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
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Kurt Leinenweber
Department of Chemistry
Arizona State University
Tempe, AZ 85287-1604
Phone: (480)-965-8853
Fax: (480)-965-2747
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-----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
