Powder dictionary (pdCIF) version 1.0.1

Category PD_CALIB

Name:
'_pd_calib_[pd]'

Definition:

   This section defines the parameters used for the calibration 
   of the instrument that are used directly or indirectly in the 
   interpretation of this data set. The information in this 
   section of the CIF should generally be written when the 
   intensities are first measured, but from then on should remain 
   unchanged. Loops may be used for calibration information that 
   differs by detector channel. The _pd_calibration_ items, 
   however, are never looped.

Examples:

Example 1.

 
   _pd_calib_std_external_block_id
               QuartzPlate|D500#1234-987|B.Toby|91-15-09|14:02
   _pd_calib_std_external_name
               'Arkansas Stone quartz plate'

Example 2 - 2\q~actual~ = 2\q~setting~ + arctan( cos(P~1~) / {1/[P~0~ (CC - CH~0~ - P~2~ CC^2^)] - sin(P~1~)} ). This allows for the calibration of 2\q for a linear position-sensitive detector (PSD) where the PSD has been set so that the 'centre channel' (CH~0~) is located at 2\q~setting~ as a function of the channel number (CC). In addition to CH~0~, variables P~0~, P~1~ and P~2~ are calibration constants, where P~0~ is the width of a PSD channel in degrees, P~1~ is the angle of the PSD with respect to the perpendicular and P~2~ is a quadratic term for nonlinearities in the detector.

 
    _pd_calibration_conversion_eqn
    ; 2\q~actual~ = 2\q~setting~ + arctan(
      cos(P~1~)/{1/[P~0~ (CC - CH~0~ - P~2~ CC^2^)] - sin(P~1~)})
    ;

Type: null

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Crystallographic Information Framework

Powder dictionary (pdCIF) version 1.0.1

Category PD_CALIB

International Tables for Crystallography

Volume G: Definition and exchange of crystallographic data

Edited by S. R. Hall and B. McMahon

IUCrData