A cocrystal is a single crystalline phase containing two or more distinct molecular components in a shared ordered structure. Its components occupy defined roles in the repeating arrangement, rather than simply forming separate crystals mixed together. A stylized arrangement of molecules A and B illustrates the idea without assuming that every cocrystal has that ratio.
Intermolecular forces and molecular geometry influence which combined structure is favorable. A diffraction measurement tests the shared ordering, while a phase diagram distinguishes a stable combined phase from coexistence of separate A-rich and B-rich phases. This is useful because a shared lattice can change properties such as melting behavior and mass density even though the identities of the molecular components remain recognizable. The word describes a structural phase assignment and does not by itself predict which component combinations will form one.
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A cocrystal is a crystalline structure that consists of two or more different components, typically including an active pharmaceutical ingredient (API) and a coformer. These components are typically held together by non-covalent interactions, such as hydrogen bonds, van der Waals forces, or ionic interactions. Cocrystals are characterized by their distinct stoichiometry and can have unique physical and chemical properties compared to their individual components.