Order-disorder molecular model of the smectic- A–smectic-C phase transition in materials with conventional and anomalously weak layer contraction

M.V. Gorkunov, Mikhail Osipov, J.P.F. Lagerwall, F. Glesselmann

Research output: Contribution to journalArticle

54 Citations (Scopus)

Abstract

We develop a molecular-statistical theory of the smectic-A–smectic-C transition which is described as a transition of the order-disorder type. The theory is based on a general expansion of the effective interaction potential and employs a complete set of orientational order parameters. All the order parameters of the smectic-C phase including the tilt angle are calculated numerically as functions of temperature for a number of systems which correspond to different transition scenario. The effective interaction potential and the parameters of the transition are also calculated for specific molecular models based on electrostatic and induction interaction between molecular dipoles. The theory successfully reproduces the main properties of both conventional and so-called “de Vries–type” smectic liquid crystals, clarifies the origin of the anomalously weak layer contraction and describes the tricritical behavior at the smectic-A–smectic-C transition. The “de Vries behavior,” i.e., anomalously weak layer contraction is also obtained for a particular molecular model based on interaction between longitudinal molecular dipoles. A simple phenomenological model is presented enabling one to obtain explicit expressions for the layer spacing and the tilt angle which are used to fit the experimental data for a number of materials.

LanguageEnglish
Number of pages16
JournalPhysical Review E
Volume76
Issue number5
DOIs
Publication statusPublished - 19 Nov 2007

Fingerprint

contraction
Disorder
Contraction
Phase Transition
disorders
Tilt
Interaction
Order Parameter
Dipole
interactions
Model-based
dipoles
Angle
Model
Liquid Crystal
Electrostatics
Spacing
Proof by induction
induction
liquid crystals

Keywords

  • phase transition
  • liquid crystals
  • orientational order parameters
  • molecular dipoles

Cite this

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title = "Order-disorder molecular model of the smectic- A–smectic-C phase transition in materials with conventional and anomalously weak layer contraction",
abstract = "We develop a molecular-statistical theory of the smectic-A–smectic-C transition which is described as a transition of the order-disorder type. The theory is based on a general expansion of the effective interaction potential and employs a complete set of orientational order parameters. All the order parameters of the smectic-C phase including the tilt angle are calculated numerically as functions of temperature for a number of systems which correspond to different transition scenario. The effective interaction potential and the parameters of the transition are also calculated for specific molecular models based on electrostatic and induction interaction between molecular dipoles. The theory successfully reproduces the main properties of both conventional and so-called “de Vries–type” smectic liquid crystals, clarifies the origin of the anomalously weak layer contraction and describes the tricritical behavior at the smectic-A–smectic-C transition. The “de Vries behavior,” i.e., anomalously weak layer contraction is also obtained for a particular molecular model based on interaction between longitudinal molecular dipoles. A simple phenomenological model is presented enabling one to obtain explicit expressions for the layer spacing and the tilt angle which are used to fit the experimental data for a number of materials.",
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Order-disorder molecular model of the smectic- A–smectic-C phase transition in materials with conventional and anomalously weak layer contraction. / Gorkunov, M.V.; Osipov, Mikhail; Lagerwall, J.P.F.; Glesselmann, F.

In: Physical Review E, Vol. 76, No. 5, 19.11.2007.

Research output: Contribution to journalArticle

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