Department of physics, Hebei University of Technology, Tianjin 300401, China.
Int J Mol Sci. 2013 Dec 12;14(12):24135-53. doi: 10.3390/ijms141224135.
At the wall in a hybrid nematic cell with strong anchoring, the nematic director is parallel to one wall and perpendicular to the other. Within the Landau-de Gennes theory, we have investigated the dynamics of s = ±1/2 wedge disclinations in such a cell, using the two-dimensional finite-difference iterative method. Our results show that with the cell gap decreasing, the core of the defect explodes, and the biaxiality propagates inside the cell. At a critical value of dc* ≈ 9ξ (where ξ is the characteristic length for order-parameter changes), the exchange solution is stable, while the defect core solution becomes metastable. Comparing to the case with no initial disclination, the value at which the exchange solution becomes stable increases relatively. At a critical separation of dc ≈ 6ξ, the system undergoes a structural transition, and the defect core merges into a biaxial layer with large biaxiality. For weak anchoring boundary conditions, a similar structural transition takes place at a relative lower critical value. Because of the weakened frustration, the asymmetric boundary conditions repel the defect to the weak anchoring boundary and have a relatively lower critical value of da, where the shape of the defect deforms. Further, the response time between two very close cell gaps is about tens of microseconds, and the response becomes slower as the defect explodes.
在具有强锚定的混合向列相液晶盒中，向列型 director 平行于一个壁面而垂直于另一个壁面。在 Landau-de Gennes 理论中，我们使用二维有限差分迭代法研究了此类液晶盒中 s = ±1/2 楔形纹影的动力学。我们的结果表明，随着液晶盒间隙的减小，缺陷的核心会发生爆炸，双轴性会在液晶盒内部传播。在 dc* ≈ 9ξ 的临界值（其中 ξ 是有序参数变化的特征长度）下，交换解是稳定的，而缺陷核心解则变得亚稳。与没有初始纹影的情况相比，交换解变得稳定的临界值相对增加。在 dc ≈ 6ξ 的临界分离下，系统发生结构转变，缺陷核心合并成具有大双轴性的双轴层。对于较弱的锚定边界条件，类似的结构转变发生在相对较低的临界值下。由于受挫减弱，不对称边界条件将缺陷排斥到较弱的锚定边界，并具有相对较低的 da 临界值，其中缺陷的形状发生变形。此外，两个非常接近的液晶盒间隙之间的响应时间约为几十微秒，并且随着缺陷的爆炸，响应变得更慢。
