Molecular dynamics computer simulations of solvation dynamics at liquid/liquid interfaces

The solvent dynamic response to electronic transitions at several liquid/liquid interfaces is studied using molecular dynamics computer simulations. The interfaces examined are between water and one of four different organic liquids. The electronic transitions involve a change in the permanent dipole of a dipolar solute located at the interface. Two locations of the solute relative to the interface are studied and are compared with the same process in each of the bulk liquids. The different organic liquids are 1-octanol, 1,2-dichloroethane, n-nonane, and carbon tetrachloride. They are selected to give a range of polarity and of interface structure. The solvent dynamic response at the interface is much more complex than in the bulk. The total relaxation involves multiple time scales corresponding to contributions from both solvents and from the unique structural and dynamic properties of the interface. In particular, interfacial water relaxation may contain a slow component not present in the bulk nor at the water liquid/vapor interface. (C) 2001 American Institute of Physics.