Molecular Graphics of Convex Body Fluids

Gabriel, Adrian T.; Meyer, Timm; Germano, Guido

doi:10.1021/ct700192z

Cited by 60 publications

(46 citation statements)

References 38 publications

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“…the w vectors on a given plane perpendicular to n preferentially point to the same direction. Additional insights on the onset of the N * S phase are provided by the correlation functions g (R ) and g A glance at two snapshots [43] also reported in Fig. 7 gives a visual support of this interpretation.…”

Section: A Phase Diagrams From Mc-nptsupporting

confidence: 59%

“…8, bottom left) does not provide indication of translational order within each single layer, and ψ 6 is found to be very small. This screw-smectic phase, globally uniaxial with the main director perpendicular to the layers, is • ] because of the limitations in the QMGA software [43]. For this reason, this color coding will not be further exploited in the remaining of the paper.…”

Section: A Phase Diagrams From Mc-nptmentioning

confidence: 99%

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Self-assembly of hard helices: a rich and unconventional polymorphism

et al. 2014

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Hard helices can be regarded as a paradigmatic elementary model for a number of natural and synthetic soft matter systems, all featuring the helix as their basic structural unit: from natural polynucleotides and polypeptides to synthetic helical polymers; from bacterial flagella to colloidal helices. Here we present an extensive investigation of the phase diagram of hard helices using a variety of methods. Isobaric Monte Carlo numerical simulations are used to trace the phase diagram: on going from the low-density isotropic to the high-density compact phases, a rich polymorphism is observed exhibiting a special chiral screw-like nematic phase and a number of chiral and/or polar smectic phases. We present a full characterization of the latter, showing that they have unconventional features, ascribable to the helical shape of the constituent particles. Equal area construction is used to locate the isotropic-to-nematic phase transition, and results are compared with those stemming from an Onsager-like theory. Density functional theory is also used to study the nematic-to-screw-nematic phase transition: within the simplifying assumption of perfectly parallel helices, we compare different levels of approximation, that is second-and third-virial expansions and Parsons-Lee correction.arXiv:1408.1199v1 [cond-mat.soft] 6 Aug 2014 2

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Section: A Phase Diagrams From Mc-nptsupporting

confidence: 59%

Section: A Phase Diagrams From Mc-nptmentioning

confidence: 99%

Self-assembly of hard helices: a rich and unconventional polymorphism

et al. 2014

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“…Image was created with the program QMGA. 69 is also exhibited by the fcc-like crystal but only for κ 0.873. For smaller value of κ, its value of φ increases and gets closer and closer to that for the bco-like crystal.…”

Section: Dense Packing Constructionsmentioning

confidence: 97%

“…Images were created using the program QMGA. 69 versus φ [ Fig. 7(b)] curves, provided that p is sufficiently low so that the complete transformation of a elo-like configuration into a bco-like crystal is facilitated.…”

Section: A Equilibrium Phase Behaviormentioning

confidence: 99%

Hard convex lens-shaped particles: Densest-known packings and phase behavior

Cinacchi

Torquato

2015

The Journal of Chemical Physics

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By using theoretical methods and Monte Carlo simulations, this work investigates dense ordered packings and equilibrium phase behavior (from the low-density isotropic fluid regime to the highdensity crystalline solid regime) of monodisperse systems of hard convex lens-shaped particles as defined by the volume common to two intersecting congruent spheres. We show that, while the overall similarity of their shape to that of hard oblate ellipsoids is reflected in a qualitatively similar phase diagram, differences are more pronounced in the high-density crystal phase up to the densest-known packings determined here. In contrast to those non-(Bravais)-lattice two-particle basis crystals that are the densest-known packings of hard (oblate) ellipsoids, hard convex lens-shaped particles pack more densely in two types of degenerate crystalline structures: (i) non-(Bravais)-lattice two-particle basis body-centered-orthorhombic-like crystals and (ii) (Bravais) lattice monoclinic crystals. By stacking at will, regularly or irregularly, laminae of these two crystals, infinitely degenerate, generally non-periodic in the stacking direction, dense packings can be constructed that are consistent with recent organizing principles. While deferring the assessment of which of these dense ordered structures is thermodynamically stable in the high-density crystalline solid regime, the degeneracy of their densest-known packings strongly suggests that colloidal convex lens-shaped particles could be better glass formers than colloidal spheres because of the additional rotational degrees of freedom. C 2015 AIP Publishing LLC. [http://dx

