Molecular dynamics simulation of the energy distributions of molecules in liquid solutions

Abstract

Abstract A solution is modelled as a classical 2D molecular system consisting of two types of molecules having different interaction parameters. The interaction is modelled by Lennard - Jones - type potentials. Molecular Dynamics simulations of solutions of soft molecules imbedded into a bath of rather hard solvent molecules are performed. From the molecular dynamics trajectories we derive the energy distributions and study local energy excitations of the solute and the solvent molecules. In particular the dynamics of activation processes (high energy events) is investigated for a special model: We simulate the thermal equilibrium of one molecule with Lennard-Jones 8-6-interactions imbedded into a bath of molecules with 18-6 interactions. It is shown that in thermal equilibrium a region of temperatures and densities exists, where the mean one-particle energy has a relative maximum. In this region the potential part of the thermal energy is preferably partitioned to the solvent molecules. Further we show that the energy distribution of the soft molecules shows longer tails than that of the hard molecules. On the basis of these distributions it is concluded that energy spots at the solute molecules may appear which possibly could lead to the enhancement of solute reactions.