The X-ray absorption spectroscopy (XAS) is a powerful tool for local atomic structure investigation of materials with different origin including nanocomposites. The extended X-ray absorption fine structure spectroscopy (EXAFS) is very sensitive to the details of local environment of X-ray photon absorbing atom. In order to perform quantitative study of EXAFS data the preliminary calculations of scattering phases and amplitudes of photo-electron in the crystal are required. The quality of this calculation highly affects on precision of such results, such as inter-atomic distances and coordination numbers. An existing methods use iterative self-consisted approach for the estimation of interatomic potential which could be neglected using fixed potential value in interatomic region (“muffin-tin”-zero). The Hedin-Lundqvist exchange potential is commonly used. The paper presents the results of the development and testing of computer code HFampl for the first-principle calculation of scattering phases and amplitudes within “muffin-tin” approximation using exact Hartree-Fock (HF) exchange potential. The development using GNU compilers collection has allowed an execution of the codes in any compatible operating systems (Windows, Linux, Mac). The atomic configurations were prepared for the most elements of the periodic table. The program tests performed on metals, oxides and iron-containing aqueous solutions demonstrated good applicability of the phases and amplitudes for the precise structural analysis, which allows accuracy up to 1% in interatomic distance calculation. Such accuracy in distances determination is as good as accuracy of common program packages. But values of other parameters (such as reduction factor and Debye-Waller parameter) are more realistic in case of application scattering phases and amplitudes obtained with HFampl code.

Keywords: Photoelectron Scattering Phases And Amplitudes For The Determination Of Atomic Structure By EXAFS Spectroscopy