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

Abstract

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.