A COMPARISON OF LOW-Z EXAFS EXPERIMENT AND AB-INITIO CALCULATIONS

We report high-quality experimental fluorescence-yield EXAFS data and two different types of ab initio simulation (performed with MUFPOT, ICXANES, and FEFF) for O K-edge XAFS of NiO and Cu2O. The results are indicative of the present 'state of the art' of EXAFS simulations for low-Z atoms, including the effects of multiple scattering by the photoelectron. Employing the XAFS simulations to perform a quantitative analysis, the degree of accuracy for the determination of structural parameters, e.g. nearest-neighbour distance, is assessed. It can be agreed that with algorithms now available the problem for standard applications of the treatment of multiple scattering of a photoelectron above the threshold in the commonly used muffin-tin model potential has been solved. This granted, the remaining discrepancies between experiment and calculation disclose the relative significance of refinements to the model other than for the scattering, e.g. Debye-Waller factors, multi-electron effects or corrections to the potential.