A comparison of classical interatomic potentials applied to highly concentrated aqueous lithium chloride solutions

Abstract

Aqueous lithium chloride solutions up to very high concentrations were investigated in classical molecular dynamics simulations. Various force fields based on the 12-6 Lennard-Jones model, parametrized for non-polarizable water solvent molecules (SPC/E, TIP4P, TIP4PEw), were inspected. Twenty-nine combinations of ion-water interaction models were examined at four different salt concentrations. Densities, static dielectric constants and self-diffusion coefficients were calculated. Results derived from the different force fields scatter over a wide range of values. Neutron and X-ray weighted structure factors were also calculated from the radial distribution functions and compared with experimental data. It was found that the agreement between calculated and experimental curves is rather poor for several investigated potential models, even though some of them have previously been applied in computer simulations. None of the investigated models yield satisfactory results for all the tested quantities. Only two parameter sets provide acceptable predictions for the structure of highly concentrated aqueous LiCl solutions. Some approaches for adjusting potential parameters, such as those of Aragones [Aragones et al., J. Phys. Chem. B 118 (2014) 7680] and Pluharova [Pluharova et al, J. Phys. Chem. A 117 (2013) 11766], were tested as well; the simulations presented here underline their usefulness. These refining methods are suited to obtain more appropriate ion/water potentials.