Molecular dynamics simulations of ion clustering and conductivity in NaI/ether solutions. I. Effect of ion charge

Model systems of sodium iodide dissolved in dimethyl ether were studied in order to investigate the structural and dynamic properties of ionic solutions in small and polymeric ethers having low dielectric constants. Full molecular dynamics simulations were performed at ion charges ranging from 0.5 to 0.1 e, and an algorithm designed to assign ions to clusters and calculate all the terms contributing to ionic conductivity was implemented. Quantitative results were obtained for the contributions of various ionic species to the conductivity. These model systems are stable for ion charges at or below 0.3 e, and a maximum in conductivity is observed at 0.3 e. A range of ion cluster sizes is observed in each system, but the current giving rise to ionic conductivity is due primarily to the movement of free ions and the relative movement of ions within loosely bound pairs.