Ewald methods in molecular dynamics for systems of finite extent in one of three dimensions

We describe a new method for the treatment of molecular-dynamics computer simulation for systems with long-range interactions when the system to be simulated is only infinite in two of the dimensions of the three-dimensional space. Such problems arise, for example, in the study of surfaces. We report a method to deal with these problems based on Ewald techniques but involving several new features. Numerical tests show that our methods are fast and accurate enough to be feasible for study of the systems of interest, though not quite as fast as the corresponding techniques for bulk systems. We report results of a simulation of water between two dielectric walls using the new methods.