Analogy between the twist-bend nematic and the smectic A phases and coarse-grained description of the macroscopic NTB properties
Analogy between the twist-bend nematic and the smectic A phases and coarse-grained description of the macroscopic NTB properties
复制标题
扭转弯曲向列相和近晶A相之间的类比以及宏观NTB特性的粗粒度描述
DOI：
10.1080/02678292.2016.1226972
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发表时间：
2016
期刊：
影响因子：
2.2
通讯作者：
C. Meyer
中科院分区：
文献类型：
--
作者：
Ivan Dozov;C. Meyer
摘要 扭转弯曲向列相 NTB 具有不同寻常的弹性特性。与通常的向列相反，NTB 指向矢 n 会自发扭曲，从而产生小周期和双简并旋向的螺旋结构。迄今为止，已经提出了不同的模型来描述微观尺度上的 NTB 特性，并且仍在积极争论。在宏观尺度上，我们提出了 NTB 和 SmA* 相之间基于对称性的类比。引入复序参数，我们类比 de Gennes 的 SmA* 描述来写出宏观 NTB 能量。通过粗粒化，基于弹性不稳定局部模型，我们用几个类 Frank 弹性系数计算了宏观弹性常数和特征长度。我们讨论了 NTB 相与 SmA* 相比的逆弹性各向异性，及其对 NTB 缺陷结构的影响。我们扩展了粗粒度 (CG) 模型来研究对电场的宏观响应、表面锚定排列和 NTB 相的微观扭曲。最后，我们提出了扭曲晶界相 TGBA 的 NTB 类似物的存在，扭曲场通过 NTB 赝层的螺旋位错网络渗透到块体中。图解摘要
ABSTRACT The twist-bend nematic, NTB, has unusual elastic properties. Contrary to the usual nematic, the NTB director n is spontaneously distorted, resulting in a heliconical structure with small period and doubly degenerate handedness. Different models have been proposed so far, and are still actively debated, to describe the NTB properties on the microscopic scale. On the macroscopic scale, we propose a symmetry-based analogy between the NTB and the SmA* phases. Introducing a complex order parameter, we write the macroscopic NTB energy by analogy with the de Gennes’ SmA* description. By coarse graining, based on the elastic-instability local model, we calculate the macroscopic elastic constants and characteristic lengths in terms of a few Frank-like elastic coefficients. We discuss the inverse elastic anisotropy of the NTB phase, compared with the SmA*, and its impact on the structure of the NTB defects. We extend the coarse-grained (CG) model to investigate the macroscopic response to electric fields, and the surface anchoring alignment and the microscopic distortions of the NTB phase. Finally, we suggest the existence of a NTB analogue of the twist grain boundary phase TGBA, with a penetration of the twist field in the bulk through a network of screw dislocations of the NTB pseudo-layers. GRAPHICAL ABSTRACT
影响因子：
4.9
作者：
C. Präsang;A. Whitwood;D. Bruce
通讯作者：
C. Präsang;A. Whitwood;D. Bruce
影响因子：
3.4
作者：
Goertz, Verena;Southern, Christopher;Goodby, John W.
通讯作者：
Goodby, John W.