave spherical caps [35][36][37] , polyhedra [38][39][40][41][42] , and a variety of branched particles [43][44][45][46] , just to mention few examples. An assumption behind these studies is that the effect of gravitational forces is negligible, corresponding to a situation of colloidal particles embedded within a density matched (implicit) medium.…”

Section: Introductionmentioning

confidence: 99%

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Phase behaviour and gravity-directed self assembly of hard convex spherical caps

McBride

Avendaño

2017

Soft Matter

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We investigate the phase behaviour and self-assembly of convex spherical caps using Monte Carlo simulations. This model is used to represent the main features observed in experimental colloidal particles with mushroom-cap shape [Riley et al., Langmuir, 2010, 26, 1648. The geometry of this non-centrosymmetric convex model is fully characterized by the aspect ratio χ * defined as the spherical cap height to diameter ratio. We use NPT Monte Carlo simulations combined with free energy calculations to determine the most stable crystal structures and the phase behaviour of convex spherical caps with different aspect ratios. We find a variety of crystal structures at each aspect ratio, including plastic and dimer-based crystals; small differences in chemical potential between the structures with similar morphology suggest that convex spherical caps have the tendency to form polycrystalline phases rather than crystallising into a single uniform structure. With the exception of plastic crystals observed at large aspect ratios (χ * > 0.75), crystallisation kinetics seem to be too slow, hindering the spontaneous formation of ordered structures. As an alternative, we also present a study of directing the self-assembly of convex spherical caps via sedimentation onto solid substrates. This study contributes to show how small changes to particle shape can significantly alter the self-assembly of crystal structures, and how a simple gravity field and a template can substantially enhance the process.

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Section: Bulk Phase Behaviour Of Convex Spherical Capsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Phase behaviour and gravity-directed self assembly of hard convex spherical caps

McBride

Avendaño

2017

Soft Matter

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“…Non-spherical particles confined in narrow planar slits are found to exhibit the formation of a variety of structures with symmetries not observed under bulk conditions [34][35][36][37][38][39][40][41][42].…”

Section: Introductionmentioning

confidence: 99%

Nanorings in planar confinement: the role of repulsive surfaces on the formation of lacuna smectics

2018

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We study the structure and liquid-crystalline phase behaviour of a model of confined non-convex circular soft-repulsive nanorings in a planar slit geometry using molecular-dynamics simulation. The separation distance between the structureless parallel soft-repulsive walls is made large enough to allow for the formation of a distinct bulk phase in the central region of the box which is in coexistence with the adsorbed fluid thus allowing the analysis of single-wall effects. As the density of the particles is increased, the fluid adsorbs (wets) onto the planar surfaces leading to the formation of well-defined smectic-A layers with a spacing proportional to the diameter of the rings. An analysis of the nematic order parameter at distances perpendicular to the surface reveals that the particles in each layer exhibit anti-nematic behaviour and planar (edge-on) anchoring relative to the short symmetry axis of the rings. This behaviour is in stark contrast to the behaviour observed in convex disc-like particles that have the tendency to form nematic (discotic) structures with homeotropic (face-on) anchoring. The smectic phases formed by nanorings in the bulk and under confinement are characterised by the formation of low-density layered liquid-crystalline states with large voids, referred to here as lacuna smectic phases. In contrast to what is typically found for confined liquidcrystalline systems involving convex particles, no apparent biaxiality is found for nanorings in planar confinement. We argue that formation of the low-density lacuna smectic layers with planar anchoring is a consequence of the non-convex shape of the circular rings that allow for interpenetration between the particles as observed for nanorings under bulk conditions [C. Avendaño, G.

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“…However, the configurational degeneracy arising from the large number of possible arrangements of the particle bonds within the crystal lattice promotes the formation of aperiodic crystals 63,64 . This crystals have been observed in both two and three dimensional systems in the bulk 58,65 , and under strong geometrical confinement 66 . Dumbbells not only show a different phase behavior from spherical particles, but their phases also differ in mechanical and dynamical properties.…”

Section: Hard and Soft-core Models Of Non-convex Particlesmentioning

confidence: 76%

Packing, entropic patchiness, and self-assembly of non-convex colloidal particles: A simulation perspective

Avendaño

Escobedo

2017

Current Opinion in Colloid & Interface Science

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Recent advances in experimental techniques to synthesise particles with non-convex shapes have provided new challenges and opportunities to the modelling community. The availability of such building blocks has motivated many computational studies on the formation of new materials driven by such complex effects as interpenetration, interlocking, and shape complementarity that, if properly harnessed, have the potential of acting as entropic directional (patchy) interactions in particles with non-convex geometries. This article highlights recent molecular simulation studies of anisotropic non-convex colloidal particles with particular emphasis in particles interacting via excluded volume.

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Degenerate crystals from colloidal dimers under confinement

Cited by 15 publications

References 46 publications

Phase behaviour and gravity-directed self assembly of hard convex spherical caps

Phase behaviour and gravity-directed self assembly of hard convex spherical caps

Nanorings in planar confinement: the role of repulsive surfaces on the formation of lacuna smectics

Packing, entropic patchiness, and self-assembly of non-convex colloidal particles: A simulation perspective

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