Calculation and interpretation of X-ray spectroscopies with Green’s function multiple scattering theory

Ankudinov, A. L.; Nesvishskii, A.; Rehr, J. J.
May 2000
AIP Conference Proceedings;2000, Vol. 514 Issue 1, p105
Academic Journal
All theories of x-ray based spectroscopies are based fundamentally on quantum electrodynamics (QED), which fully describes the interaction between the electromagnetic field and matter. Since there is no exact solution for the many-body QED Hamiltonian, approximations specific for each particular spectroscopy have been developed separately. Thus for Extended X-ray Absorption Fine Structure (EXAFS) a the scattering potential is well approximated by a superposition of individual atomic electron densities. However this can be a bad approximation near absorption edges, where effects of charge transfer and non spherical potentials can be important. In an attempt to develop a general treatment of x-ray spectroscopies, we have developed an all electron, relativistic, self-consistent real space Green’s function (RSGF) code FEFF8, for multiple-scattering calculations of x-ray absorption, emission, diffraction, etc. Simultaneous, auxiliary calculations of the projected density of states (DOS) are also carried out, which permit an interpretation of the spectra in terms of electronic structure. An illustrative example for Cu anomalous x-ray scattering is also presented, which emphasizes the importance of self-consistency for calculations and interpretation of near-edge data. © 2000 American Institute of Physics.


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