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Some ways by which crystals form are precipitating from a solution, freezing, or more rarely deposition directly from a gas. 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.
A crystal's crystallographic forms are sets of possible faces of the crystal that are related by one of the symmetries of the crystal. For example, crystals of galena often take the shape of cubes, and the six faces of the cube belong to a crystallographic form that displays one of the symmetries of the isometric crystal system. Galena also ...
Fundamentals of crystallography: crystal systems, Miller Indices, symmetry elements, bond lengths and radii, theoretical density; Crystal and glass structure prediction: Pauling's and Zachariasen’s rules; Phase diagrams and crystal chemistry (including solid solutions) Imperfections (including defect chemistry and line defects) Phase transitions
An example of the cubic crystals typical of the rock-salt structure [broken anchor]. Time-lapse of growth of a citric acid crystal. The video covers an area of 2.0 by 1.5 mm and was captured over 7.2 min. The interface between a crystal and its vapor can be molecularly sharp at temperatures well below the melting point.
A solid solution, a term popularly used for metals, is a homogeneous mixture of two compounds in solid state and having a single crystal structure. [1] Many examples can be found in metallurgy , geology , and solid-state chemistry .
Stacking faults occur in a number of crystal structures, but the common example is in close-packed structures. They are formed by a local deviation of the stacking sequence of layers in a crystal. An example would be the ABABCABAB stacking sequence. A twin boundary is a defect that introduces a plane of mirror symmetry in the ordering of a crystal.
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 ...
A colloidal crystal is an ordered array of colloidal particles and fine grained materials analogous to a standard crystal whose repeating subunits are atoms or molecules. [1] A natural example of this phenomenon can be found in the gem opal, where spheres of silica assume a close-packed locally periodic structure under moderate compression.