Transfer of a pollutant molecule through a water film supported by MgO(100): Free energy profiles

We have determined the free energy profiles for some pollutant molecules (H Cl, HOCl and CO2) entering and crossing a water film supported on a MgO sub strate. This was done by using atomistic simulation with models for the pol lutant-water, water-water, water-substrate and pollutant-substrate intermol ecular potentials. Our aim is to establish these profiles in order to provi de a foundation for the understanding of the kinetic processes of pollution on a water-covered surface. We show that the water-substrate interface giv es rise to two mimima in the free energy profiles and influence strongly th e transfer process.