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Powder dictionary (pdCIF) version 1.0.1

Category PD_DATA

Name:
'_pd_data_[pd]'

Definition:

   The PD_DATA category contains raw, processed and calculated
   data points in a diffraction data set. In many cases, it is
   convenient to tabulate calculated values against the
   raw and processed measurements, and so the various
   _pd_meas_, _pd_proc_ and _pd_calc_ data items belonging
   to this category may be looped together. In some instances,
   however, it makes more sense to maintain separate tables of
   the data contributing to the measured and processed
   diffractograms (for example, a profile may be calculated
   at 2theta values different from those of the measured
   data points). To facilitate the identification of equivalent
   points in these separate tables, separate identifiers are
   defined.

Examples:

Example 1 - data set collected for a two-phase sample (Al~2~O~3~/Si) by B. H. Toby, '1997-01-29T16:37|POWSET_01|B.Toby|..NIST-D5000'. 
 
    loop_
      _pd_data_point_id
      _pd_meas_intensity_total
      _pd_proc_ls_weight
      _pd_proc_intensity_bkg_calc
      _pd_calc_intensity_total
    1    240(15)       0.00417     214.5   214.5 
    2    219(15)       0.00457     214.3   214.2 
    3    206(14)       0.00485     214.0   214.0 
    4    212(15)       0.00472     213.8   213.7 
    5    190(14)       0.00526     213.5   213.5 
    6    203(14)       0.00493     213.2   213.2 
     # - - - - data truncated for brevity - - - -


Example 2 - the data of Example 1 split into three separate tables. 
 
     loop_
      _pd_meas_point_id
      _pd_meas_intensity_total
    1  240(15) 2  219(15) 3  206(14) 4  212(15) 5  190(14) 6  203(14)

     loop_
      _pd_proc_point_id
      _pd_proc_ls_weight
      _pd_proc_intensity_bkg_calc
    1  0.00417  214.5      2  0.00457  214.3
    3  0.00485  214.0      4  0.00472  213.8
    5  0.00526  213.5      6  0.00493  213.2

     loop_
      _pd_calc_point_id
      _pd_calc_intensity_total
    1   214.5 2   214.2 3   214.0 4   213.7 5   213.5 6   213.2


Example 3 - hypothetical example where the measured and calculated points are not in one-to-one correspondence. 
 
   loop_ 
     _pd_meas_point_id
     _pd_meas_2theta_scan
     _pd_meas_intensity_total
            1  21.0   24
            2  21.2   32
            3  21.4   67
            4  21.6   98

   loop_ 
     _pd_calc_point_id
     _pd_proc_2theta_corrected
     _pd_calc_intensity_total
            1   21.0  26
            1a  21.3  56
            4   21.6  76
            4a  21.9  90


Type: null

Category: category_overview


International Tables for Crystallography

Volume G: Definition and exchange of crystallographic data

First online edition (2006)

Edited by S. R. Hall and B. McMahon

An essential guide and reference to CIF for programmers, data managers handling crystal-structure information and practising crystallographers.