The structure and energetics of defects in liquid crystals

Chandrasekhar, S.; Ranganath, G. S.

doi:10.1080/00018738600101941

Cited by 227 publications

(155 citation statements)

References 63 publications

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“…These defects are points or lines along which it is impossible to define an order parameter in a system in which order is otherwise present. In this paper we shall be concerned with point defects, sometimes known as hedgehogs [2]. We shall concentrate on model magnetic and nematic liquid crystals, but we note that this type of defect can occur in a variety of ordered media [3].…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo Simulation of the Hedgehog Defect Core in Spin Systems

et al. 1995

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Abstract.-The core structures of hedgehog point disclinations in Heisenberg magnets and Lebwohl-Lasher nematic liquid crystals have been investigated by Monte Carlo simulation. We find qualitative agreement with the theoretical predictions of Schopohl and Sluckin that the magnetic defects have smaller cores. We also find some evidence for the picture of Penzenstadler and Trebin in which spherical symmetry of the nematic hedgehog core is broken, and the core region can be considered as a disclination line of index l/2. Finally we make some general comments about the significance of our results in the context of other recent theoretical speculations.

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Section: Introductionmentioning

confidence: 99%

Monte Carlo Simulation of the Hedgehog Defect Core in Spin Systems

et al. 1995

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“…At other regions, the polarization changes through the sample, resulting in a bright region. This implies that for a defect of strength s, one will observe 4s dark brushes [23]. If the cross-polarizer setup is rotated then brushes will rotate in the same (opposite) direction for positive (negative) windings.…”

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confidence: 99%

Measuring cosmic defect correlations in liquid crystals

Srivastava

Ray

2004

Phys. Rev. D

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From the theory of topological defect formation proposed for the early universe, the so called Kibble mechanism, it follows that the density correlation functions of defects and anti-defects in a given system should be completely determined in terms of a single length scale ξ, the relevant domain size, which is proportional to the average inter-defect separation r av . Thus, when lengths are expressed in units of r av , these distributions should show universal behavior, depending only on the symmetry of the order parameter, and space dimensions. We have verified this prediction by analyzing the distributions of defects/anti-defects formed during the isotropic-nematic phase transition in a thin layer in a liquid crystal sample. Our experimental results confirm this prediction and are in reasonable agreement with the results of numerical simulations.

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“…[19][20][21] Our core radius, which we denote by x c , is also of the same order as values observed for liquid crystalline melts. 22 Since our uniaxial energy density investigations resulted in disclinations with similar characteristics, 1-3 these results are not unexpected. What is important to emphasize is that, since both Q 1 and Q 2 are nonvanishing for xϾx c , the states obtained here are biaxial.…”

Section: A Radial Expansion "ì1…mentioning

confidence: 53%

Biaxial disclinated states in nematic elastomers

Fried

Korchagin

Todres

2003

The Journal of Chemical Physics

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We use a continuum model to investigate the isochoric axial contraction and expansion of a right circular cylindrical specimen composed of a nematic elastomer that is cross-linked in a uniaxial state and then annealed. We build on previous work by relaxing the constraint that the molecular conformation be spherical or uniaxial, allowing instead for biaxiality. The material exhibits an energetic preference for states involving a disclination of strength ϩ1 along the cylinder axis surrounded by a region in which the conformation of the polymer chains is indeed biaxial. We show that such states represent minimizers of the total free-energy. Also, the reactive pressure necessary to enforce the constraint of material incompressibility within the disclination core is found to be reduced by an order of magnitude when the conformation is biaxial rather than uniaxial. A bifurcation analysis is used to analytically determine the thresholds of axial expansion and contraction at which the material prefers a disclinated state. These thresholds are found to be consistent with numerical predictions. Finally, the stability of the solutions for the studied parameters is also investigated.

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The structure and energetics of defects in liquid crystals

Cited by 227 publications

References 63 publications

Monte Carlo Simulation of the Hedgehog Defect Core in Spin Systems

Monte Carlo Simulation of the Hedgehog Defect Core in Spin Systems

Measuring cosmic defect correlations in liquid crystals

Biaxial disclinated states in nematic elastomers

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