On the hydration structure of LiCl aqueous solutions: A Reverse Monte Carlo based combination of diffraction data and Molecular Dynamics simulations

Reverse Monte Carlo (RMC) calculations have been carried out on aqueous LiCl solutions at several concentrations, comparing experimental X-ray and neutron diffraction data with partial radial distribution functions (prdf) from Molecular Dynamics (MD) simulations based on conventional ion-ion, ion-water, and water-water pair potentials. The RMC calculations indicate that the hydration shell of the Li+ ions could be even more structured than computer simulations predict, containing at high concentrations unusually few water molecules, of the order of 2 to 3. Concerning the consistency between the structures based on potential models and diffraction data: the ion-water partial radial distribution functions (prdf) from MD are found to be consistent with the experimental data whereas the water-water and ion-ion partials are more problematic. The most serious deficiency is that at high salt concentrations the O-O prdf cannot be made consistent with the present X-ray diffraction data.