[GSAS-II] Clarification on using GSAS 2

[nithya at igcar.gov.in]

Hi,

        This is Dr. Nithya Ravindran from India. I am using GSAS II to extract structural information of double perovskites and I have a couple of doubts to be clarified. They are listed below:

1. After a few iterations of refinement, a stable wR on 1399 observations 15.572% is obtained. Not able to refine further to reduce this value. Visual inspection of the plot of experimental and computed powder diffraction profile agrees well. Can this value be considered acceptable to rely on structural parameters?  We get Chi2 value very high (as high as 3213.91) and GOF 1.53; and RF AND RF2 4.958% AND 9.369% respectively on 12 reflections.  If not, what should be the minimum value of wR for a good fit?

2. in two of the ruthenium and cobalt based double perovskites, Ru and Co exist in +5 and +4 oxidation states respectively. Unable to select these ions as they are not included in the program. Please clarify.

Thank you,
With warm regards,
Nithya
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