Molecular dynamics simulation of the activation of soft molecules solved in condensed media

By means of molecular dynamics simulations we study local energy excitations of soft molecules solved in liquids or solids. The basic configuration studied is a soft impurity imbedded into a dense system of hard molecules. In the first part we reformulate an earlier result for the 1D-case, which demonstrates that soliton excitations and soliton fusion at the soft sites may lead to local energy spots at the soft molecules. In the following part the dynamics of activation processes (high energy events) due to nonlinear collision mechanisms in 1D-, 2D- and 3D-systems is studied by means of MD-simulations. We simulate the thermal equilibrium of one soft molecule with r−2-repulsion imbedded into a bath of molecules with r−8-repulsion. It is shown that in thermal equilibrium a region of temperatures exists, where the mean potential energy of the soft molecules is several times higher than that of the hard molecules of the solvent. Further we show that the potential energy distribution of the soft molecules shows a longer energy tail.