Dinâmica Molecular Grande Canônica de Fluidos Complexos

Abstract

In this work, extensive Molecular Dynamic simulations in the Grand Canonical ensemble (GCMD) have been performed to study the equilibrium and non-equilibrium properties of solutions containing a simple electrolyte. First, we introduce the GCMD method for a Lennard-Jones (LJ) fluid, discussing the effect of using thermostats on the equilibrium and dynamical properties of LJ species, such as diffusivity. We compare different scenarios when we use the concept of local and global control of the chemical potential for different concentrations. We have shown that the Fick’s law of diffusion is obtained only when the GCMD method is combined with different thermostats, such as Andersen and Langevin Dynamics. After that, we have extended the GCMD method for electrolyte solutions. We compare the equilibrium properties obtained from GCMD method with the results derived from Monte Carlo simulations in the Grand Canonical ensemble (GCMC). We discuss in a systematic way the conditions of having the same results when using both methods. Finally, we analyze the diffusion of ionic species between two local control volumes for different chemical potential gradients. Once again, we show that the Fick’s law is obtained only when we use termostats in the simulations.