Determination of interatomic distances and coordination numbers by K-XANES in crystalline minerals with distorted local structure

The method for quantitative determination of interatomic distances and coordination numbers (CN) from experimental K-XANES of light metallic atoms in crystalline compounds with distorted local structure is proposed, based on the extraction of the first shell term and the multiple-scattering term. In crystalline minerals the extraction of these terms can be obtained under uncertainties of similar to 0.3-0.4 A in the values of the second and more distant shell radii, using the unambiguous diffraction data on cell unit parameters and the type of point symmetry. The fitting of the extracted first shell term by theoretical terms, generated within alternative models for the split of this shell under the local structure distortions in the environment of the absorbing metallic atom, permits one to obtain the interatomic distances and CN in reasonable quantitative agreement with the diffraction data for the reference compounds studied.