Many-pole model of inelastic losses applied to calculations of XANES

Abstract

Conventional Kohn-Sham band-structure methods for calculating deep-core X-ray spectra typically neglect photoelectron self-energy effects, which give rise to an energy-dependent shift and broadening of the spectra. Here an a posteriori procedure is introduced to correct for these effects. The method is based on ab initio calculations of the GW self-energy using a many-pole model and a calculation of the dielectric function in the long wavelength limit using either the FEFF8 real-space Green's function code, or the AI2NBSE interface between the National Institute of Standards and Technology (NIST) Bethe-Salpeter equation solver (NBSE) and the ABINIT pseudopotential code. As an example the method is applied to core level X-ray spectra of LiF and MgAl2O 4 calculated using (respectively) OCEAN, an extension of the AI2NBSE code for core level excitations, and the PARATEC pseudopotential code with the core-hole treated using a super-cell. The method satisfactorily explains the discrepancy between experiment and calculations. © 2009 IOP Publishing Ltd.