[Ifeffit] Space group type in Artemis

[Bruce Ravel]

On 03/11/2017 05:56 AM, Abhinav Prabhakar wrote:
> Hello,
>
> I have a question about the working of Artemis as a new user.
>
> Artemis does not recognize the space group B11b. When importing a cif
> file of a crystal with this symmetry, it sends a prompt message that the
> space group symbol cannot be recognized. As a result, I changed it to
> P11b and it works. But would this change any crystal information (for
> eg. Degen, Reff values) significantly?

I am not a crystallography expert in any sense.  When I wrote Artemis, I 
meticulously followed what I found in the fourth edition of the 
International Tables for Crystallography, Volume A.  Every symbol 
defined in there is recognized by Artemis.  (Well, I guess I should say 
that every symbol is /supposed to be/ recognized by Artemis.  If one is 
missing,  that's a bug and should be reported.)

"B11b" is not a symbol that I found in my copy of ITC volume A.  As 
Robert suggested, there may be a way to rotate group 9 so that "B11b" is 
an interpretable symbol in the abstract.  But Artemis does not know how 
to do that.  (Nor do I.)

"P11b" is a setting for space group #7.  If, as Robert suggests, your 
CIF file is for space group #9, then the answer to your last question is 
yes.  It is plainly obvious that using a different space group will 
change the degeneracies and distances.


Of course, you did not bother to include a copy of the CIF file in 
question to your original email, so it is not actually possible for 
Robert or I or anyone else to actually help you effectively.

At the risk of sounding like an annoyingly broken record, everyone 
should take the time to ask a good question or write an actionable bug 
report:

   http://bruceravel.github.io/demeter/documents/SinglePage/help.html
   http://bruceravel.github.io/demeter/documents/SinglePage/bugs.html

B


-- 
  Bruce Ravel  ------------------------------------ bravel at bnl.gov

  National Institute of Standards and Technology
  Synchrotron Science Group at NSLS-II
  Building 743, Room 114
  Upton NY, 11973

  Homepage:    http://bruceravel.github.io/home/
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