Defects in nematics

J. Dzubiella, M. Schmidt, H. Lowen. Microstructure of topological defects in nematic droplets (submitted). 

The conclusions are consistent with our knowledge of the defects in nematic liquid crystals. 

Points defects are another class of defects in nematic LCs. They occur in droplets and can be also seen in thin capillaries (Fig. 5). The total energy stored in the elastic field around a point defect grows linearly with the radius, R, of the volume enclosed ... 

Point defects are another class of defects in nematics. When a line, such as the wedge disclination of Fig. 3 a, with 5=1, escapes... 

The classification of defects in nematics represents a straightforward example of the applications of homotopic group theory [14, 15], The reader is referred to reviews of the subject [19-21, 23, 52]. This topological approach confirms the absence of walls, the existence of Mobius lines, the mutual annihilation of thin threads and the existence of singular points. More importantly, it shows that defects combine and merge according to the rules of multiplication of the two-element Abelian group Z2. 

Defects in Nematic Main-Chain Liquid Crystalline Polymers... 

Much effort has been devoted to discovering and understanding topological defects in nematic phases, for instance, by controlling the stability of emulsions and interaction between colloidal particles in the elastic ocean of nematic LCs [30,31]. In comparison, little attention has been paid to smectic LCs primarily because... 

A. Sonnet, A. Kilian, and S. Hess, Alignment tensor versus director Description of defects in nematic liquid crystals, Phys. Rev. E 52, 718 (1995). 

Figure 10. Two common defects in nematics, between parallel interfaces, with horizontal anchoring and no preferred orientation, (a, b) Three-dimensional views the director lines, rather than separate segments as in Fig. 15, are represented and lie parallel or normal to the faces of the curved polyhedra. Bend and splay are concentrated in alternating sectors, the twist not being excluded from the bulk, (c, d) Corresponding aspects between crossed polarizers the director lines are not visible under the microscope.

Very large GB systems (over 80,000 molecules) have also been recoitly studied to investigate some of the most distinctive features of liquid crystals topological defects [27,28], until now simulated only with lattice models [29]. In particular, the twist grain boundary phase in smectics [27] and the formation of a variety of defects in nematics by rapid quenching [28] have been examined. 

Certain defects in nematic liquid crystals were discussed in a mathematical way by Oseen [215] in 1933 and later by Prank [91] in 1958. These defects, and others, are described in some detail in Section 3.8. However, not all defects can be adequately described by the classical continuum theory mentioned above, and this led Ericksen [82] to return to the equilibrium theory of nematic liquid crystals in... 

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