Molecular dynamics study of a dipolar fluid between charged plates

Recent experiments and computer simulations of thin films have observed the segregation of nonpolar molecules into layers or sheets parallel to the confining walls. We discuss a molecular dynamics study of a thin film of Stockmayer molecules between Lennard-Jones plates and find that, in the absence of an electric field, the dipoles are mainly oriented parallel to the plates in each layer. The component of the dipole autocorrelation function in this plane decays to zero more slowly than the component perpendicular to the walls. The polarization density profile, with an electric field perpendicular to the plates, is also studied, and is found to oscillate from layer to layer, with a magnitude that is in excess of what is predicted by the Debye theory of dielectric saturation by a factor nearly equal to the ratio of the local density to the average bulk density.