Progress in the theory and interpretation of XANES

There has been substantial progress in recent years, both in the theory and in ab initio codes for calculations of X-ray absorption spectra (XAS), and in particular, the near edge structure (XANES). This progress is a sequel to the successful development of the theory and interpretation of extended X-ray absorption fine structure (EXAFS). Here, we review the progress in this field leading up to the current state. We focus on the real-space multiple scattering (RSMS) approach which gives a unified treatment of both EXAFS and XANES, as well as many other spectroscopies. We also discuss the close connection between RSMS theory and excited state electronic structure, and in particular, corrections to the independent particle approximation which are essential in a quantitative theory. These developments have led to a number ab initio codes for the calculation and interpretation of XAS in terms of the electronic structure and coordination chemistry of materials.