A Brief Introduction to Liquid crystal Physics （简要介绍液晶物理）.pdfVIP

Chapter 1 A Brief Introduction to Liquid crystal Physics A liquid that is interesting due to the order present in it. - A liquid crystal, an oxymoron. The term liquid crystal signifies a state of aggregation that is intermediate between the crystalline solid and amorphous liquid. Liquid crystalline phases appear in the so - called mesogens which are composed of molecules having an anisotropic shape and in- teracting with each other. In the most disordered condensed phase - the isotropic phase - each molecule uniformly explores positions and orientations throughout the whole avail- able space by diffusion mechanisms. In contrast, in the most ordered crystalline phase, the positions of the molecules are fixed in a lattice as are their orientations with respect to this lattice. The simplest example of a mesophase is the nematic phase which appears in systems of elongated molecules tending to orient parallel to each other while showing no positional order, which gives this phase its liquid character. The first subsection of this chapter contains a brief introduction to liquid crystal (LC) physics, which includes an introduction to different types of ordering and their quantifica- tion. Also introduced are the possible interaction among molecules with biaxial symmetry, and their consequences leading to a new (biaxial) phase. The next subsection gives a brief introduction to surface physics and confinement. The last subsection describes the differ- ent models used in the Monte Carlo studies which have been elaborated upon in the later chapters of the thesis. 1 2 Confined Liquid Crystal System 1.1 Phases of Liquid crystal It was only in the end of the year 1888 that the word ‘liquid crystal’ was coined, although for many generations people used them without knowing that as such. In dail