COMPUTER-SIMULATION OF AQUEOUS NA-CL ELECTROLYTES

The equilibrium structure of aqueous Na-Cl electrolytes in the concent ration regime between 1 and 5 mol l-1 is studied by means of a molecul ar dynamics computer simulation using interaction-site descriptions of water and the ionic components. The electrostatic interactions are tr eated both with the newly developed charged-clouds scheme and with Ewa ld summation. In the case of a 5 mol l-1 electrolyte, the results for pair correlations obtained by the two methods are in excellent agreeme nt. However, the charged-clouds technique is much faster than Ewald su mmation and makes simulations at lower salt concentrations feasible. I t is found that both ion-water and ion-ion correlation functions depen d only weakly on the ionic concentration. Sodium and chloride ions exh ibit only a negligible tendency to form contact pairs. In particular, no chloride ion pairs in contact are observed.