Hello! I have a question concerning the independence of scattering pathways. I fitted the EXAFS signal of a molecule consisting of 30 atoms (the related FEFF calculation is called calc 1). To see the effect of the surrounding solvent molecules in the chi(k) data, I added an O-atom in the coordinate list of the FEFF input file at an arbitrary distance from the absorbing atom (in this case Pt) and I re-ran FEFF (calc 2). As a check within calc 2, I generated the sum of the same scattering paths that were used in the fitting model of calc 1 using the therein obtained structural fit parameters. The new O-atom was not included in this sum. I expected the sum within calc 2 to be identical to the fit of calc 1 based on the fact that the original atoms can not sense the presence of the new O-atom (independence of scattering paths). BUT: the resulting sum was significantly different from the fit! Am I overlooking something here? Aren't the calculated backscatter amplitudes and phases independent from each other? I am using Artemis version 0.8.007, Windows XP, Ifeffit 1.2.9. Thank you! Best regards, Renske Renske M. van der Veen PhD student EPFL / PSI Paul Scherrer Institut Swiss Light Source WSLA/210 5232 Villigen PSI Switzerland Phone: +41 56 310 5362 Fax: +41 56 310 3151 E-mail: renske.vanderveen@psi.ch Web: http://lsu.epfl.ch http://femto.web.psi.ch