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Acta Cryst. (1991). A47, 655-685

Data name categories

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.

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