**Description:**

Data items in the PHASING_SET category record details about the data sets used in a phasing experiment. A given data set may be used in a number of different ways; for instance, a single data set could be used both as an isomorphous derivative and as a component of a multiple-wavelength calculation. This category establishes identifiers for each data set and permits the archiving of a subset of experimental information for each data set (cell constants, wavelength, temperature etc.). This and related categories of data items are provided so that derivative intensity and phase information can be stored in the same data block as the information for the refined structure. If all the possible experimental information for each data set (raw data sets, crystal growth conditions etc.) is to be archived, these data items should be recorded in a separate data block.

Example 1 - based on laboratory records for an Hg/Pt derivative of
protein NS1.
_phasing_set.id 'NS1-96' _phasing_set.cell_angle_alpha 90.0 _phasing_set.cell_angle_beta 90.0 _phasing_set.cell_angle_gamma 90.0 _phasing_set.cell_length_a 38.63 _phasing_set.cell_length_b 38.63 _phasing_set.cell_length_c 82.88 _phasing_set.radiation_wavelength 1.5145 _phasing_set.detector_type 'image plate' _phasing_set.detector_specific 'RXII' |

**Mandatory category:** no

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