Dynamic and Static Properties of Aqueous NaCl Solutions at 25°C as a Function of NaCl Concentration: A Molecular Dynamics Simulation Study

Abstract

We present the result of molecular dynamics (MD) simulations to calculate the molar conductivity Λm= Na++ Cl- of NaCl in SPC/E water at 25°C as a function of NaCl concentration (c) using Ewald sums employing a velocity Verlet algorithm. It is found that the MD result for Λm with Ewald sum parameter = 0.10 Å-1 gives the closest one to the experimental data and that the obtained radial distribution functions gii(r) with = 0.10 Å-1 show a dramatic change with a very deep minimum of gNaCl(r) and, as a result, sharp maxima of gNaNa(r) and gClCl(r) at the distance 9.95 Å, which indicates a characteristic of ionic atmosphere, the basis of the Debye-Hückel theory of ionic solutions. The static and dynamic properties of NaCl (aq) solutions are analyzed in terms of radial distribution functions, hydration numbers, coordination numbers around Na+ and Cl-, residence times of water around Na+ and Cl-, water diffusion, and ion-ion electrostatic energies to explain the behavior of the molar conductivity Λm of NaCl obtained from our MD simulations.