Electronic structure effects on B K-edge XANES of minerals

In order to assess the usability of X-ray absorption near-edge structure (XANES) for studying the structure of BO_n-containing materials, the dependence of theoretical XANES at the B K-edge on the way the scattering potential is constructed is investigated. Real-space multiple-scattering calculations are performed for self-consistent and non-self-consistent potentials and for different ways of dealing with the core hole. It is found that in order to reproduce the principal XANES features it is sufficient to use a non-self-consistent potential with a relaxed and screened core hole. Employing theoretical modelling of XANES for studying the structure of boron-containing glasses is thus possible. The core hole affects the spectrum significantly, especially in the pre-edge region. In contrast to minerals, B K-edge XANES of BPO₄ can be reproduced only if a self-consistent potential is employed.