Hi Francisco, Your script, or (to simplify for the discussion) path(1, file=feff0001.dat, s02 = 0.9, sigma2 = 0.002) path(2, file=feff0002.dat, s02 = 0.9, sigma2 = 0.002) path(3, file=feff0003.dat, s02 = 0.9, sigma2 = 0.002) ff2chi(1-3, group=mycalc) fftf(mycalc.chi, kmin=1, kmax=15, dk=0.5, kweight=2.0, kwindow='hanning') will generate arrays of data for mycalc.k, mycalc.chi. The fftf() command will then generate arrays mycalc.r, mycalc.chir_mag, mycalc.chir_re, and so on for the Fourier transform. I think you're expecting the ifeffit ff2chi() command to write out a file, as Feff's ff2chi module does. IFeffit is meant to be a bit more flexible than that, so you'd have to explicitly write out the file yourself. The benefit of this is that you can sum components from different Feff calculations, could write out k-weighted chi(k), or even components of chi(R) as easily as you can write out chi(k). Adding something like write_data(file=my_chik.dat, mycalc.k, mycalc.chi) write_data(file=my_chir.dat, mycalc.r, mycalc.chir_mag, mycalc.chir_re) to your script would do this. Or, as you also say, you can use Feff's ff2chi module. Hope that helps, --Matt