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Dear Jens,
I recently prepared a cif-file and came across the same question.
With empirical absorption correction ("_exptl_absorpt_correction_type
empirical") the values for T_min and T_max loose a bit of meaning.
Yet, I took the maximal and minimal values from ABSORP.cbf and scaled
them linearly so that T_max = 1.0 (i.e., I devided the minimal value
by the maximal value and used this as T_min). I your user adds the
'SIZE' to the shelxl ins-file, shelxl writes estimated values to the
cif-output which in my case were much less spread:
_shelx_estimated_absorpt_T_min 0.983
_shelx_estimated_absorpt_T_max 0.997
_exptl_absorpt_correction_type empirical
_exptl_absorpt_correction_T_min 0.447
_exptl_absorpt_correction_T_max 1.000
_exptl_absorpt_process_details 'XDS (Kabsch, 2010)'
I commented under
_exptl_special_details
_exptl_absorpt_correction_T_min and _exptl_absorpt_correction_T_max
from ABSORP.cbf, the absorption factors used by XDS. These are largely
dominated by scale factors, hence the large variation for this
non-cubic crystal shape.
Best,
Tim
On 02/20/2014 11:43 PM, Jens Kaiser wrote:
> All, Sorry, this is a little bit off topic. I could not find a
> thorough definition of the "Correction Factors" for absorption
> correction in XDS nor of the "Transmittance factors" in SADABS. We
> collected small molecule samples on a synchrotron beamline,
> processed the data with XDS and the user now needs to know the
> "Minimum and Maximum T" for their cif. From what I could gather,
> the XDS correction factors in the ABSORP.CBF are multiplied by
> 1000; the values are around 1 (i.e a little smaller /and/ a little
> larger). The cif dictionary for _exptl_absorpt_correction_T_
> states "The permitted range is 0.0 -> 1.0", which clearly has to be
> a different definition.
>
> Any pointers are welcome,
>
> Cheers,
>
> Jens
>
- --
- --
Dr Tim Gruene
Institut fuer anorganische Chemie
Tammannstr. 4
D-37077 Goettingen
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