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“…Their equation of state was calculated and the phases formed identified mostly by direct visualization using the program QMGA. 45 Full quantitative analysis of their features along the lines presented in the previous work 11 is deferred to a subsequent paper. Specifically, the values of R* investigated were: 1/ √ 2π , 0.45, 0.55, 0.7, 1, 1.5, 1.6, 2, 5, 10, 100.…”

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confidence: 99%

Phase behavior of hard spherical caps

Cinacchi

2013

The Journal of Chemical Physics

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This work reports on the phase behavior of hard spherical caps in the interval of particle shapes delimited by the hard platelet and hemispherical cap models. These very simple model colloidal particles display a remarkably complex phase behavior featuring a competition between isotropicnematic phase separation and clustering as well as a sequence of structures, from roundish to lacy aggregates to no ordinary hexagonal columnar mesophases, all characterized by groups of particles tending to arrange on the same spherical surface. This behavior parallels that one of many molecular systems forming micelles but here it is purely entropy-driven. © 2013 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4822038]The self-assembly of molecular and colloidal systems has always, and nowadays especially, attracted much attention. 1 Recently, in the case of colloids, there has been significant progress in the synthesis of particles of different shape and size as well as in the techniques to visualize the structures they form. 2 These experimental advances offer concrete chances to observe those phase behaviors predicted by theory and numerical simulation; new results from these can in turn stimulate further experimental research. 3 One current example is provided by hard polyhedral particles, to which much numerical and experimental effort is being dedicated. [4][5][6] In theory and simulation, colloidal particles are indeed often assumed to interact through hard-body interactions as these are predominant in directing their packing and shown over the years to be sufficient for the stabilization of a variety of entropy-driven complex fluid phases: nematic (N), 7 smectic, 8 columnar (C), 9 and even cubic gyroid 10 phases can all be obtained in systems of hard-body particles of suitable shape and size.This work considers a special class of hard-body model colloidal particles and examines by numerical simulation their phase behavior featuring both phase separation and aggregation phenomena.The particles are hard spherical caps (HSCs); a preliminary account of their intriguing phase behavior has been given in Ref. 11. Each of these particles is the portion of the surface of a sphere of radius R subtended by an angle θ . The area of this portion is set equal to σ 2 , with σ the unit of length; any particle of this type is thus identified by R* = R/σ (or θ ). By varying R*, hard, generally concave and infinitely thin, particles can be obtained going from the hard platelet, (R* → ∞), through the hard hemispherical cap (R * = 1/ √ 2π ), to the hard sphere (R * = 1/2 √ π) models. It is actually those lens-, bowl-, and vase-like particles that lay in between these limits that are most interesting.HSCs fit current interest for a variety of reasons. These are primarily fundamental but also related to the issues of a) Electronic mail: giorgio.cinacchi@uam.es practical relevance, given, e.g., the wide range of possibilities that nano-sized hollowed particles may offer in catalysis and drug delivery. 12 Several are the viewpoints HSCs can be ...

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Molecular Graphics of Convex Body Fluids

Cited by 60 publications

References 38 publications

Self-assembly of hard helices: a rich and unconventional polymorphism

Self-assembly of hard helices: a rich and unconventional polymorphism

Hard convex lens-shaped particles: Densest-known packings and phase behavior

Phase behavior of hard spherical caps

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