Kleman M, Nastishin Yu A, Malthête J
Laboratoire de Minéralogie-Cristallographie de Paris (UMR7590), T16 case 115, 4 place Jussieu, F-75252 Paris cédex 05, France.
Eur Phys J E Soft Matter. 2002 May;8(1):67-78. doi: 10.1140/epje/i2002-10009-1.
Following our experimental observations of disclination lines in freely suspended droplets and free-standing films (Yu.A. Nastishin et al., Eur. Phys. J. E 5 353 (2001)), topological defects of the twist grain boundary (TGBA) phase are considered according to two aspects: topological and energetical. There are two classes of line defects, disclinations (as in the cholesteric (N*) phase and the liquid vortices phase (NL*), relating to the directors tripod symmetries) and dispirations (relating to the translation-rotation symmetries); there are no topological point defects. Differences between N*, NL* and TGBA disclinations are physical, not topological. The absence of focal conic domains in the TGBA phase is an immediate consequence of the materialization of the helical axis (along the chi-director); the same feature, coupled to the trend to parallelism of the smectic layers, accounts for the predominance of lambda-lines. Finally, the presence of defects akin to developable domains is explained in the frame of the least curvature model, that requires the introduction of a third type of defects: the densities of edge dislocations of the smectic layers.
基于我们对自由悬浮液滴和自支撑薄膜中向错线的实验观察（Yu.A. 纳斯季申等人，《欧洲物理杂志E》5 353 (2001)），从拓扑和能量两个方面考虑了扭曲晶界（TGBA）相的拓扑缺陷。存在两类线缺陷，向错（如在胆甾相（N*）和液晶涡旋相（NL*）中，与指向矢三脚架对称性相关）和位错（与平移 - 旋转对称性相关）；不存在拓扑点缺陷。N*、NL*和TGBA向错之间的差异是物理上的，而非拓扑上的。TGBA相中不存在焦锥畴是螺旋轴（沿χ指向矢）实现的直接结果；同样的特征，再加上近晶层平行趋势，解释了λ线的优势。最后，在最小曲率模型的框架内解释了类似于可展畴的缺陷的存在，这需要引入第三种类型的缺陷：近晶层边缘位错的密度。
