Powder dictionary (pdCIF) version 1.0.1
_pd_block_id is used to assign a unique ID code to a data block. This code is then used for references between different blocks (see _pd_block_diffractogram_id, _pd_calib_std_external_block_id and _pd_phase_block_id). Note that a data block may contain only a single diffraction data set or information about a single crystalline phase. However, a single diffraction measurement may yield structural information on more than one phase, or a single structure determination may use more than one data set. Alternatively, results from a single data set, such as calibration parameters from measurements of a standard, may be used for many subsequent analyses. Through use of the ID code, a reference made between data sets may be preserved when the file is exported from the laboratory from which the CIF originated. The ID code assigned to each data block should be unique with respect to an ID code assigned for any other data block in the world. The naming scheme chosen for the block-ID format is designed to ensure uniqueness. It is the responsibility of a data archive site or local laboratory to create a catalogue of block IDs if that site wishes to resolve these references.