If you don’t
refine the anisotropic displacement parameters, this ”splitting” of Fe/Zn
position
may merely compensate the luck of anisotropic displacements in the model.
*******************************************************
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
*******************************************************
________________________________
From: rajesh thattarathody <rajeshbath...@gmail.com>
To: rietveld_l@ill.fr
Sent: Thursday, June 19, 2014 1:07 PM
Subject: Discrepancy in the atomic coordinates of two isostructural compounds
Dear Rietvelders,
We are trying to refine the structure of InFeO3(ZnO) compound using GSAS. The
compound crystallises in R-3m space group and Zn and Fe occupy the same
position (00 0.2171). This result is obtained from single crystal studies of
isostructural Ga analogue. When we try to refine PXRD of Fe analogue using
these parameters, slight deviations (more than esd) in Fe and Zn positions are
seen (Zn: 0.2190(1) and Fe: 0.2126 (2)). My queries are:
1. Does this mean that x-rays can really distinguish between Fe and Zn
and not Ga and Zn?
2. Is this evidence of any structural ordering in terms of Zn and Fe? Or
even a random placement of Zn and Fe is possible with these deviations?
3. If crystallographically it is not possible, is it acceptable to fix
one’s position based on the other?
thanking you in advance--
Rajesh T
Research Fellow
Catalysis and Inorganic chemistry division
CSIR-National Chemical Laboratory
Pune, India
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