Dynamical properties of electrolyte solutions from Brownian dynamics simulations

We study the dynamics of charged particles in aqueous solutions in the fram ework of the continuous solvent model by smart Brownian dynamics simulation s. Transport coefficients of simple electrolyte solutions (KCl between 0.1 and 2 mol/L) are computed from the simulations and compared to experimental data. The simulation method is then applied to more complex systems: aqueo us cryptate solutions. in the latter case, we compare the experimental valu es for the conductivity to the simulation results. Both direct and indirect hydrodynamic interactions are taken into account in the simulations: the f irst ones are modelled by a solvent-averaged pairwise interaction potential and the second ones are evaluated by using the Rotne-Prager approximation. The smart Brownian dynamics method allows to use long time steps of about 0.1 ps and to generate trajectories of several ns in total. It is shown tha t hydrodynamic interactions are crucial to compute transport coefficients i n agreement with experimental data. The self-diffusion coefficients are sli ghtly enhanced and the conductivity is lowered when hydrodynamic interactio ns are taken into account.