The Dielectric Properties of Simulated Water Droplets

Simulation of a droplet system has been suggested as a way to study local molecular processes in aqueous solution. To be valid, such a simulation should reproduce the results of simulations on an infinite solution. While it has been shown that the structural and thermodynamical features in the central part of a pure water droplet are very much like those of bulk water, no study has been done on the dielectric properties of a water droplet. Here, we report the estimation of the dielectric constants of SPC water droplets. We find that the dielectric constant of a droplet as a whole is very low. However, the dielectric constant of the central part of the water droplet can be as high as 50. Apparently, the molecules in the surface layer preferentially assume orientations so as to compensate the instantaneous dipole moment of the core volume. The influence of the surface layer extends over circa 6 Å.