Simulation of Surface-Enhanced Ordering in Smectic Films

Abukhdeir, Nasser Mohieddin; Rey, Alejandro D.

doi:10.4028/www.scientific.net/ssp.139.135

Cited by 7 publications

(10 citation statements)

References 29 publications

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“…This platform does not support adaptive mesh refinement, thus a uniform mesh was used with a density of approximately 14.8 nodes/nm 2 . Previous simulations using this model and numerical method have shown good agreement with both past experimental and theoretical findings (10,11). Additionally, exhaustive past work using this numerical method and the Landau-de Gennes model for the first-order isotropic/nematic phase transition (26-29) has served to further validate this simulation approach.…”

Section: Simulation Methods and Conditionssupporting

confidence: 70%

“…In this effort a comprehensive approach has been developed for the determination of phenomenological parameters for the model and efficient phase diagram computation (9). Following this, numerical simulation was used to study phase transition kinetics and defect dynamics (10), surface effects (11), and most recently spherulite growth (12). In addition to these simulation studies, theoretical contributions have been made to the study of smectic-A filamentary growth and buckling (13,14).…”

Section: Introductionmentioning

confidence: 99%

“…The current work studies an alternate initial configuration where the nucleus is homogeneously, or "ideally," oriented. This and past work (10)(11)(12)14) focuses on rod-like low molecular mass liquid crystals and phenomenological parameters are based, in part, on experimental data from 12CB (dodecyl-cyanobiphenyl). This work neglects nucleation mechanisms, thermal fluctuations, heat of transition, impurities, and convective flow while taking into account energetically the intercoupling between orientational/translational order and variation of smectic layer spacing.…”

Section: Introductionmentioning

confidence: 99%

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Shape-dynamic growth, structure, and elasticity of homogeneously oriented spherulites in an isotropic/smectic-A mesophase transition

Abukhdeir

Rey

2009

Liquid Crystals

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A Landau-de Gennes model that integrates the nematic quadrupolar tensor order parameter and complex smectic-A order parameters is used to simulate the two-dimensional growth of an initially homogeneous smectic-A spherulite in an isotropic matrix. These simulations are performed in the shape-dynamic (nano-scale) regime of growth under two material conditions: isotropic nematic elasticity and equal splay-bend nematic elasticity. A comparison of the growth kinetics, spherulite morphology, interfacial/bulk energy landscapes between both cases is made showing that equal nematic splay-bend elasticity is required to reproduce past experimental and theoretical observations. Additionally, a previously unknown undulation instability during spherulite growth is found which, in conjunction with preferred planar anchoring and defect shedding mechanisms at micron length scales, could explain the formation mechanism of focal conic curvature defects and ultimately smectic-A "batonnet" structures observed experimentally. of this mesophase via modelling and simulation. The key role that this mesophase plays in biological systems alone shows the importance of this single contribution of de Gennes. In his Nobel lecture in 1991, he states that "smectics bring me naturally to another important feature of complex fluids -namely that, in our days, it is sometimes possible to create new forms of matter" which alludes to the types of applications of smectics that could be developed in the future and to their roles in biological systems.The most simple of the smectics is the smectic-A mesophase, which displays lamellar translational ordering, in addition to the orientational ordering of nematics. Recently an increasing amount of interest in this mesophase, in particular of materials exhibiting a direct isotropic/smectic-A (disordered/ordered) transition, has resulted in many experimental and theoretical results. Nonetheless, the understanding of this mesophase is in a nascent stage. Much of this is due to the time and length scales at which the structures and dynamics occur being on the nanoscale. These properties provide a obvious application of theoretical study through modelling and simulation in order to both enhance experimental research and make predictions independently.A fascinating range of liquid crystal growth morphologies have been the focus on much study (6). The smectic-A mesophase, with its lamellar ordering on the molecular scale, exhibits growth, defect, and texture phenomena not seen in the nematic phases, including the lamellar-like cholesteric mesophase. Focusing on the growth phenomena solely, on transition from the isotropic/disordered phase, a variety of self-assembled smectic-A structures have been observed to form. These unique morphologies can be attributed to complex dynamics involving interfacial tension anisotropy, which results in preferred anchoring, and bulk texturing.The current study is a part of an overall effort to understand kinetics, dynamics, and morphology of the direct isotropic/smectic-A liquid cry...

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Section: Simulation Methods and Conditionssupporting

confidence: 70%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Shape-dynamic growth, structure, and elasticity of homogeneously oriented spherulites in an isotropic/smectic-A mesophase transition

Abukhdeir

Rey

2009

Liquid Crystals

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“…It further led to prediction of twist-grain-boundary phases, liquidcrystal analogues of the Abrikosov flux lattice in type-II superconductors [9]. Most recently, it has led to calculations for smectic layer configurations in confined geometries [10][11][12][13][14][15][16], which may be useful for design of smectic devices [17].…”

Section: Introductionmentioning

confidence: 99%

Modeling smectic layers in confined geometries: Order parameter and defects

2014

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We identify problems with the standard complex order parameter formalism for smectic-A (SmA) liquid crystals and discuss possible alternative descriptions of smectic order. In particular, we suggest an approach based on the real smectic density variation rather than a complex order parameter. This approach gives reasonable numerical results for the smectic layer configuration and director field in sample geometries and can be used to model smectic liquid crystals under nanoscale confinement for technological applications.

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“…Cutting-edge experimental work on enhancement of the photolithographic process using block copolymer films [6,7,9] could benefit from the presented modelling and simulation approach in addition to the generation of material specific model parameters [13], incorporation of edge-effects [39], and bulk-field terms.…”

Section: Discussionmentioning

confidence: 99%

Development of a Novel Low Temperature Co-Fired Ceramics System Composed of Two Different Co-Firable Low Temperature Co-Fired Ceramics Materials

Murata

Ohga

Sugimoto

2006

jjap

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Two-dimensional simulations of the coarsening process of the isotropic/smectic-A phase transition are presented using a high-order Landau-de Gennes-type free energy model. Defect annihilation laws for smectic disclinations, elementary dislocations and total dislocation content are determined. The computed evolution of the orientational correlation length and disclination density is found to be in agreement with previous experimental observations showing that disclination interactions dominate the coarsening process. The mechanism of smectic disclination movement, limited by the absorption and emission of elementary dislocations, is found to be facilitated by curvature walls connecting interacting disclinations. At intermediate times in the coarsening process, split-core dislocation formation and interactions displaying an effective disclination quadrupole configuration are observed. This work provides the framework for further understanding of the formation and dynamics of the diverse set of curvature defects observed in smectic liquid crystals and other layered material systems.

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Simulation of Surface-Enhanced Ordering in Smectic Films

Cited by 7 publications

References 29 publications

Shape-dynamic growth, structure, and elasticity of homogeneously oriented spherulites in an isotropic/smectic-A mesophase transition

Shape-dynamic growth, structure, and elasticity of homogeneously oriented spherulites in an isotropic/smectic-A mesophase transition

Modeling smectic layers in confined geometries: Order parameter and defects

Development of a Novel Low Temperature Co-Fired Ceramics System Composed of Two Different Co-Firable Low Temperature Co-Fired Ceramics Materials

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