Hi,

I wanted to get some advice on a vanadium centered material I’ve been trying to fit for quite a while w/ repeated failure. Based  on XRD and electrochemistry I’m pretty confident in the material/model, and I have the input file for the material.   The first shell out to 2.2 angstroms in R space is a distorted VO6 w/ bond lengths ranging from 1.6 to 2.2 angstroms, similar to the V2O5 which has been discussed on the mailing list recently (July 7^th).  The last two peaks from 2.2 to 3.3 angstroms presumably include 4 V-P and 1 more V-O single scattering paths. (the best fit I could get on the 4V-P/1V-O used only the first of these two peaks.)

With regards to the first shell fitting, is it appropriate to be grouping the V-O bonds in terms of 1 short, 4 medium, and 1 long bond distance to cut down on variables?  I noticed in the V2O5 previously discussed, that he used one ss and delr term for all 6  V-O paths, but I guess that just means making some assumptions that any variations in ss and delr are isotropic throughout.  Is that correct?

I’ve had real issues w/ those peaks representing V-P/V-O from 2-3.3 angstroms so I wonder if it’s unreasonable to try and  extract this information based on the k space or if possible thats not what I have there.   Could it be that I need to account for the two inequivalent V centers?  (In that case, wouldn’t the number of variables be doubled?)      

Thanks for any comments,

Chris