CIF Archive Format

CIF ARCHIVE FORMAT

The CIF format represents a major step forward in the archiving, publication and communication of crystallographic data. At last it is possible to publish crystal structures and incorporate structural data into the crystallographic databases without the expensive and error-prone retyping of tables by hand. CIF format also provides a convenient method of transferring data from one program system to another. The ACTA instruction instructs SHELXL-93 to write two CIF-format files: 'name.fcf' contains the reflection data and 'name.cif' all other data. These files contain all the items needed for archiving the structure; those answers not known to SHELXL-93 (e.g. the color of the crystal) are left as a question mark. In general the final 'name.cif' file should be edited using any text editor to replace most of these question marks. The file is then suitable for deposition in the CSD (organic) and ICSD (inorganic crystal structure) databases.

For publication via electronic mail it will normally be necessary to add the authors' names, title, text etc., which may also be done in CIF-format; this is followed by the edited contents of one or more '.cif' files each describing one structure (or possibly the same structure at different temperatures etc.). An example of a paper submitted to Acta Cryst. in this way is provided in Appendix D. At the time of writing it is necessary to send the diagram and Fo/Fc tables by post, though in principle the '.fcf' file is suitable for the direct submission of the Fo/Fc data in CIF-format. SHELXL-93 users are strongly recommended to familiarize themselves with the definitive paper by the I.U.Cr. Commission on Crystallographic Data: S.R. Hall, F.H. Allen and I.D. Brown, Acta Cryst., A47 (1991) 655-685.

The auxiliary program CIFTAB is provided with SHELXL-93 to facilitate the transition to CIF. It enables the '.cif' output file from SHELXL-93 to be extended by adding CIF information from other (e.g. diffractometer data processing) programs, and enables a variety of tables to be produced (e.g. crystal data, coordinates, bond lengths and angles, and structure factors) for padding out Ph.D. theses and submission to Journals that have not yet seen the light. Further details of CIFTAB may be found in Appendix C.

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