PLATON Manual

Molecules and Residues


The concepts of molecules and residues are related but not always synomymous within the PLATON realm. A residue is defined as a part of the structure that is connected by intra-molecular bonds only and is associated with a number. A structure may thus contain one or more residues. Residues may be chemically equivalent or chemically distinct. A molecule is defined as an asymmetric part of the structure connected by intra-molecular bonds only. Several molecules may join by crystallographic symmetry into one residue. A particular molecule is designated by a code: [nijk.rr] where n denotes the symmetry operation with respect to the basic molecule, ijk the translation with respect to 555 and rr the residue number. The structure of sucrose thus consists of two molecules (e.g. [1555.01] and [2545.01]) but only one residue.