Numéro |
J. Phys. IV France
Volume 7, Numéro C2, Avril 1997
Proceedings of the 9th International Conference on X-Ray Absorption Fine Structure
|
|
---|---|---|
Page(s) | C2-121 - C2-124 | |
DOI | https://doi.org/10.1051/jp4/1997099 |
J. Phys. IV France 7 (1997) C2-121-C2-124
DOI: 10.1051/jp4/1997099
Non-Local Self-Energy Models for XAS
A.L. Ankudinov and J.J. RehrPhysics Department, Box 351560, University of Washington, Seattle, WA 98195-1560, U.S.A.
Abstract
Ab initio calculations of X-ray absorption spectra (XAS) and its fine structure (XAFS) are dependent
on the many-body exchange and correlation interaction between the photoelectron and the Fermi sea. Non-local
Hartree-Fock (HF) exchange provides a better description of exchange with core electrons while the local density
approximation (LDA) is usually better for valence electrons. The GW approximation for the self-energy Σ provides
a systematic way of joining HF and LDA, using the natural separation of Σ into core and valence parts. This
exchange model is implemented in FEFF7, a new Dirac-Fock based generalization of the FEFF6 code for XAS
calculations. Improvements are found compared with LDA based codes, namely more accurate excitation energies,
phase shifts, amplitudes. These lead to improved near edge calculations and improved distance and coordination
number determinations from XAFS analysis. Spin dependent self-energies and applications to XMCD are also
discussed.
© EDP Sciences 1997