Polarization effects in molecular dynamics simulations of glass-formers Ca(NO3)2⋅nH2O, n=4, 6, and 8

Abstract

Thermodynamics, equilibrium structure, and dynamics of glass-forming liquids Ca(NO(3))(2) x nH(2)O, n=4, 6, and 8, have been investigated by molecular dynamics (MD) simulations. A polarizable model was considered for H(2)O and NO(3)(-) on the basis of previous fluctuating charge models for pure water and the molten salt 2Ca(NO(3))(2) x 3 KNO(3). Similar thermodynamic properties have been obtained with nonpolarizable and polarizable models. The glass transition temperature, T(g), estimated from MD simulations was dependent on polarization, in particular the dependence of T(g) with electrolyte concentration. Significant polarization effects on equilibrium structure were observed in cation-cation, cation-anion, and water-water structures. Polarization increases the diffusion coefficient of H(2)O, but does not change significantly the diffusion coefficients of ions. Viscosity decreases upon inclusion of polarization, but the conductivity calculated with the polarizable model is smaller than the nonpolarizable model because polarization enhances anion-cation interactions.