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Nematic Liquid Crystal Phase

The simplest liquid crystal phase is called the nematic phase (N). It is characterized by a high degree of long range orientational order but no translational order. Molecules in a nematic phase spontaneously order with their (for calamitic molecules) long axes roughly parallel. A schematic diagram of a nematic phase is shown in Fig. 1.1. An uniformly aligned nematic has a preferred direction, often described in terms of a unit vector called the director, $\mathbf{n}$. More generally a bulk nematic will contain domains. The orientation of the director is constant in each domain but is different in different domains. Viewed under a polarizing microscope the defect regions linking these domains appear as dark threads [5]

Figure 1.1: Schematic diagram of a nematic liquid crystal
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Dr S J Clark