Yes, but the atom doesn't have to sit there, unlike in the case of 2/m. So,
GSAS has to fix z for one atom...
I don't have my International Tables with me, please correct me if I'm wrong
(there should be no sites with a fixed z parameter in P2/n).
- Kurt
-------
Kurt Leinenweber
Department of Chemistry
Arizona State University
Tempe, AZ 85287-1604
Phone: (480)-965-8853
Fax: (480)-965-2747
-------
-----Original Message-----
From: Magnus H. Sørby [mailto:[EMAIL PROTECTED]
Sent: Wednesday, March 31, 2004 12:24 AM
To: [EMAIL PROTECTED]
Stephen and Kurt,
P2/n has a 2-fold axis perpendicular to a glide plane, so it does have fixed
points (unlike e.g. R3c).
Best regards,
Magnus H. Sørby
> -----Opprinnelig melding-----
> Fra: Kurt Leinenweber [mailto:[EMAIL PROTECTED]
> Sendt: 31. mars 2004 08:55
> Til: [EMAIL PROTECTED]
> Emne: Defining the origin of P2/n
>
>
> Stephen,
>
> I think that P2/n has no fixed points, and in order to keep the whole
> structure from shifting along the c-axis, one of the atoms has to be
> arbitrarily fixed. GSAS automatically fixes the first atom
> z-parameter (was
> your atom on the 2-fold symmetry axis?). I remember this from
> refining the
> structure of high pressure FeTiO3 which had space group R3c.
>
> - Kurt
>
>
> -------
>
> Kurt Leinenweber
> Department of Chemistry
> Arizona State University
> Tempe, AZ 85287-1604
>
> Phone: (480)-965-8853
> Fax: (480)-965-2747
>
> -------
>
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
> Sent: Tuesday, March 30, 2004 11:03 PM
> To: [EMAIL PROTECTED]
>
>
> Dear Rietvelders,
>
> I used GSAS to refine my structure in P2/n, however the program
> automatically
> fixed the the XYZ positions of the first atom during refinement. To my
> surprise, this atom is not seen in the "fixed atom list" in the atom
> parameters
> menu of GSAS.
>
> Please advise and many thanks,
>
> stephen
>
>
>
>
>
