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Nesrullajev A. Optical refracting properties, birefringence and order parameter in mixtures of liquid crystals: Direct smectic A – Isotropic and reverse isotropic – Smectic A phase transitions. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2021.117716] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Vitral E, Leo PH, Viñals J. Phase-field model for a weakly compressible soft layered material: morphological transitions on smectic-isotropic interfaces. SOFT MATTER 2021; 17:6140-6159. [PMID: 34080608 DOI: 10.1039/d1sm00488c] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
A coupled phase-field and hydrodynamic model is introduced to describe a two-phase, weakly compressible smectic (layered phase) in contact with an isotropic fluid of different density. A non-conserved smectic order parameter is coupled to a conserved mass density in order to accommodate non-solenoidal flows near the smectic-isotropic boundary arising from density contrast between the two phases. The model aims to describe morphological transitions in smectic thin films under heat treatment, in which arrays of focal conic defects evolve into conical pyramids and concentric rings through curvature dependent evaporation of smectic layers. The model leads to an extended thermodynamic relation at a curved surface that includes its Gaussian curvature, non-classical stresses at the boundary and flows arising from density gradients. The temporal evolution given by the model conserves the overall mass of the liquid crystal while still allowing for the modulated smectic structure to grow or shrink. A numerical solution of the governing equations reveals that pyramidal domains are sculpted at the center of focal conics upon a temperature increase, which display tangential flows at their surface. Other cases investigated include the possible coalescence of two cylindrical stacks of smectic layers, formation of droplets, and the interactions between focal conic domains through flow.
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Affiliation(s)
- Eduardo Vitral
- Department of Mechanical Engineering, University of Nevada, 1664 N. Virginia St., Reno, NV 89557, USA.
| | - Perry H Leo
- Department of Aerospace Engineering and Mechanics, University of Minnesota, 110 Union St. SE, Minneapolis, MN 55455, USA
| | - Jorge Viñals
- School of Physics and Astronomy, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455, USA
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Abstract
We study in this paper the dynamics of molecules leading to the formation of nematic and smectic phases using a mobile 6-state Potts spin model with Monte Carlo simulation. Each Potts state represents a molecular orientation. We show that, with the choice of an appropriate microscopic Hamiltonian describing the interaction between individual molecules modeled by 6-state Potts spins, we obtain the structure of the smectic phase by cooling the molecules from the isotropic phase to low temperatures: molecules are ordered in independent equidistant layers. The isotropic-smectic phase transition is found to have a first-order character. The nematic phase is also obtained with the choice of another microscopic Hamiltonian. The isotropic-nematic phase transition is a second-order one. The real-time dynamics of the molecules leading to the liquid-crystal ordering in each case is shown by a video.
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Al Sallo AS, Walker AJ, Boswell GP. Structure of smectic-A liquid crystals in nonuniform domains: Modeling the impact of imperfect boundaries. Phys Rev E 2020; 101:032703. [PMID: 32289914 DOI: 10.1103/physreve.101.032703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 02/21/2020] [Indexed: 11/07/2022]
Abstract
This paper describes the construction of equilibrium configurations for smectic-A liquid crystals subjected to nonuniform physical boundary conditions, with two-dimensional dependence on the director and layer normal, and a nonlinear layer function. Euler-Lagrange equations are constructed that describe key properties of liquid crystals confined between two boundaries exhibiting spatial imperfections. The results of the model are shown to be consistent with previous published findings in simple domains while results are obtained on how the structure of the liquid crystals changes in response to boundary perturbations. Domain sizes are considered representing those currently used in applications while predictions in smaller domains at the limit of current technologies are also made. In particular, it is shown that the curvature along a boundary impacts on the liquid crystal's structure distant from the boundary feature and therefore previously developed mathematical models, that essentially reduced the problem to a single spatial dimension, cannot be used in such circumstances. Consequences for practical applications are briefly discussed.
