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Liquid Crystalline Ordering in Very Thin System

极薄系统中的液晶有序化

基本信息

批准号：
14540355
负责人：
YAMASHITA Mamoru
金额：
$ 1.09万
依托单位：
Mie University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14540355/
关键词：
nematic phase Maier-Saupe model symmetry breaking potential phase diagram freely suspended film ferroelectric liquid crystals thin liquid crystal cell unstable state 対称破り外場反強誘電性液晶 Potts模型

项目摘要

The orders of liquid crystals are generally soft, and are affected by the boundary conditions. For the system of very thin width, we see the phase change which differs from the one at the bulk system. Due to the inhomogeneity at the walls, the ordering of liquid crystal becomes inhomogeneous. In the present investigation, the inhomogeneity due to wall is described in terms of the fictitious field, and the method to elucidate the phase transitions of the thin system by analyzing the field on the phase diagram of the corresponding bulk system is introduced. On the basis of this theory, the orderings in the very thin nematics and the freely suspended film of ferroelectric smectics are studied.In case the boundary enhances the ordering, the fictitious field is positive, and for the system whose transition is of the second order at the bulk, no phase transition occurs because the singularity is restricted to the zero-field region. In this respect we study the systems whose transitions are of the first order. The ferroelectric smectic phase of material C7 together with the nematic system exhibits the first order phase transition, and both of the systems with very small thickness are studied here.The phase diagram of the nematics is proved to be same topologically to the three-state Potts model, and on the basis of this phase diagram the phase changes under various anchoring conditions are classified. The case of homeotropic anchoring condition is studied in detail, in which unstable phase which never appear in the bulk is shown to appear in the thin system. The freely suspended film of C7 is proved to show the similar unstable phase. For smectics the field versus temperature phase diagram is obtained and general feature of the phase change due to the wall is clarified.

液晶的阶数一般是软的，并且受边界条件的影响。对于非常薄的宽度的系统，我们看到的相变不同于在体系统。由于壁处的不均匀性，液晶的有序性变得不均匀。在本研究中，由于壁的不均匀性描述的虚拟场，并通过分析相应的块体系统的相图上的场来阐明薄系统的相变的方法。在此理论基础上，研究了极薄向列相和自由悬浮铁电近晶薄膜中的有序性，当边界增强有序性时，虚场为正，而对于体相为二阶相变的系统，由于奇异性被限制在零场区，所以不发生相变。在这方面，我们研究的系统的过渡是一阶。C7材料的铁电近晶相和C7系统都表现出一级相变，本文研究了这两个厚度很小的系统，证明了向列相的相图与三态Potts模型在拓扑上是一致的，并在此基础上对不同锚定条件下的相变进行了分类。详细研究了垂面锚定条件的情况，在这种情况下，在薄体系中出现了不稳定相。C7自由悬浮膜也表现出类似的不稳定相。对于近场，得到了场-温度相图，阐明了壁面相变的一般特征。