Molecular dynamics simulations of restricted primitive model 1:1 electrolytes

Abstract A new molecular dynamics method is described which enables the simultaneous simulation of hard sphere collisions in the presence of “soft” forces. Calculations show that the Debye-Huckel theory, DHX, describes well the equation of state of charged hard spheres up to an equivalent electrolyte concentration of 1 M. This results from a cancellation of errors, rather than the validity of the underlying assumptions. Better agreement for higher concentrations up to 2 M is obtained with previous Monte Carlo simulatons and higher order theories such as MSA and HNC. A two-, three- and four-particle resolution of the specific heat reveals that the four-particle term is mainly responsible for the poor statistics of this quantity. Below 3 M self-diffusion is well described by Enskog's theory. However, there is an approximately 15% deviation from the Nernst-Einstein equation.