[cctbxbb] reflection conditions for non-standard settings

Petrus Zwart phzwart at lbl.gov
Sat Jun 4 13:12:43 PDT 2011

This could be of use perhaps:


I use it in xtriage for spacegroup determination. I'm not sure what your
application is you have in mind, it might nit be suitable of course.


Verstuurd vanaf mijn iPhone

Op Jun 4, 2011 om 13:04 heeft "Ralf W. Grosse-Kunstleve" <rwgk at yahoo.com>
het volgende geschreven:

Hi David,

cctbx does not include lists of reflection conditions as you find them in
the International Tables.

It is very easy and fast to derive the reflection condition for a given hkl
directly from the symmetry operations. See the code near the top of
cctbx/sgtbx/miller.cpp. This is what we use for all practical applications.
For example:

  from cctbx import sgtbx
  sg = sgtbx.space_group_info("19").group()
  print sg.is_sys_absent((1,2,3))
  print sg.is_sys_absent((0,0,3))

 I have C code given to me by Maxim Larine and Slava Klimkovich in 1997
which computes the conditions, but it involves inefficient grid searches.

I think a good solution would be to tabulate the conditions for the 230
reference settings and figure out the transformation law to obtain the
conditions for arbitrary settings via a change of basis. But I yet have
to find a practical motivation for spending the effort implementing this.

If you find that Phil has a solution, it would be nice to move it into


*From:* David Waterman <dgwaterman at gmail.com>
*To:* cctbxbb at phenix-online.org
*Sent:* Saturday, June 4, 2011 3:28 AM
*Subject:* [cctbxbb] reflection conditions for non-standard settings


I'm new to cctbx and to this mailing list, so please let me first apologise
if the answer to this question should be obvious, or lies in the archive.

I want a list of general reflection conditions for all space groups and
settings listed in the CCP4 file syminfo.lib. At first I thought I could get
this information from the online version of ITC vol A, but I soon realised
that only certain standard settings are included. To avoid deriving them all
by hand from the symop and cenop lines, I wonder if there is a foolproof way
I can get this information from cctbx, but I don't know where to begin.
Perhaps something in sgtbx?

Many thanks

-- David

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