Section 3.3.4.4. Observations and measurement conditions

The data items in these categories are as follows:

(a) Part of PD_DATA

(b) PD_MEAS_INFO

(c) PD_MEAS_METHOD

The arrow () is a reference to a parent data item.

The item _pd_data_point_id identifies each entry in the list of measured, processed or simulated intensities. It is the only item in the PD_DATA category that actually begins with the string _pd_data_, and is included here for convenience. If the list of intensities is split across several distinct loops, the role of this identifier may be adopted by other identifiers, such as _pd_meas_point_id in an isolated list of measured intensities.

The _pd_meas_* data items contain unprocessed measurements and documentation on the instrumental settings used for the measurements. Note that the choice of the data items used to represent this information is determined by the type of diffraction instrument, as well as how the measurement was conducted. This will be discussed further in Section 3.3.8. However, some _pd_meas_* data items are independent of the instrument type. For example, the use of _pd_meas_datetime_initiated is good practice, as is use of the _pd_meas_info_author_* data items. It is probably good practice to record the number of data points in _pd_meas_number_of_points for the benefit of people who might read the CIF, but there is no requirement that this item be present. This means that software should determine the number of data points directly when reading the CIF, rather than relying on the presence of a value for _pd_meas_number_of_points.