中国物理B ›› 2009, Vol. 18 ›› Issue (7): 2885-2892.doi: 10.1088/1674-1056/18/7/044

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Calculating the dielectric anisotropy of nematic liquid crystals: a reinvestigation of the Maier--Meier theory

何军1, 彭增辉1, 宣丽1, 张然2   

  1. (1)State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China; (2)State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China;Graduate School of Chinese Academy of Sciences, Beijing 100039, China
  • 收稿日期:2008-10-19 修回日期:2008-11-24 出版日期:2009-07-20 发布日期:2009-07-20
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos 60578035 and 60736042) and the Science Foundation of Jilin Province of China (Grant Nos 20050520 and 20050321-2).

Calculating the dielectric anisotropy of nematic liquid crystals: a reinvestigation of the Maier--Meier theory

Zhang Ran(张然)a)b), He Jun(何军)a)b), Peng Zeng-Hui(彭增辉)a), and Xuan Li(宣丽)a)†   

  1. a State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China; b Graduate School of Chinese Academy of Sciences, Beijing 100039, China
  • Received:2008-10-19 Revised:2008-11-24 Online:2009-07-20 Published:2009-07-20
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos 60578035 and 60736042) and the Science Foundation of Jilin Province of China (Grant Nos 20050520 and 20050321-2).

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摘要： This paper investigates the average dielectric permittivity (\overline ε ) in the Maier--Meier theory for calculating the dielectric anisotropy (Δε) of nematic liquid crystals. For the reason that \overline ε of nematics has the same expression as the dielectric permittivity of the isotropic state, the Onsager equation for isotropic dielectric was used to calculate it. The computed \overline ε shows reasonable agreement with the results of the numerical methods used in the literature. Molecular parameters, such as the polarizability and its anisotropy, the dipole moment and its angle with the molecular long axis, were taken from semi-empirical quantum chemistry (MOCPAC/AM1) modeling. The calculated values of Δε according to the Maier--Meier equation are in good agreement with the experimental results for the investigated compounds having different core structures and polar substituents.

Abstract: This paper investigates the average dielectric permittivity ($\overline{\varepsilon}$) in the Maier--Meier theory for calculating the dielectric anisotropy ($\Delta \varepsilon$) of nematic liquid crystals. For the reason that $\overline{\varepsilon}$ of nematics has the same expression as the dielectric permittivity of the isotropic state, the Onsager equation for isotropic dielectric was used to calculate it. The computed $\overline{\varepsilon}$  shows reasonable agreement with the results of the numerical methods used in the literature. Molecular parameters, such as the polarizability and its anisotropy, the dipole moment and its angle with the molecular long axis, were taken from semi-empirical quantum chemistry (MOCPAC/AM1) modeling. The calculated values of $\Delta \varepsilon$ according to the Maier--Meier equation are in good agreement with the experimental results for the investigated compounds having different core structures and polar substituents.

Key words: dielectric anisotropy, molecule modeling, semi-empirical quantum chemistry, nematic liquid crystals

中图分类号:  (Permittivity (dielectric function))

  • 77.22.Ch
61.30.Gd (Orientational order of liquid crystals; electric and magnetic field effects on order) 61.30.Cz (Molecular and microscopic models and theories of liquid crystal structure) 61.20.-p (Structure of liquids)