EXAFS Spectra of the Dilute Solutions of Ca2+ and Sr2+ in Water and Methanol

A set of polarizable ion−water intermolecular potential models were developed that accurately describe solvation enthalpies and structural properties of Ca2+ and Sr2+ in aqueous solution. The molecular dynamics (MD) results were coupled to electron scattering simulations in order to generate the Ca2+ and Sr2+ extended X-ray absorption fine structure (EXAFS) spectra. These MD-XAFS spectra were found to be in good agreement with the corresponding experimental measurements including both the ion-oxygen and the ion-hydrogen distances for the first hydration shell. This work demonstrates that the combination of MD-EXAFS, and the corresponding experiment measurement provides a powerful tool in the analysis of the solvation structure of aqueous ionic solutions. The Ca2+−methanol interaction was also developed, and the dilute Ca2+ MD-EXAFS spectrum in liquid methanol was also predicted using the same approach.