Geometrical fitting of experimental XANES spectra by a full multiple-scattering procedure

In this paper a new software procedure is presented, named MXAN, able to fi t the XANES part (from the edge to about 200 eV) of experimental X-ray abso rption data. The method is based on the fitting between the experimental sp ectrum and several theoretical calculations generated by changing the relev ant geometrical parameters of the site around the absorbing atom. The X-ray photoabsorption cross section is calculated using the full multiple-scatte ring scheme; different choices of the exchange correlation part of the pote ntial can be utilised. To show the potentialities of the method the analysi s of the nickel K-edge of the nickel ion in aqueous solution is presented. The procedure is able to recover the correct information on the symmetry an d atomic distances from the experimental Ni K-edge XANES spectrum. The reco vered structure is found to be independent of the starting conditions, show ing the theoretical uniqueness of the structural solution.