Nematic liquid crystals: from Maier-Saupe to a continuum theory

John M. Ball, Apala Majumdar

Research output: Contribution to journalArticle

82 Citations (Scopus)

Abstract

We define a continuum energy functional that effectively interpolates between the mean-field Maier-Saupe energy and the continuum Landau-de Gennes energy functional and can describe both spatially homogeneous and inhomogeneous systems. In the mean-field approach the main macroscopic variable, the Q-tensor order parameter, is defined in terms of the second moment of a probability distribution function. This definition imposes certain constraints on the eigenvalues of the Q-tensor order parameter, which may be interpreted as physical constraints. We define a thermotropic bulk potential which blows up whenever the eigenvalues of the Q-tensor order parameter approach physically unrealistic values. As a consequence, the minimizers of this continuum energy functional have physically realistic order parameters in all temperature regimes. We study the asymptotics of this bulk potential and show that this model also predicts a first-order nematic-isotropic phase transition, whilst respecting the physical constraints. In contrast, in the Landau-de Gennes framework the Q-tensor order parameter is often defined independently of the probability distribution function, and the theory makes physically unrealistic predictions about the equilibrium order parameters in the low-temperature regime
Original languageUndefined/Unknown
Pages (from-to)1-11
Number of pages12
JournalMolecular Crystals and Liquid Crystals
Volume525
Issue number1
DOIs
Publication statusPublished - 13 Jul 2010

Keywords

  • eigenvalue constraints
  • elastic constants
  • Landau-de Gennes theory
  • Maier-Saupe
  • nematic liquid crystals

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