对向列相液晶反转壁中+1缺陷处挠曲电效应的理论分析

基于Pramoda Kumar等人文章中关于向列相液晶反转壁中+1缺陷处挠曲电效应的实验现象，我们利用Landau-de Gennes理论给出相应的理论分析。当对弱锚定的平行排列向列相液晶盒施加垂直基板的直流电压，在反转壁中的±1缺陷会发生旋转。对于其中的+1缺陷，我们给出了外加电场作用下液晶分子的自由能表达式并通过模拟描述指向矢的方位角和极角的变化情况给出相应的缺陷处电场驱动的结构变化。模拟结果给出的挠曲电效应引起的方位角的变化角度与Pramoda Kumar等人的实验得到的在+1缺陷处消光刷的变化情况是一致的。

Theoretical analysis of the influence of flexoelectric effect on the +1 defect site in nematic inversion walls

Based on the experimental phenomena of flexoelectric response at defect sites in nematic inversion walls conducted by Pramoda Kumar et al., we gave the theoretical analysis using the Landau-de Gennes theory. When a direct-current electric field normal to the plane of substrate is applied to the parallel aligned nematic liquid crystal cell with weak anchoring, the rotation of ±1 defects in the narrow inversion walls can be exhibited. The free energy of liquid crystal molecules around the +1 defect site was formulated and the electric field driven structural changes at the defect site characterized by polar and azimuthal angles of the local director were simulated. The results reveal that the deviation of azimuthal angle induced by flexoelectric effect are consistent with the switching of extinction brushes at the +1 defect obtained in the experiment conducted by Pramoda Kumar et al.