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Affiliation(s)
- Ayad S Al Sallo
- School of Computing and Mathematics, University of South Wales, Pontypridd CF37 1DL, United Kingdom
| | - Alan J Walker
- School of Computing, Engineering and Physical Sciences, University of the West of Scotland, Paisley PA1 2BE, United Kingdom
| | - Graeme P Boswell
- School of Computing and Mathematics, University of South Wales, Pontypridd CF37 1DL, United Kingdom
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Vitral E, Leo PH, Viñals J. Role of Gaussian curvature on local equilibrium and dynamics of smectic-isotropic interfaces. Phys Rev E 2019; 100:032805. [PMID: 31639951 DOI: 10.1103/physreve.100.032805] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Indexed: 11/07/2022]
Abstract
Recent research on interfacial instabilities of smectic films has shown unexpected morphologies that are not fully explained by classical local equilibrium thermodynamics. Annealing focal conic domains can lead to conical pyramids, changing the sign of the Gaussian curvature and exposing smectic layers at the interface. In order to explore the role of the Gaussian curvature on the stability and evolution of the film-vapor interface, we introduce a phase-field model of a smectic-isotropic system as a first step in the study. Through asymptotic analysis of the model, we generalize the classical condition of local equilibrium, the Gibbs-Thomson equation, to include contributions from surface bending and torsion and a dependence on the layer orientation at the interface. A full numerical solution of the phase-field model is then used to study the evolution of focal conic structures in smectic domains in contact with the isotropic phase via local evaporation and condensation of smectic layers. As in experiments, numerical solutions show that pyramidal structures emerge near the center of the focal conic owing to evaporation of adjacent smectic planes and to their orientation relative to the interface. Near the center of the focal conic domain, a correct description of the motion of the interface requires the additional curvature terms obtained in the asymptotic analysis, thus clarifying the limitations in modeling motion of hyperbolic surfaces solely driven by mean curvature.
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Affiliation(s)
- Eduardo Vitral
- Department of Aerospace Engineering and Mechanics, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Perry H Leo
- Department of Aerospace Engineering and Mechanics, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Jorge Viñals
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Nesrullajev A. Thermotropic, refracting and birefringent properties in homogeneous mixtures of 4-n-alkyl-4′-cyanobiphenyl mesogens. J Mol Liq 2016. [DOI: 10.1016/j.molliq.2016.01.036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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7
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Texture transformations and thermo-optical properties of nematic mesogen at nematic–isotropic liquid phase transition. J Mol Liq 2014. [DOI: 10.1016/j.molliq.2014.03.029] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Rzoska SJ, Mukherjee PK, Rutkowska M. Does the characteristic value of the discontinuity of the isotropic-mesophase transition in n-cyanobiphenyls exist? JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:375101. [PMID: 22842199 DOI: 10.1088/0953-8984/24/37/375101] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Results of the extended Landau-de Gennes model analysis and experimental studies of the isotropic-nematic (I-N) and isotropic-smectic-A (I-SmA) phase transitions in rod-like liquid crystalline n-alkylcyanobiphenyls are presented. Experiments were carried out as a function of temperature and pressure using the static dielectric permittivity and its 'nonlinear' (strong electric field related) counterpart-the low-frequency nonlinear dielectric effect. Precise estimations of the values of the discontinuity of the isotropic-mesophase transitions (ΔT) for nCB from n = 3-14 have been obtained. It is suggested that for each nCB a unique, characteristic minimal value of ΔT, associated with the I-N-SmA triple point, exists. For 'shorter' nCBs it can be hidden in the negative pressures domain. The possibility of the extension of the 'melting curve' into the negative pressures region as well as the appearance of the 'melting inversion' at high enough pressures is indicated.
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Mukherjee PK. Theoretical model of the frequency and temperature dependence of the complex non-linear dielectric effect in the isotropic phase above the isotropic-smectic-A phase transition. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2012; 35:9705. [PMID: 22526979 DOI: 10.1140/epje/i2012-12028-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 03/19/2012] [Accepted: 04/04/2012] [Indexed: 05/31/2023]
Abstract
Using the Landau model, the temperature and frequency dependence of the complex non-linear dielectric effect in the isotropic phase above the isotropic-smectic-A phase transition is calculated. Comparing the results of the calculations with existing data, we finally conclude that the model provides a description of the isotropic-smectic-A transition that takes all experimentally known features of the non-linear dielectric effect in the isotropic phase into account in a qualitatively correct way.
