Simulation of effective dielectric permittivities: Comparison of different crystal structures, amorphous systems, and nanocomposites

摘要

We compute the effective dielectric permittivities of systems of induced dipoles on a microscopic scale by calculating the local electric fields. In contrast to macroscopic or medium field calculations the method of local fields considers all dipolar fields within the sample taking account of the electrodes by the method of images. In this way, all depolarizing fields in inhomogeneous samples are regarded. Results for amorphous dielectrics and materials with different crystal structures are compared. Furthermore, nanocomposites are investigated, with regions of different structures and polarizabilities. We found that the conventional Clausius-Mossotti formula approximates very well the numerical results for amorphous samples and samples with cubic lattices in a wide parameter range. Using averaged particle density and averaged polarizability, the Clausius-Mossotti formula yields the effective permittivities even of CsCl structure, including two different species of particles, and of many nanocomposites. Deviations from Clausius-Mossotti we found mainly for tetragonal lattices.