reindexing

Joachim Meyer meyer at bio5.chemie.uni-freiburg.de
Sun Nov 6 08:02:41 EST 1994


Dear Neil,

In article <39dgr2$n1k at mserv1.dl.ac.uk>, "Neil Spink" <neil at iris5.icr.ac.uk> writes:
|> I'm trying to reindex some xds data from P212121 to P21212
|> since we are unsure if the h00 reflections are systematically absent
|> or just not collected (no h00 reflections are recorded.)

I use the following recipe to find screw axes in XDS:

1) process the data in a space group with the same point group,
   but without the screw axes (e.g. P222 instead of P212121)

2) XDS produces the file unique.hkl which can be searched for
   the special reflections

3) list all h00 reflections with: (works on any UNIX box)
   awk '$2==0 && $3==0' unique.hkl

   you can count them with:
   awk '$2==0 && $3==0' unique.hkl | wc

   if you are only interested in the reflections larger than 3 sigma:
   awk '$2==0 && $3==0 && $4>3*$5' unique.hkl | wc

4) 0k0 reflections:
   awk '$1==0 && $3==0' unique.hkl

5) 00l reflections:
   awk '$1==0 && $2==0' unique.hkl

This should be a fast and simple way to find systematic extinctions.

*****************************************************************
* Joachim Meyer	 	meyer at bio5.chemie.uni-freiburg.de	*
*			FAX: +49/761/5987			*
*	Abt. Prof. G.E.Schulz					*
*	Institut f"ur Organische Chemie und Biochemie		*
*	Albertstr. 21, D-79104 Freiburg i.Br., Germany		*
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