Resonant atomic scattering factor theory: A multiple scattering approach

An approach to the x-ray atomic scattering factor (ASF) calculation is presented on the basis Of multiple-scattering theory, This method allows a first-principles calculation of the ASF in the anomalous dispersion energy region including the influence of the local environment around the resonant atom. Real and imaginary parts of the ASF are obtained in terms of incoming and outgoing polarization vectors for any scattering condition without the use of Kramers-Kronig transformations. The method has been applied, as an example, to the calculation of the anomalous ASF components of Ge, and compared with experimental data taken from bulk crystal reflections and surface reconstruction peaks.