Dresden 2009 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 16: Thin Films and Nanostructures III

DF 16.3: Vortrag

Donnerstag, 26. März 2009, 15:30–15:50, WIL B321

The Local Field Method for Dielectric Nanocomposites — •Markus Kühn and Herbert Kliem — Saarland University, Germany

We focus on nanodielectrics consisting of two different phases. The systems are embedded between coplanar conducting electrodes which are taken into account by the method of image dipoles. Binary mixtures are modelled by neutral atoms with polarizabilities α and β, respectively. The different atoms are statistically arranged on cubic lattice sites. For different volume ratios and different dielectric contrasts of the two phases the dipole moments and local fields are calculated. For vanishing α- or rather β-phase the corresponding Lorentz fields are obtained, respectively. The simulation results are compared to the common Maxwell-Garnett mixing rule. In contrast to the local field method which also inherently takes into account all depolarization effects, macroscopic mixing rules are based on a homogenization of heterogeneous systems. This simplified description of the dielectric neglects the real microstructure and the varying local fields. In addition, we investigated two-dimensional nanodielectrics where we have a polar inclusion modelled by permanent bidirectional dipoles at cubic lattice sites. The shape of the inclusion is random and it is surrounded by a matrix of induced dipoles placed at cubic lattice sites. Again, the local field method yields the locally varying dipole moments due to the microstructure.