论文标题
电场诱导的列液晶的不稳定性
Electric-Field-Induced Instabilities in Nematic Liquid Crystals
论文作者
论文摘要
使用Oseen-Frank宏观连续理论对涉及磁场或电场的列液晶的系统进行建模，并开发了一般标准以评估平衡溶液的局部稳定性。该标准考虑了电场的不均匀性以及电场和液体晶体主管的相互影响。该标准表明，在所有情况下，与标准参考中的主张相反，不能通过简单地将磁参数替换为相应的电参数来从相似的磁场过渡中获得的电场释放的不稳定性阈值，从而获得类似的磁场转变的公式。这一发现与[Arakelyan，Karayan，Chilingaryan，Sov。物理。 Dokl。，29（1984）202-204]。提供了简单的分析测试，以确定电场诱导的不稳定性何时可能与类似磁场诱导的不稳定性差异。对于我们研究的系统，与磁场类比提供的阈值相比，考虑到电场和导演场之间的完整耦合可以提升或保持不变的不稳定性阈值（永远不要降低IT）。基于提高不稳定性阈值的效果的物理机制是与地面总监场扰动引起的地下电场一阶变化相关的额外自由能。给出了涉及古典Freedericksz过渡以及定期不稳定性的示例。研究了该理论中包含柔韧性术语，发现这些术语无法改变任何经典的Freedericksz跃迁的不稳定性阈值，这与已知的Splay Transitions的结果一致。
Systems involving nematic liquid crystals subjected to magnetic fields or electric fields are modeled using the Oseen-Frank macroscopic continuum theory, and general criteria are developed to assess the local stability of equilibrium solutions. The criteria take into account the inhomogeneity of the electric field and the mutual influence of the electric field and the liquid-crystal director field on each other. The criteria show that formulas for the instability thresholds of electric-field Freedericksz transitions cannot in all cases be obtained from those for the analogous magnetic-field transitions by simply replacing the magnetic parameters by the corresponding electric parameters, contrary to claims in standard references. This finding is consistent with [Arakelyan, Karayan, Chilingaryan, Sov. Phys. Dokl., 29 (1984) 202-204]. A simple analytical test is provided to determine when an electric-field-induced instability can differ qualitatively from the analogous magnetic field-induced instability. For the systems we study, it is found that taking into account the full coupling between the electric field and the director field can either elevate or leave unchanged an instability threshold (never lower it), compared to the threshold provided by the magnetic-field analogy. The physical mechanism that underlies the effect of elevating an instability threshold is the added free energy associated with a first-order change in the ground-state electric field caused by a perturbation of the ground-state director field. Examples are given that involve classical Freedericksz transitions and also periodic instabilities. The inclusion of flexoelectric terms in the theory is studied, and it is found that these terms are not capable of altering the instability thresholds of any of the classical Freedericksz transitions, consistent with known results for splay transitions.