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Affiliation(s)
- P K Mukherjee
- Department of Physics, Presidency University, Kolkata, India.
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Rzoska SJ, Pawlus S, Czupryński K. Glassy dynamics in the isotropic phase of a smectogenic liquid crystalline compound. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:031710. [PMID: 22060393 DOI: 10.1103/physreve.84.031710] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Revised: 07/29/2011] [Indexed: 05/31/2023]
Abstract
The temperature evolution of the primary relaxation time in the isotropic phase of 4-cyano-4'-tetradecylbiphenyl (14CB) above the isotropic-smectic A (I-SmA) transition is discussed. Based on the enthalpy space and distortion-sensitive analysis, the prevalence of the mode coupling theory (MCT) "critical" and "glassy" dynamics is shown. The obtained singular dependence is related to the MCT critical temperature located approximately 48 K below the clearing (I-SmA) temperature. However, a weak but detectable distortion in the immediate vicinity of the transition occurs. It is also shown that the value of the fragile strength coefficient D(T) is characteristic of a very fragile glassy liquid whereas the steepness index m is typical of a strong one. Both magnitudes anomalously change on approaching the I-SmA phase transition. The static permittivity shows the pretransitional effect linked to the temperature of the hypothetical continuous phase transition located approximately 10.2 K below the I-SmA transition.
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Affiliation(s)
- Sylwester J Rzoska
- Institute of High Pressure Physics, Polish Academy of Sciences, ulica Sokołowska 27/39, PL-00-143 Warsaw, Poland.
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Yilmaz-Canli N, Bilgin-Eran B, Nesrullajev A. Synthesis, mesomorphic and physical properties of two new analogs of Schiff’s base with an alkenic terminal chains. J Mol Struct 2011. [DOI: 10.1016/j.molstruc.2010.12.056] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Sigdel KP, Iannacchione GS. Study of the isotropic to smectic-A phase transition in liquid crystal and acetone binary mixtures. J Chem Phys 2010; 133:174501. [PMID: 21054045 DOI: 10.1063/1.3502112] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The first-order transition from the isotropic (I) to smectic-A (Sm A) phase in the liquid crystal 4-cyano-4(')-decylbiphenyl (10CB) doped with the polar solvent acetone (ace) has been studied as a function of solvent concentration by high-resolution ac-calorimetry. Heating and cooling scans were performed for miscible 10CB+ace samples having acetone mole fractions from x(ace)=0.05 (1 wt %) to 0.36 (10%) over a wide temperature range from 310 to 327 K. Two distinct first-order phase transition features are observed in the mixture whereas there is only one transition (I-Sm A) in the pure 10CB for that particular temperature range. Both calorimetric features reproduce on repeated heating and cooling scans and evolve with increasing x(ace) with the high-temperature feature relatively stable in temperature but reduced in size while the low-temperature feature shifts dramatically to lower temperature and exhibits increased dispersion. The coexistence region increases for the low-temperature feature but remains fairly constant for the high-temperature feature as a function of x(ace). Polarizing optical microscopy supports the identification of a smectic phase below the high-temperature heat capacity signature indicating that the low-temperature feature represents an injected smectic-smectic phase transition. These effects may be the consequence of screening the intermolecular potential of the liquid crystals by the solvent that stabilizes a weak smectic phase intermediate of the isotropic and pure smectic-A.
