Ricerc@Sapienza

A synergic approach combining molecular dynamics (MD) simulations and X-ray absorption spectroscopy has been used to investigate diluted solutions of zinc bis(trifluoromethanesulfonyl)imide (Zn(Tf2N)2) in Tf2N- based ionic liquids (ILs) having different organic cations, namely the 1-butyl-3-methylimidazolium ([C4(mim)]+), 1,8-bis(3-methylimidazolium-1-yl)octane ([C8(mim)2]2+), N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium ([Choline]+) and butyltrimethylammonium ([BTMA]+) ions.

The structural and dynamic properties of the Ba2+ cation in water have been studied by combining quantum mechanical (QM) calculations, molecular dynamics (MD) simulations, and extended X-ray absorption fine structure (EXAFS) spectroscopy. An effective Ba2+-water interaction potential, to be used in the MD simulation of a Ba2+ aqueous solution, has been developed by means of QM methods, and the validity of the whole procedure has been assessed by comparing the theoretical structural results with the EXAFS experimental data.

The structural modifications induced on a 0.5 M Zn2+ aqueous solution by increasing the pressure to 6.4 GPa were investigated using a combination of X-ray absorption near edge structure (XANES) spectroscopy and molecular dynamics (MD) simulations. The Zn K-edge XANES experimental spectra show two different trends depending on the pressure and temperature conditions of the system. On the one hand, when the pressure is increased to 1.0 GPa while keeping the temperature at 300 K, the highly structured nature of Zn2+ second hydration shell is preserved.

In this contribution, we show how it is possible to develop polarizable and non-polarizable force fields to study hydration properties of a whole chemical series based on atomic properties such as ionic radii. In particular, we have addressed the actinide(III) ion series, from U 3+ to Cf 3+ , for which X-ray absorption data and effective ionic radii are available. A polarizable force field has been re-parameterized improving the original one [M. Duvail et al., J. Chem. Phys. 135, 044503 (2011)] which was based on solid state ionic radii.