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.