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Affiliation(s)
- Krishna P Sigdel
- Department of Physics, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA
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Soulé ER, Abukhdeir NM, Rey AD. Thermodynamics, Transition Dynamics, and Texturing in Polymer-Dispersed Liquid Crystals with Mesogens Exhibiting a Direct Isotropic/Smectic-A Transition. Macromolecules 2009. [DOI: 10.1021/ma901569y] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ezequiel R. Soulé
- Institute of Materials Science and Technology (INTEMA), University of Mar del Plata and National Research Council (CONICET), J.B. Justo 4302, 7600 Mar del Plata, Argentina
| | | | - Alejandro D. Rey
- Department of Chemical Engineering, McGill University, Montréal, Québec H3A 2B2, Canada
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Abukhdeir NM, Rey AD. Nonisothermal model for the direct isotropic/smectic-A liquid-crystalline transition. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:11923-11929. [PMID: 19788233 DOI: 10.1021/la9015965] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
An extension to a high-order model for the direct isotropic/smectic-A liquid-crystalline phase transition was derived to take into account thermal effects including anisotropic thermal diffusion and latent heat of phase ordering. Multiscale multitransport simulations of the nonisothermal model were compared to isothermal simulation, showing that the presented model extension corrects the standard Landau-de Gennes prediction from constant growth to diffusion-limited growth under shallow quench/undercooling conditions. Nonisothermal simulations, where metastable nematic preordering precedes smectic-A growth, were also conducted, and novel nonmonotonic phase-transformation kinetics were observed.
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Abukhdeir NM, Rey AD. Metastable Nematic Preordering in Smectic Liquid Crystalline Phase Transitions. Macromolecules 2009. [DOI: 10.1021/ma900796b] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Alejandro D. Rey
- Department of Chemical Engineering, McGill University, Montréal, Québec H3A 2B2, Canada
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Biscari P, Calderer MC, Terentjev EM. Landau-de Gennes theory of isotropic-nematic-smectic liquid crystal transitions. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 75:051707. [PMID: 17677084 DOI: 10.1103/physreve.75.051707] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2006] [Revised: 02/14/2007] [Indexed: 05/16/2023]
Abstract
We propose a Landau-de Gennes variational theory fit to simultaneously describe isotropic, nematic, smectic- A , and smectic- C phases of a liquid crystal. The unified description allows us to deal with systems in which one, or all, of the order parameters develop because of the influence of defects, external fields and/or boundary conditions. We derive the complete phase diagram of the system, that is, we characterize how the homogeneous minimizers depend on the value of the constitutive parameters. The coupling between the nematic order tensor and the complex smectic order parameter generates an elastic potential which is a nonconvex function of the gradient of the smectic order parameter. This lack of convexity yields in turn a loss of regularity of the free-energy minimizers. We then consider the effect on an infinitesimal second-order regularization term in the free-energy functional, which fixes the optimal number of defects in the singular configurations.
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Affiliation(s)
- Paolo Biscari
- Dipartimento di Matematica, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, Italy.
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Srivastava A, Sa D, Singh S. Influence of pressure on the electric-field-induced phase transitions in liquid crystals. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2006; 20:63-9. [PMID: 16733640 DOI: 10.1140/epje/i2005-10121-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2005] [Accepted: 03/27/2006] [Indexed: 05/09/2023]
Abstract
Within the framework of Landau-de-Gennes formulation, we analyse the effect of pressure on electric-field-induced phase transitions in a liquid crystal which shows spontaneously an isotropic-smectic A transition. Inferring from the experimental pressure dependences on the layer spacing in smectic A phase, as well as the nematic-smectic A metastable temperature T*(AN), we incorporated the pressure dependence in the free energy through (the surface energy term) and the coupling between the quadrupolar nematic ordering Q(ij) and the smectic order parameter psi. From the S-T phase diagram, we found that the stability of field-induced nematic phase increases with pressure, whereas the discontinuity of the transition decreases. Also, the region where paranematic phase transits directly to smectic A phase increases with pressure.
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Affiliation(s)
- A Srivastava
- Department of Physics, Banaras Hindu University, Varanasi-221005, India
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Mukherjee PK. Anomalous heat capacity above the isotropic-chiral-smectic-C phase transition. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 71:061704. [PMID: 16089749 DOI: 10.1103/physreve.71.061704] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2004] [Revised: 04/04/2005] [Indexed: 05/03/2023]
Abstract
A phenomenological model is developed to describe the isotropic-chiral-smectic-C phase transition. The anomalous part of the heat capacity of the chiral-smectic-C liquid crystals above the isotropic-chiral-smectic-C phase transition is calculated using Landau's fluctuation theory. The temperature dependence of the heat capacity above the transition point is calculated first for the Gaussian model and then taking the cubic and the quartic terms as a perturbation. The theoretical results are found to be in good agreement with experiment.
