Dear Dr Peter Stephens, Dr. Martin Fisch and Dr. Noberto Masciocchi,
Many thanks for your reply and useful tips.In particularcomments from Dr.
Noberto M. and for sparing time in rearranging my .INP file.
Best regards,
Dr Naveed Zafar Ali
Subject: Re: Site occupancies refinement
Date: Mon, 28 Apr 2014 08:00:50 -0400
From: peter.steph...@stonybrook.edu
To: naveed...@hotmail.com
CC: rietveld_l@ill.fr
You seem to be confusing beq (thermal parameter) with site occupancy. At a
start, I would think that the site would have the same thermal parameter for
either atom, and refine occupancies that sum to unity. For example,
site A1 occ Fe feocc .9 x 0 y 0 z Az .055 beq Abeq 2site A2 occ Ru =1-feocc; x
0 y 0 z =Az; beq =Abeq;will put Fe and Ru in the same site, refine the iron
occupancy (feocc), common z coordinate (Az), and give them the same isotropic
thermal parameter (Abeq).
You could imagine that the lighter atom could have a larger thermal parameter,
but it would be very hard to determine that from powder data because it would
be strongly correlated with site occupancy, etc.
**Peter W. StephensProfessor, Department of Physics and
AstronomyAssociate Dean for Curriculum, College of Arts and Sciences
Stony Brook University(631)
632-8156http://mini.physics.sunysb.edu/~pstephensPlease update your records to
my new email: peter.steph...@stonybrook.edu
On Mon, Apr 28, 2014 at 7:39 AM, NAVEED ZAFAR wrote:
Dear Rietvelders, I was actually doing the site (occupancy) refinement using
TOPAS 4.1 software.While studying the effect of doping on one crystallographic
site.
We normally refine the sites of interest employ the following
methodology.Consider e.g., Pervoskite structure (ABO3) as an example.If we wish
to dope the A site in ABO3,
and to confirm whether doping was successful or not, we normally refinethe
occupancies in the following way.
For example.We refine occupancies like occupancy of original site A =beq1
occupancy of dopant site A`
=1-beq1
If the refinemnent goes well, all the crystallogrhic occupancies should merge
to a single constant value,
those crystallographic sites which are fully occupied should give [occ=1] and
those doped should yield net occupancies [occ (A + A`= 1].
Can anyone share or suggest,why the Beq (isotropic temperature factor) values
are going to huge,??
at the end of such a refinement. Which otherwise should be around [
Beq=Uiso*8pi^2].
Also if possible share .pro file (GUI mode or Launch mode) of such a
refinemnet or some literature.
Best regards,Dr. Naveed Zafar Ali
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