Dynamic surface boundary conditions

Abstract

A simple model for the treatment of boundaries in molecular dynamics simulations is presented. The method involves the positioning of boundary atoms on a surface that surrounds a system of interest. The boundary atoms interact with the inner region and represent the effect of atoms outside the surface on the dynamics of the atoms inside the surface. The boundary atoms can move but are position restrained. A simple application to liquid argon in a sphere is demonstrated. The methodologies are illustrated for calculating the radial distribution function, density, pressure, potential energy per atom and chemical potential. Also the velocity autocorrelation function and the diffusion constant are calculated. To derive the parameters of the model an empirical approach was followed which consisted of comparing the simulation results of the boundary model with simulation results using periodic boundary conditions. The conclusion is that the present method is able to reproduce the dynamical, structural and thermodynamical properties of a Lennard-Jones liquid. The applicability to systems with long-ranged forces is discussed.