Introduction to Powder CIF

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Introduction to Powder CIF

A Crystallographic Information File (CIF) is an archive file whose contents and format have been defined and accepted by the world community of crystallographers. Defining such a standard archive file allows for convenient electronic transmission of crystallographic information between different members of a group, laboratories, journals and databases. CIF is a free-format, easily editable archive file constructed to be read by both computer programs and humans. It was adopted in 1991 by the International Union of Crystallography as the standard method to transfer crystallographic data relating to work with single crystals. It was not until 1996 that CIF was extended to include the crystallographic data obtained from Rietveld refinements.

CIF is an ASCII file type that maybe constructed using a word processor, by editing a template file or automatically as an output file by a crystallographic software package. CIF output generation is a common feature of many single crystal refinement programs, but as yet is not so common as an output option from Rietveld refinement programs.

A CIF is constructed using a set of rules governing data names and the corresponding data items, including facilities to loop through common items, such as the fractional coordinates of the atoms within the structure for which the CIF is being produced. The data names are defined in an extensive CIF dictionary that covers data commonly reported in structural work for both single crystal and powder samples. The format is extensible so that data names covering new developements can easily be added. Once a new data name is included it is never removed, as some CIFs written prior to removal would then contain undefined names.

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