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In thermodynamics, a critical point (or critical state) is the end point of a phase equilibrium curve. One example is the liquid–vapor critical point, the end point of the pressure–temperature curve that designates conditions under which a liquid and its vapor can coexist.
Attributes of the resulting crystal depend largely on factors such as temperature, air pressure, cooling rate, and in the case of liquid crystals, time of fluid evaporation. Crystallization occurs in two major steps. The first is nucleation, the appearance of a crystalline phase from either a supercooled liquid or a supersaturated solvent.
Liquid crystal (LC) is a state of matter whose properties are between those of conventional liquids and those of solid crystals.For example, a liquid crystal can flow like a liquid, but its molecules may be oriented in a common direction as in a solid.
The phenomenon is most commonly demonstrated in binary fluid mixtures, such as methanol and cyclohexane.As the critical point is approached, the sizes of the gas and liquid region begin to fluctuate over increasingly large length scales (the correlation length of the liquid diverges).
Crystallization: This is the initial phase where the material to be purified is cooled. As it cools, high-purity crystals begin to form on the cooling surface. The purity is achieved because the impurities tend to remain in the liquid phase rather than being incorporated into the crystal structure.
Crystallography ranges from the fundamentals of crystal structure to the mathematics of crystal geometry, including those that are not periodic or quasicrystals. At the atomic scale it can involve the use of X-ray diffraction to produce experimental data that the tools of X-ray crystallography can convert into detailed positions of atoms, and ...
The term 'crystal engineering' was first used in 1955 by R. Pepinsky [4] but the starting point is often credited to Gerhard Schmidt [5] in connection with photodimerization reactions in crystalline cinnamic acids. Since this initial use, the meaning of the term has broadened considerably to include many aspects of solid state supramolecular ...
Epitaxy can involve single-crystal structures, although grain-to-grain epitaxy has been observed in granular films. [1] [2] For most technological applications, single-domain epitaxy, which is the growth of an overlayer crystal with one well-defined orientation with respect to the substrate crystal, is preferred. Epitaxy can also play an ...