J.Phys.Chem. v.100, p.16410 (1996)

Concentration Effects in Aqueous NaCl Solutions. A Molecular Dynamics Simulation.

Alexander P. Lyubartsev and Aatto Laaksonen

Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, S-109 61, Stockholm, Sweden

Abstract

A series of constant-temperature/constant-pressure molecular dynamics simulations of aqueous NaCl solution at different salt concentrations is carried out to investigate the structure and the dynamical properties. The simulations were performed with the number of molecules ranging from 256 to 2000. The simulations cover several nanoseconds to ensure the convergence of the results and enabling a proper determination of ion-ion radial distribution functions. The flexible SPC water model is used as the solvent, while the ions are treated as charged Lennard-Jones particles. Only a weak influence of the salt concentration is found on the ion-ion pair correlation functions. The structures of the hydrated shells around ion pairs are studied using three-body correlation functions. The self-diffusion and interdiffusion coefficients are found decreasing with an increase of salt concentration. Molar conductivities are calculated at different salt concentrations. Residence times of water molecules in the hydration shells as well as residence times of contact and solvent-separated ion configurations are determined.

Paper (PostScript file)

Supporting information:

Hydration shells of ions

MDynaMix files:

Water: H2O.mmol
Na+ ion: Na+_SD.mmol
Cl- ion: Cl-_SD.mmol