Combination of XANES spectroscopy and molecular dynamics to probe the local structure in disordered systems

Individual configurations obtained from molecular dynamics have been combined with the computation of x-ray absorption near-edge structure (XANES) spectra to obtain a theoretical estimation of the spectrum corresponding to a system in a condensed medium lacking long-range order. The influence of the different geometries on the spectrum is studied. The results obtained indicate that the reproduction of the features of the XANES spectrum requires a good sampling of geometrical arrangements. As a test case, an aqueous solution of Cr(H2O)6 3+ was selected, since its simulation reproduces well structural results. The contribution of the second hydration shell on the shape of the spectrum was determined.