1.2 Information Content of the Cambridge Structural Database
The CSD records bibliographic, 2D chemical and 3D structural results from
crystallographic analyses of organics, organometallics and metal complexes.
Both X-ray and neutron diffraction studies are included for small and
medium-sized compounds containing up to ca. 500 atoms (including hydrogens).
The CSD is fully retrospective and is updated on a current basis. About 12,000
new entries were added in 1993. All information is abstracted from the primary
literature and associated supplementary publications; the CCDC acts as the
official depository for unpublished coordinate information for over 30
journals. All information entering the CSD is subject to computerized check
and evaluation procedures.
A CSD entry relates to an individual publication of a specific crystal
structure: papers reporting n crystal structures will generate n CSD entries.
Each CSD entry is identified by a CSD Reference Code (refcode) which identifies
the chemical compound (six letters) and its publication history (two additional
The second digit identifies supplementary studies of the compound e.g. by a
different research group, in a different polymorph, by different radiations, at
different temperatures, etc.
The first digit refers to the publication history of each study by a given
research group: zero indicates the initial paper, maybe a short note, 1, 2 ....
indicate later publications of the same supplementary study.
It is convenient (Figure 1) to categorize the information content of the CSD
1D Information: Text and Simple Numerical Items
2D Information: Chemical Structural Diagram as a Connection
- Bibliographic Items compound name, journal reference, etc.
- Chemical Text Strings molecular formula, amino-acid sequences.
- Simple Numerical Items unit-cell parameters, R-factor, etc.
- Text Comment describing e.g. disorder, errors, etc.
- Atom properties atom sequence number, element symbol, no. of connected
non-H atoms, no. of terminal H atoms, net charge, 2D display coordinates.
- Bond properties pair of atom sequence numbers and formal chemical bond
type [1=single, 2=double, 3=triple, 4=quadruple, 5=aromatic, 6=catena bond,
7=delocalized double, 9=pi-bond, positive bond types are acyclic, negative ones
3D Information: Crystal Structure Description
Since October 1993, information from the Protein Data Bank is being formatted
for inclusion in the CSD files. The current status of this work, and the
search facilities currently provided, are detailed in Section 3.7 of this
Guide. Future developments in this area will be announced through the on-line
documentation in the CSD System and through Newsletters issued periodically by
- Space-Group and Symmetry Operators.
- 3D Atomic Coordinates (Fractional) for Crystal Chemical Unit (see Section
- Crystallographic Connectivity established using Covalent Radii.
- Matching Information that maps the 'crystallographic' atoms to 'chemical'
atoms in the 2D connection table (see Section 1.3).