Local structure parameters through the fitting of XANES spectra using a multidimensional interpolation: application to the Pd K-edge of Pd-diethynylbiphenyl polymer

A new method of advanced quantitative analysis of x-ray absorption near edge structure (XANES) is described. The method is based on the fitting of experimental XANES data using multidimensional interpolation of the spectra as a function of the structural parameters and full multiple scattering calculations. Such an approach has several advantages in comparison with schemes that existed before, in particular a very small number of ab initio calculations, significant reduction of required computational time, and the possibility to see immediately the spectrum that corresponds to any set of structural parameters. A first application of the method to determine the parameters of the local geometry of a real system, namely Pd-diethynylbiphenyl, is reported. The procedure of polynomial construction is described in detail for this complex of palladium. The best-fit three-dimensional geometry obtained has the following bond distances: Pd-P 2.36 +/- 0.02 angstrom, Pd-C 2.06 +/- 0.02 angstrom and C-C 1.1 +/- 0.03 angstrom, in agreement with results of previous EXAFS studies.