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Affiliation(s)
- Prabir K Mukherjee
- Department of Physics, Haldia Govt. College, P.O.-Debhog, Dist.-East Midnapore, 721657, India.
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Ambrozic M, Kralj S, Sluckin TJ, Zumer S, Svensek D. Annihilation of edge dislocations in smectic-A liquid crystals. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2004; 70:051704. [PMID: 15600637 DOI: 10.1103/physreve.70.051704] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2003] [Revised: 07/30/2004] [Indexed: 05/24/2023]
Abstract
This paper presents a theoretical study of the annihilation of edge dislocations in the same smectic plane in a bulk smectic-A phase. We use a time-dependent Landau-Ginzburg approach where the smectic ordering is described by the complex order parameter psi( r--> ,t) =eta e(iphi) . This quantity allows both the degree of layering and the position of the layers to be monitored. We are able to follow both precollision and postcollision regimes, and distinguish different early and late behaviors within these regimes. The early precollision regime is driven by changes in the phi ( r--> ) configuration. The relative velocity of the defects is approximately inversely proportional to the interdefect separation distance. In the late precollision regime the symmetry changes within the cores of defects also become influential. Following the defect collision, in the early postcollision stage, bulk layer order is approached exponentially in time. At very late times, however, there seems to be a long-time power-law tail in the order parameter fluctuation relaxation.
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Affiliation(s)
- M Ambrozic
- Engineering Ceramics Department, Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
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Molecular dynamics above the smectic A-isotropic phase transition of thermotropic liquid crystals studied by NMR. Chem Phys Lett 2004. [DOI: 10.1016/j.cplett.2004.05.055] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Mukherjee PK, Pleiner H, Brand HR. Landau model of the smectic C–isotropic phase transition. J Chem Phys 2002. [DOI: 10.1063/1.1509055] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Mukherjee PK, Rzoska SJ. Pressure effect on the smectic-A-isotropic phase transition. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2002; 65:051705. [PMID: 12059575 DOI: 10.1103/physreve.65.051705] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2001] [Revised: 11/07/2001] [Indexed: 05/23/2023]
Abstract
We examine the effect of pressure on the smectic-A-isotropic phase transition within the Landau phenomenological theory. The influence of pressure on the smectic-A-isotropic phase transition is discussed by varying the coupling between the orientational and the translational order parameter. The transition is found to be of first order even at elevated pressure. The pressure dependence nonlinear dielectric effect in the isotropic phase of the smectic-A-isotropic transition is calculated. The theoretical results are in good qualitative agreement with available experimental results.
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Affiliation(s)
- Prabir K Mukherjee
- Haldia Government College, P.O. Debhog, District Midnapore, West Bengal 721657, India and Theoretische Physik III, Universität Bayreuth, D-95440 Bayreuth, Germany
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Luckhurst GR, Saielli G, Sluckin TJ. Shear-induced structural changes of a smectic-A phase: a computer simulation study. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2002; 65:041717. [PMID: 12005856 DOI: 10.1103/physreve.65.041717] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2001] [Indexed: 05/23/2023]
Abstract
We have carried out a Monte Carlo simulation of a thin sample of the smectic-A phase of the Gay-Berne mesogen GB(4.4,20.0,1,1) sandwiched between two plates and subject to shear. The smectic layers are perpendicular to the confining plates and are pinned at the boundaries. The thickness of the samples studied ranges from about three to twenty molecules. The layers tilt progressively with increasing shear, but rearrange themselves at a critical shear. At this critical shear the layers melt near the center of the sample and reform with a reduced tilt consistent with the layer pinning at the walls. The pseudodynamics of this process as the smectic layers melt and are reformed have been followed during the simulation. The critical layer tilt at which slippage takes place tends to a constant value for thick samples, but for very thin samples the critical shear tends toward half a smectic layer, with a significantly reduced translational order near the sample center just before the critical shear. The simulation results are consistent with the predictions of the mean field theory of this phenomenon developed by Mottram et al.
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Affiliation(s)
- G R Luckhurst
- Department of Chemistry and Southampton Liquid Crystal Institute, University of Southampton, Southampton SO17 1BJ, United Kingdom
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