MXAN: a method for the quantitative structural analysis of the XANES energy region

X-ray absorption near-edge structure (XANES) spectroscopy is a powerful method for obtaining local structural and electronic information around a well defined absorbing site of matter in many possible different conditions. the MXAN method allows a complete fit of the XANES energy region in terms of a well defined set of structural parameters. this approach is based on the comparison between experimental data and many theoretical calculations performed by varying selected structural parameters starting from a putative structure, i.e. from a well defined initial geometrical configuration around the absorber. the X-ray photoabsorption cross sections are derived using full multiple-scattering theory, i.e. the scattering path operator is calculated exactly without any series expansion. in this way, the analysis can start from the edge without any limitations in the energy range and polarization conditions. In this chapter, details of MXAN are presented with some new improvements that allow the analysis of time-dependent XANES data and structurally disordered systems.