含偶极矩的V形液晶分子系统的相变  

Phase Transitions of Liquid Crystal System Consisted by V-Shaped Molecules with Dipole Moments

作　　者：白林玉[1] 刘红[1] 

机构地区：[1]南京师范大学物理科学与技术学院,江苏南京210023

出　　处：《液晶与显示》2013年第5期661-667,共7页Chinese Journal of Liquid Crystals and Displays

基　　金：江苏省科技厅项目(No.BK2009399)

摘　　要：文章中考虑了一带有电偶极矩的V形液晶分子系统,假设液晶分子长棒间的简单相互作用以及电偶极矩间的相互作用形式,利用平均场理论,得到含电偶极矩的V形液晶分子系统在电偶极矩间相互作用强度(v_0)和温度(t)平面内的相图,以及在V形液晶分子间夹角(α)和温度平面内的三类相图。结果表明,在v_0-t平面内的相图曲线中,存在由各向同性相经一级相变直接进入双轴向列相的Landau曲线;而在α-t平面内的第一类相图曲线中,当v_0较小时,不存在Landau曲线;在第二类相图中(v_0较大时),在合适的电偶极矩相互作用强度和分子间夹角的范围内,系统的相变曲线中才会出现Landau曲线;在第三类相图中(v_0最大时),相图特征则与第二类相图相反。The phase transitions of liquid crystal system consisted by V-shaped molecules with dipole moments are studied in this paper. Based on a simple interaction energy between rigid molecules and interaction energy between dipoles, the phase diagrams in the plane of interaction strength between dipoles （v0） and temperature （t） are obtained by mean-field theory. Three types of phase diagrams in the plane of the angle （α） of the V-shaped molecules and temperature are also obtained. The results show that in the v0-t plane, decreasing temperature can make the isotropic phase entering into biaxial nematic phase by the first order transition, therefore Landau curve exists. In the α-t plane, the first type of phase diagram shows that, while v0 is relatively small, Landau curve does not exist. Yet, in the second type of phase diagram, where v0 is larger, only for appropriate interaction strength and in the appropriate range of values, can Landau curve exist. In the third type where v0 is the largest, the feature of the phase diagram is the opposite of the feature of the second type.

关 键 词：双轴向列相 相变 V形液晶分子 

分 类 号：O753.2[理学—晶体学]