The structures and dynamic properties of anionic surfactant sodium dodecyl sulfate (SDS) at the vapor/liquid interface were investigated using molecular dynamics method. Two systems in which the areas were 0.45 nm² and 0.68 nm² per molecule respectively were selected. The thickness of monolayer was calculated using radial distribution function (RDF), and the order of hydorcarbon chain at the interface for different systems were estimated through number density profiles and orientation correlation for the unit vector in different molecules. Using the diffusion coefficient calculated by mean square displacement (MSD) of water in the systems, it was found that the diffusion of water molecules in the interface was weaker than those in the bulky solution.

Key words: molecular dynamics simulation, monolayer, vapor/liquid interface