Can models of charged rods show features of undercooled liquids?

Abstract

We have performed molecular dynamic simulations of linear charged particle models. They are defined by rods with discrete charges at the ends. Intermolecular interactions are described by a coulombic term plus a Kihara potential for the rest of interactions. Our simulations were carried out for low and high charged systems either at thermodynamic states corresponding to the liquid branch of vapor–liquid equilibrium curve of non-charged rods or at supercritical temperatures of the non-charged systems. Our results show that rods with null or small discrete charge behave as normal liquids: the viscosity increases with rod length and they present short range velocity self-correlation function (VSCF). However, for medium and large discrete charges VSCF shows a very long range tail and the apparent viscosity increases by several orders of magnitude with a non-Arrhenius dependence with temperature. In some cases a transition from Arrhenius to non-Arrhenius behavior for medium charges is observed. Our results strongly suggest that systems behave as normal liquids when the rods have null or small charges and show undercooled liquid behavior for larger discrete charges at low temperatures.