Local order in aqueous lithium chloride solutions as studied by X-ray scattering and molecular dynamics simulations

X-ray scattering and molecular dynamics (MD) simulations are carried out on pure water and aqueous lithium chloride solutions at four salt concentrations 0.5, 1.5, 3 and 4 molal. Both experimental and theoretical results indicate a decrease of hydrogen bonding in liquid water as compared with pure fluid. MD results also show that the hydration number around the cation decreases with increasing salt concentration; simultaneously the fraction of contact ion pairs increases and that of solvent-separated ion pairs decreases. The local order in the systems, as deduced from MD simulation by considering the rigid SPC water model and the Lennard-Jones potential, is directly confronted with that extracted from X-ray data. A good agreement is shown between the theoretical and experimental pair correlation functions of each system. (c) 2006 Elsevier B.V. All rights reserved.