HIGHLY CONCENTRATED SALT-SOLUTIONS - MOLECULAR-DYNAMICS SIMULATIONS OF STRUCTURE AND TRANSPORT

Molecular dynamics (MD) simulations in NaI solutions, where the solven t has been represented by the Stockmayer fluid, were performed as a fu nction of temperature, salt concentration, and solvent dipole strength . At higher temperatures contact ion pairs become more prevalent, rega rdless of solvent strength. An examination of the temperature dependen ce of the potential of mean force demonstrates the entropic nature of this effect. The transport properties calculated in the simulations ar e dependent on the balance between solvent dielectric constant and ion charge. In systems with a large solvent dipole moment, the ions appea r to be independently mobile, and deviations from Nernst-Einstein beha vior are small. In systems of smaller solvent dipole moment or greater ion charge, the ions form clusters, and large deviations from Nernst- Einstein behavior are observed.