Polymorphism (materials Science)

Polymorphism (materials Science)

In materials science, polymorphism is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements. The complete morphology of a material is described by polymorphism and other variables such as crystal habit, amorphous fraction or crystallographic defects. Polymorphism is relevant to the fields of pharmaceuticals, agrochemicals, pigments, dyestuffs, foods, and explosives.

When polymorphism exists as a result of difference in crystal packing, it is called packing polymorphism. Polymorphism can also result from the existence of different conformers of the same molecule in conformational polymorphism. In pseudopolymorphism the different crystal types are the result of hydration or solvation. This is more correctly referred to as solvomorphism as different solvates have different chemical formulae. An example of an organic polymorph is glycine, which is able to form monoclinic and hexagonal crystals. Silica is known to form many polymorphs, the most important of which are; α-quartz, β-quartz, tridymite, cristobalite, coesite, and stishovite. A classical example is the minerals calcite and aragonite, both forms of calcium carbonate.

An analogous phenomenon for amorphous materials is polyamorphism, when a substance can take on several different amorphous modifications.

Read more about Polymorphism (materials Science):  Background, Reasons, Ostwald's Rule, Polymorphism in Pharmaceuticals, Interesting Occurrences of Polymorphs, Polytypism

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Polymorphism (materials Science) - Polytypism
... Polytypes are a special case of polymorphs, where multiple close-packed crystal structures differ in one dimension only ... Polytypes have identical close-packed planes, but differ in the stacking sequence in the third dimension perpendicular to the these planes ...