混合排列向列相液晶薄盒中–1/2向错引起的有序重构的扩散

基于Landau-de Gennes理论, 利用松弛迭代法, 研究了混合排列向列相液晶薄盒中–1/2向错引起的有序重构的扩散现象, 给出了–1/2向错的核结构、双轴性结构, 以及盒厚减小时有序重构的扩散. 当盒厚小于15ξ时, 随着盒厚的减小, 向错范围和有序重构区域沿基板方向迅速扩散; 当盒厚减小到临界厚度10ξ时, 有序重构的范围扩散到整个液晶盒中, 以向错中心所对应的平面为界, 指向矢一部分垂面排列, 另一部分沿面排列. 本文的研究对拓扑缺陷对向列相液晶中的亚微米胶体粒子的调节作用具有一定的理论指导意义. 关键词： 混合排列向列相液晶薄盒 –1/2向错 有序重构扩散 松弛迭代法     

Bound particle with magnetic moment in a space with topological defect

We consider a bounded quantum mechanical particle with spin ?1/2 and a gyromagnetic ratio g, which is placed in a uniform magnetic field, in a space with a linear topological defect. We obtain the exact expressions for eigenfunctions and eigenvalues, using the approach of the continuum theory of defects, and show the dependence on the topological parameters and potential harmonic. Besides, we study the limits case and obtained the results described in the literature. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Effect of Disclination Lines on Free Energy of Nematic Liquid Crystals

In the light of φ-mapping method and topological current theory, the effect of disclination lines on the free energy density of nematic liquid crystals is studied. It is pointed out that the total Frank free energy density can be divided into two parts. One is the distorted energy density of director field around the disclination lines. The other is the saddle-splay energy density, which is shown to be centralized at the disclination lines and to be topologically quantized in the unit of kπ /2 when the Jacobian determinant of the director field does not vanish at the singularities of the director field. The topological quantum numbers are determined by the Hopf indices and Brouwer degrees of the director field at the disclination lines, i.e., the disclination strengthes. When the Jacobian determinant vanishes, the generation, annihilation, intersection, splitting and merging processes of the saddle-splay energy density are detailed in the neighborhoods of the limit points and bifurcation points, respectively. It is shown that the disclination line with high topological quantum number is unstable and will evolve to the low topological quantum number states through the splitting process.     

Kinetics of Grain Boundary Recovery in Deformed Polycrystals

Annealing kinetics are studied for nonequilibrium ensembles of dislocations occurring in grain boundaries during plastic deformation. Two types of dislocation ensembles are considered: 1) walls of sessile extrinsic grain boundary dislocations (EGBDs), which cause a change of the GB misorientation angle, and 2) arrays of glissile EGBDs having a Burgers vector tangential to the grain boundary plane. For both types similar exponential relationships are obtained for the relaxation of the average EGBD density, with approximately the same characteristic time proportional to the cube of grain size.     

The solution of a wedge disclination dipole interacting with an annular inclusion and the force acting on the disclination dipole

The interaction between a wedge disclination dipole and an elastic annular inclusion is investigated. Utilizing the Muskhelishvili complex variable method, the explicit series form solutions of the complex potentials in the matrix and the inclusion region are derived. The image force acting on the disclination dipole centre is also calculated. The influence of the location of the disclination dipole and the thickness of the annular inclusion as well as the elastic dissimilarity of materials upon the equilibrium position of the disclination dipole is discussed in detail. The results show that a stable equilibrium point of the disclination dipole near the inclusion is found for certain combinations of material constant. Moreover, the force on the disclination dipole is strongly affected by the position of the disclination dipole and the thickness of annular inclusion. The repulsion force increases （or the attraction force reduces） with the increase of the thickness of the annular inclusion. An appropriate critical value of the thickness of the annular inclusion may be found to change the direction of the force on the disclination dipole. The present solutions include previous results as special eases.     

Topological Aspect and Bifurcation of Disclination Lines in Two—Dimensional Liquid Crystals

Using φ-mapping method and topological current theory,the topological structure and bifurcation of disclination lines in two-dimensional liquid crystals are studied.By introducing the strength density and the topological current of many disclination lines,the total disclination strength is topologically quantized by the Hopf indices and Brouwer degrees at the singularities of the director field when the Jacobian determinant of director field does not vanish.When the Jacobian determinant vanishes,the origin,annihilation and bifurcation processes of disclination lines are studied in the neighborhoods of the limit points and bifurcation points,respectively.The branch solutions at the limit point and the different directions of all branch curves at the bifurcation point are calculated with the conservation law of the topological quantum numbers.It is pointed out that a disclination line with a higher strength is unstable and it will evolve to the lower strength state through the bifurcation process.     

Molecular simulations of entangled defect structures around nanoparticles in nematic liquid crystals

We investigate the defect structures forming around two nanoparticles in a Gay–Berne nematic liquid crystal using molecular simulations. For small separations, disclinations entangle both particles forming the figure of eight, the figure of omega and the figure of theta. These defect structures are similar in shape and occur with a comparable frequency to micron-sized particles studied in experiments. The simulations reveal fast transitions from one defect structure to another suggesting that particles of nanometre size cannot be bound together effectively. We identify the ‘three-ring’ structure observed in previous molecular simulations as a superposition of the different entangled and non-entangled states over time and conclude that it is not itself a stable defect structure.     

端基含12个己氧基偶氮苯介晶基元的树状碳硅烷液晶的合成

用发散法合成了周边含12个己氧基偶氮苯介晶基元(M3)端基的树状碳硅烷(D1),并用元素分析、氢谱、激光质谱、红外光谱、紫外-可见光谱、偏光显微镜、DSC和WAXD对产物进行表征.结果表明,D1为向列相,与M3相同,树状物相态由介晶基元相态决定,D1的液晶态相行为:K92N126I124N78K,D1熔点比M3降低了24～30℃,D1清亮点比M3提高了6～8℃,D1液晶态温区比M3加宽30～38℃,在树状物中观察到S=+2的高强向错.     

ELASTIC INTERACTION BETWEEN WEDGE DISCLINATION DIPOLE AND INTERNAL CRACK

The system of a wedge disclination dipole interacting with an internal crack was investigated. By using the complex variable method, the closed form solutions of complex potentials to this problem were presented. The analytic formulae of the physics variables, such as stress intensity factors at the tips of the crack produced by the wedge disclination dipole and the image force acting on disclination dipole center were obtained. The influence of the orientation, the dipole arm and the location of the disclination dipole on the stress intensity factors was discussed in detail. Furthermore, the equilibrium position of the wedge disclination dipole was also examined. It is shown that the shielding or antishielding effect of the wedge disclination to the stress intensity factors is significant when the disclination dipole moves to the crack tips.     

含邻位羟基Schiff碱近晶相液晶中的高强向错

含邻位羟基Ｓｃｈｉｆｆ碱近晶相液晶中的高强向错张其震，崔利，孙继润（山东大学化学院，济南，２５０１００）关键词高强向错点，近晶相纹影织构，液晶纹影（Ｓｃｈｌｉｅｒｅｎ）是向列相液晶织构的常见形式，某些近晶相液晶也可出现纹影织构，其特征为以消光黑点为中...