Dear Finke,
SADABS and similar programs work best when given scans about several
axes relative to the crystal. Scanning about a single axis can do more
harm than good especially if the symmetry is low. SADABS can also do a
face-indexed numerical absorption correction too, but this assumes that
the crystal is uniformly bathed in the beam, which is unlikely to be the
case with highly focussed beams. Why don't you use the PSI PRIGO
goniometer to scan about several axes?!
Best wishes, George
On 03.03.2015 17:35, Finke Aaron (PSI) wrote:
Dear comrades,
This is slightly off-topic but there are enough experts here to warrant asking.
Here at SLS I occasionally get asked to collect small molecule data on the
synchrotron. By convention, post-refinement corrections for X-ray absorption by
the crystal are required for publication in Acta C and E. XDS, to my knowledge,
does not do this, it just corrects for other absorption sources like air.
Currently, the most popular absorption correction method for small molecules is
the psi-scan correction implemented in programs like SADABS, but I am wondering
if SADABS is appropriate for data collected on a single axis, as most
synchrotron data is. Also, since we use photon-counting detectors (Pilatus),
the other correction options for CCD detectors probably aren’t appropriate
either. I rarely if ever see an improvement in R-factors nor other improvements
in disagreeable reflections after using SADABS from data collected here. What
does everyone think? Is psi-scan appropriate, or should I resort other methods?
Any insights would be much appreciated.
Best regards,
Aaron
------------------------------------------
Dr. Aaron Finke
Postdoctoral Fellow
Swiss Light Source
WSLA/217
CH-5232 Villigen-PSI
phone: +41 56 310 5652
e-mail: aaron.fi...@psi.ch
--
Prof. George M. Sheldrick FRS
Dept. Structural Chemistry,
University of Goettingen,
Tammannstr. 4,
D37077 Goettingen, Germany
Tel. +49-551-39-33021 or -33068
Fax. +49-551-39-22582
