PSI-SCANS
4.21 - PSI_SCAN absorption correction
Synopsis
This routine uses the method described by
North, Phillips and Mathews , and
is specific for CAD4 data.
Up to 10 psi-scan sets may be processed and the present
implementation has an important restriction in that ALL sets
must contain the SAME number of
measurements for the SAME incremental psi-angles. This is because this data
is averaged in the calculation of the transmission surface.
The psi-scan curve may be Fourier smoothed and specified curves
may be omitted from the averaged transmission surface. A theta (spherical
crystal) correction may also be applied. Graphical output is
provided to display the original psi-data, the averaged psi-curve and
Fourier smoothed psi-curves, and a final comparison between the corrected
and uncorrected data. Once the transmission surface has been adopted, a corrected
reflection file may be written using the Process menu item. If direction cosines
are present in the uncorrected file name.HKL, these will be echoed to
the corrected output file.
NOTE The approximations inherent in the psi-scan method make it unsuitable
for highly absorbing crystals. For these samples a
GAUSSIAN or
ANALTYICAL or
refined absorption correction
should be used.
Files read
- name.INS (for unit cell information only).
- name.HKL - uncorrected reflection file.
- name.PSI (or PSI.DAT) - CAD4 diffractometer file containing psi-scans.
Files written
- PSI_SCAN.HKL - absorption corrected reflection file
- PSI_SCAN.LST - List file giving summary of the applied corrections
- PSI_SCAN.CIF - CIF containing relevant information