Theory and Analysis of XAFS

Owing to its element specific and short-range nature, core-level X-ray absorption spectroscopy (XAS) is now routinely used to elucidate the local structural, vibrational, and other physical properties of complex, aperiodic materials. XAS encompasses both extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge spectra (XANES) [1, 2], where the terms refer, respectively, to the structure in the X-ray absorption spectrum μ ω ð Þ at high and low energies relative to the absorption edge with the crossover typically at about 20–30 eV above the edge. The acronym XAFS refers to the fine structure at all energies. The extraordinary capabilities of these spectroscopies come at a price: they depend on comparisons with quantitative simulations of the spectra. Remarkably, however, theories of X-ray spectra have become increasingly accurate and sophisticated, generally overcoming this limitation [2–5].