Université Montpellier 2, Laboratoire Charles Coulomb UMR 5221, Montpellier, France.
Phys Rev Lett. 2011 Jun 17;106(24):247802. doi: 10.1103/PhysRevLett.106.247802. Epub 2011 Jun 15.
We study the nematic-smectic phase transition of a thermotropic liquid crystal confined to a spherical shell. Far from the nematic-smectic phase transition temperature, T(NS), we observe a configuration with four +1/2 defects, as predicted by theory. Since in this case K(1)≈K(3), the four defects are confined at the thinnest part of the shell to minimize the energy associated with the defect cores. By contrast, near T(NS), where K(3)≫K(1), bend distortions become prohibited and the defects organize themselves along a great circle of the sphere, confirming recent theoretical and simulation results. During this structural change, the defects associate in two pairs that behave independently. In the smectic phase, we observe a new configuration displaying curvature walls.
我们研究了热致液晶在球形壳内的向列-层状相转变。在远离向列-层状相转变温度 T(NS)的情况下，我们观察到了一种具有四个 +1/2 缺陷的构型，这与理论预测相符。由于在这种情况下 K(1)≈K(3)，因此四个缺陷被限制在壳的最薄部分，以最小化与缺陷核心相关的能量。相比之下，在接近 T(NS)的情况下，K(3)≫K(1)，弯曲变形受到限制，缺陷沿着球体的大圆周组织起来，这证实了最近的理论和模拟结果。在这个结构变化过程中，缺陷以两对独立的形式结合在一起。在层状相中，我们观察到了一种新的具有曲率壁的构型。
