Polymorphism (materials science)
According to EA Mitscherlich, in materials science and mineralogy, polymorphism is the property that a substance can appear in different manifestations ( modifications ). These have the same chemical composition ( stoichiometry ), but differ in the spatial arrangement of the atoms and have different properties. Different structures may be due to influences such as pressure and / or temperature form ( solvothermal ) .
- Graphite , diamond , fullerenes , graphene and cyclo  carbon are modifications of carbon . (Diamond is an insulator while graphite is an anisotropic conductor .)
- α-sulfur, β-sulfur and γ-sulfur are modifications of sulfur .
- White phosphorus, red phosphorus, black phosphorus, and purple phosphorus are modifications of phosphorus .
- Selenium comes in five modifications .
- Tin occurs as α-tin, β-tin and γ-tin ( tin plague ).
- Natural modifications of the silicon dioxide include: a. α- quartz , β-quartz, tridymite and cristobalite occur in nature.
- Aluminum oxide occurs as alumina and corundum .
- Three modifications of calcium carbonate are orthorhombic aragonite , hexagonal vaterite and trigonal calcite .
- Pyrite and marcasite are minerals with different modifications of FeS 2 .
- Three modifications of the aluminum silicate Al 2 SiO 5 are andalusite , thistle and sillimanite .
- Ammonium nitrate (NH 4 NO 3 ) occurs in five modifications.
- The crystalline areas in isotactic polypropylene , a partially crystalline plastic, occur as monoclinic (α-form), pseudohexagonal (β-form) and, under special conditions, triclinic (γ-form) modifications.
- Conversion of the unit cell of iron at certain temperatures: body-centered cubic δ-ferrite, face-centered γ-iron ( austenite ), body-centered cubic α-iron ( ferrite ).
With two modifications one speaks of dimorphism, with three modifications of trimorphism. If a mirror-inverted modification occurs, it is called enantiomorphism .
- Joel Bernstein: Polymorphism in Molecular Crystals , Oxford University Press 2002, ISBN 978-0-19-850605-8 .