[Ifeffit] Implementing constraints in EXAFS analysis

[Badari Rao]

Dear Dr. Bruce,
I have collected EXAFS data on a ferroelectric perovskite Sodium Bismuth
Titanate which has an average rhombohedral R3c structure and am trying to
fit the data with R3c as the starting model. But I am having trouble in
implementing constraints for the fit.
I found a paper authored by you, titled "Local structrue and phase
transitions of BaTiO3, Ferroelectrics, 1998, 206-207, pp 407-430". I want
to do similar kind of analysis using Artemis on my data. However, I am
finding difficulty in understanding how the constraints have been
implemented for the refinement of the barium K edge EXAFS, especially those
for the bond lengths (Page 416 in the above mentioned article in particular
is unclear). Could you please explain how the GDS window and the variables
for different paths in this case would look like. Also how do you decide
what parameters to refine and what to keep fixed (table IV in the article)?

Also can you please suggest some literature for beginners which can guide
me in implementing such constraints?

Thanking you,
-- Yours Sincerely,
Badari Narayana. A. R.
Ph.D Student, Nanoscience and Nanotechnology,
c/o Prof Rajeev Ranjan,
Electroceramics Lab,
Department of Materials Engineering,
Indian Institute of Science.
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