Describes CIF, the data exchange standard of crystallography. Provides: information for scientists who wish to record or use the results of a single-crystal or powder diffraction experiment; the data ontology necessary for designing interoperable computer applications; accompanying software including machine-readable CIF dictionaries, libraries and utility programs.
An essential guide and reference to CIF for programmers, data managers handling crystal-structure information and practising crystallographers.
The measure of absolute structure as defined by Flack (1983). For centrosymmetric structures, the only permitted value, if the data name is present, is 'inapplicable', represented by '.' . For noncentrosymmetric structures, the value must lie in the 99.97% Gaussian confidence interval -3u =< x =< 1 + 3u and a standard uncertainty (e.s.d.) u must be supplied. The _enumeration_range of 0.0:1.0 is correctly interpreted as meaning (0.0 - 3u) =< x =< (1.0 + 3u). Ref: Flack, H. D. (1983). Acta Cryst. A39, 876-881.