Model Extended X-ray Absorption Fine Structure (EXAFS) Spectra from Molecular Dynamics Data for Ca 2+ and Al 3+ Aqueous Solutions

Theoretical extended X-ray absorption fine structure (EXAFS) spectra have been computed from molecular dynamics (MD) simulation data. Based on MD-generated molecular geometries, EXAFS spectra were generated with the FEFF6 program, commonly used in the analysis of experimental EXAFS spectra. The effects of multiple scattering and second-shell neighbors on the theoretical spectra were evaluated for CaCl 2 (aq) and AlCl 3 (aq), i.e., for two solutions with very different cation hydration structures. The effects are significantly larger for the more structured Al 3+ solution. The theoretical Ca 2+ (aq) spectra are compared with new experimental EXAFS data.