Simulation of heterogeneous nanodielectrics using the local field method

The dipole-dipole interaction is significantly responsible for the dielectric behaviour of matter. In the past, several analytic models have been developed to describe these dielectric properties. With increasing performance of personal computers, bigger and bigger systems can be simulated numerically on a microscopic scale by calculating the local electric fields at each dipole site. In doing so and applying the method of image dipoles in order to consider the electrodes we can easily calculate the local fields, polarization and effective susceptibility for a system of nanometric size with dimensions smaller than 100 Å which consists of more than one sort of atoms, e. g. binary mixtures, or different lattice constants. With this method all depolarization fields within the sample are regarded inherently. The different phases can be arranged differently so that we can investigate the influence of the granularity of the mixture. Defects and inclusions can also be easily included. We have studied for example the impact of an air-filled sphere in a dielectric on the effective susceptibility and simulated local fields for a pyramidal inclusion. For a given plane in the three-dimensional sample we can determine the local fields at (grain) boundaries.