Theoretical study of the origin of x-ray atomic background anomalies by a full-potential multiple scattering approach

Previous extended x-ray absorption fine structure (EXAFS) studies have shown evidence of anomalous contributions in the atomic background function whose origin was debated in the literature. The present study presents advanced multiple scattering calculations aimed to put to a test the existence and origin of the so-called atomic XAFS (AXAFS) contribution, discussed in details in some previous works. We show with specific examples that the muffin-tin approximation normally used in EXAFS calculations is inappropriate to study this phenomenon as spurious oscillations in the atomic background are related to the potential truncation at the border of the muffin-tin spheres. We thus employed a more sophisticated approach beyond the muffin-tin approximation based on the full-potential multiple scattering theory and self-consistent charge densities. The comparison of EXAFS calculations with previous …