Hi Matthew, I may be biased, but based on what I saw at the recent XAFS13 conference, I would not conclude that the 'international community prefers GNXAS to FEFF' for EXAFS calculations. I think a search of the science citation index would show FEFF to be used somewhat more (say, 10x) than GNXAS. That's not to say that FEFF is better, just that it is in wider use. GNXAS does include both first principles calculations and analysis. It has a very interesting approach for highly disordered systems such as glasses, where a single-shell cumulant expansion is known to be bad. It seems that these sorts of systems (solutions, glasses, etc) are the primary use for GNXAS, though I don't know why that is. In principle, it would be possible to use GNXAS calculations in Ifeffit. Similarly, it would also be possible to use the outputs from EXCURVE (which also does both 'first principle calcs' as well as analysis). I have not pursued either of these, but it's not out of the question. MXAN (which I believe is by M. Benfatto, S. Della Longa, and C. R. Natoli) is a 'full spectrum' XANES analysis program and seems like a nice tool for fitting XANES, including both the white line and first EXAFS oscillations. I've seen it applied (in very nice papers from Benfatto, P. D'Angelo, and others) to ions in solutions and medium- sized biomolecules. I have not seen it applied to EXAFS, and think it may not be appropriate for EXAFS, though I do not know for sure. --Matt