Biaxial Nematic Phase in Model Bent-Core Systems

Grzybowski, Piotr; Longa, Lech

doi:10.1103/physrevlett.107.027802

Cited by 28 publications

(30 citation statements)

References 33 publications

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“…In the latter work, which assumes the same second-rank quadrupolar interaction, the dipolar interaction is more comprehensive and also depends on the relative position of the two interacting molecules. No polar phases were found in either study, in agreement with a density functional theory developed by Grzybowski and Longa, [26] a series of atomistic simulations by Peláez and Wilson [27] and a two-particle cluster theory by Osipov and Pajak. [28] However, by contrast, Ghoshal et al [25] suggested that the unrealistic Heisenberg form of dipolar interaction potential used by Bates [24] might form polar phases.…”

Section: Introductionsupporting

confidence: 79%

“…We discuss the applicability of such a model later, but note here that other authors have used more realistic models for the dipolar interaction both in density functional theory, [26] lattice Monte Carlo simulations [25] and two-site cluster theory. [28] These studies include the effect of short-range order which, of necessity, do not appear in our molecular field theory.…”

Section: Discussionmentioning

confidence: 98%

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Molecular field theory for polar, biaxial bent-core nematics

Sluckin

Luckhurst

2016

Liquid Crystals

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We have studied a polar, biaxial nematic liquid crystal formed from bent-core molecules using molecular field theory. The model includes a simple Heisenberg-form dipolar intermolecular interaction in addition to the usual quadrupolar nematic interaction, and mimics a system consisting of nematogenic bent-core molecules with an large transverse dipole along the bisector of the two molecular arms. Such systems are regarded as good candidates for biaxial nematic liquid crystals. In principle, the molecular dipoles can align, thus stabilizing the ordering of the minor axes. Our calculations predict that, for suitable values of the bent-core interarm angle, the biaxial nematic phase can be stabilized at higher temperatures than in the absence of the transverse dipole. In general, the transverse macroscopic polar order stabilizes the biaxial nematic phase. In particular, for a large enough dipolar interaction, the Landau point in the pure biaxial nematic develops into a line of first-order polar biaxial nematic-to-isotropic phase transitions.

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Section: Introductionsupporting

confidence: 79%

Section: Discussionmentioning

confidence: 98%

Molecular field theory for polar, biaxial bent-core nematics

Sluckin

Luckhurst

2016

Liquid Crystals

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“…33 A plethora of models have thus been devised to understand the three-dimensional bulk behavior of these systems. [40][41][42][43][44] Yet relatively little theoretical attention has been paid to related models in two dimensions. [45][46][47] Here, we consider the two-dimensional phase behavior of a bent-needle model in both its chiral zig-zag and achiral bow-shaped configurations (Fig.…”

Section: Introductionmentioning

confidence: 99%

Phase ordering of zig-zag and bow-shaped hard needles in two dimensions

Tavarone

Stark

2015

The Journal of Chemical Physics

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We perform extensive Monte Carlo simulations of a two-dimensional bent hard-needle model in both its chiral zig-zag and its achiral bow-shape configurations and present their phase diagrams. We find evidence for a variety of stable phases: isotropic, quasi-nematic, smectic-C, anti-ferromorphic smectic-A, and modulated-nematic. This last phase consists of layers formed by supramolecular arches. They create a modulation of the molecular polarity whose period is sensitively controlled by molecular geometry. We identify transition densities using correlation functions together with appropriately defined order parameters and compare them with predictions from Onsager theory. The contribution of the molecular excluded area to deviations from Onsager theory and simple liquid crystal phase morphology is discussed. We demonstrate the isotropic-quasi-nematic transition to be consistent with a Kosterlitz-Thouless disclination unbinding scenario. C 2015 AIP Publishing LLC. [http://dx

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“…The theoretical exploration of stable biaxial nematic order has been based on biaxial hard-body and Gay-Berne-type soft potential models, using specific particle shapes such as spheroplatelets [4,5], biaxial ellipsoids [6,7] and bent-core particles [8][9][10][11]. The biaxial nematic phase has also been found in binary mixtures of uniaxial plate-like and rod-like particles [12][13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Effect of shape biaxiality on the phase behavior of colloidal liquid-crystal monolayers

Gonzalez-Pinto

Martı́nez-Ratón

Velasco

et al. 2015

Phys. Chem. Chem. Phys.

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We extend our previous work on monolayers of uniaxial particles [J. Chem. Phys. 140, 204906 (2014)] to study the effect of particle biaxiality on the phase behavior of liquid-crystal monolayers.Particles are modelled as board-like hard bodies with three different edge lengths σ 1 ≥ σ 2 ≥ σ 3 , and use is made of the restricted-orientation approximation (Zwanzig model). A density-functional formalism based on the fundamental-measure theory is used to calculate phase diagrams for a wide range of values of the largest aspect ratio (κ 1 = σ 1 /σ 3 ∈ [1, 100]). We find that particle biaxiality in general destabilizes the biaxial nematic phase already present in monolayers of uniaxial particles.While plate-like particles exhibit strong biaxial ordering, rod-like ones with κ 1 > 21.34 exhibit reentrant uniaxial and biaxial phases. As particle geometry is changed from uniaxial-to increasingly biaxial-rod-like, the region of biaxiality is reduced, eventually ending in a critical-end point. For κ 1 > 60, a density gap opens up in which the biaxial nematic phase is stable for any particle biaxiality. Regions of the phase diagram where packing-fraction inversion occurs (i.e. packing fraction is a decreasing function of density) are found. Our results are compared with the recent experimental studies on nematic phases of magnetic nanorods.

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Biaxial Nematic Phase in Model Bent-Core Systems

Cited by 28 publications

References 33 publications

Molecular field theory for polar, biaxial bent-core nematics

Molecular field theory for polar, biaxial bent-core nematics

Phase ordering of zig-zag and bow-shaped hard needles in two dimensions

Effect of shape biaxiality on the phase behavior of colloidal liquid-crystal monolayers

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