Hi, Just a quick question... Currently I'm fitting experimental spectra to feff results from two different atomic configurations to try and figure out which scenerio is a better fit and what the ultimate atom positions are.... In doing this I'm already fitting for different sigma^2 for each path (since I'm not dealing with a monoatomic system).... Now I think I would like to fit for each path's individual DelR (....previously I'd been fitting with eta*reff for each but I'm expecting the displacement about the core atom to be quite different than further away from it).... My problem is... I don't have enough independent points to accomodate all the variables given the paths included when fitting over a specific R range. Currently I figure I have at least 2 options: 1)(Assuming I'm already using the largest suitable k-range) -- Increase the r-range for the fit (i.e. if fitting the single scattering paths to 4 Ang requires 18 variables but I only have 15 independent points with r-range 1-4... perhaps increase the r-range 1-4.5 (18 ind. points in this case) or 1-5 (20 ind. points in this case) while still including the paths less than 4Ang in the fit. 2) Lump some of the paths' DelRs into expressions (i.e. having DelRs = eta1*reff, or eta2*reff, or eta3*reff etc for groupings of paths dependent upon distance from core atom). Any suggestions about these ideas, or any other ideas-- I greatly appreciate the input! Thanks a ton! -Kristine