Crystal polymorphism is the existence of different crystal structures for the same chemical substance. Each crystal polymorph can have its own mass density, melting behavior and range of stability on a phase diagram. A different external shape of the same crystal structure alone does not establish a different crystal polymorph.[ref]
polymorph. IUPAC Compendium of Chemical Terminology, fifth edition, entry “polymorph” (15225), definition and Note 2
At fixed temperature and pressure, compare the chemical potentials of the possible crystal polymorphs. The lower value determines the stable bulk thermodynamic phase; equality permits phase coexistence when neither form is beaten by another thermodynamic phase. A higher-chemical potential form can persist through metastability, so finding it in a sample does not by itself locate an equilibrium boundary.
A solid thermodynamic phase with a particular crystal structure, among distinct crystalline forms of the same chemical substance. Crystal polymorphism names the existence of these alternatives; a crystal polymorph names one of the forms.
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In materials science, **polymorphism** refers to the ability of a material to exist in two or more different forms or crystal structures. These different forms can have distinct physical and chemical properties, which can affect the material's behavior in applications. Polymorphism is especially significant in the context of materials like metals, minerals, and polymers. For example: 1. **Metals**: Some metals can adopt different crystal structures depending on temperature or other conditions.
Example:
- the three most table polymorphs of calcium carbonate polymorphs are: