The crystallographic information file (CIF): a new standard archive file for crystallography

Abstract

The specification of a new standard Crystallographic Information File (CIF) is described. Its development is based on the Self-Defining Text Archive and Retrieval (STAR) procedure [Hall (1991). J. Chem. Inf. Comput. Sci. 31, 326-333]. The CIF is a general, flexible and easily extensible free-format archive file; it is human and machine readable and can be edited by a simple text editor. The CIF is designed for the electronic transmission of crystallographic data between individual laboratories, journals and databases: it has been adopted by the International Union of Crystallography as the recommended medium for this purpose. The file consists of data names and data items, together with a loop facility for repeated items. The data names, constructed hierarchically so as to form data categories, are self-descriptive within a 32-character limit. The sorted list of data names, together with their precise definitions, constitutes the CIF Dictionary (Core Version 1991). The CIF Core Dictionary is presented in full and covers the fundamental and most commonly used data items relevant to crystal structure analysis. The Dictionary is also available as an electronic file suitable for CIF computer applications. Future extensions to the Dictionary will include data items used in more specialized areas of crystallography.