Acta Cryst. (1991). A47, 655-685
The definition of data categories has been given above. Each category represents a major logical group of crystallographic data, such as crystal symmetry, associated chemistry, diffraction data, manuscript text, and so on. Here is a brief introduction to the current CIF data categories. More detailed descriptions are given in the Dictionary (Appendix I).
_audit_ data provide a record of the CIF creation and subsequent updating. These items usually precede all others in the CIF.
_atom_ data are in two separate categories: those that describe atom sites in a crystal structure (i.e. _atom_site_ data names) and those that describe the properties of the atom types that occupy these sites (i.e. _atom_type_ data names).
_cell_ data record the cell parameters, method of measurement, conditions etc.
_chemical_ data specify the composition and chemical properties of the compound. The _chemical_formula_ items must agree with those that specify the density, unit-cell and Z values.
_chemical_conn_ data specify the 2D chemical structure for molecular species.
_computing_ data record the computer programs used in the crystal structure analysis.
_database_ data are only specified by database managers and should only appear in a CIF if they originate from this source.
_diffrn_ data are the diffraction measurements.
_exptl_ data record the crystal measurements, such as density, shape, size etc.
_geom_ data describe the standard molecular and crystal geometry, as calculated from the contents of the _atom_, _cell_ and _symmetry_ data.
_journal_ data are entries used by the journals' staff in processing a CIF.
_publ_ data are used when submitting CIF data to a journal for publication.
_refine_ data describe the structure refinement parameters.
_refln_ and _reflns_ data specify the reflection items used to determine the _atom_ data items. They are in two categories: _refln_ and _reflns_ items. The _reflns_ data specify the parameters that apply to all reflections. The _refln_ data refer to individual reflections and must be included in looped lists. The _reflns_ data items are not looped.
_symmetry_ data specify the space-group symmetry.
On to Looped and non-looped data items
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