Regensburg 2007 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 30: Poster II

DY 30.46: Poster

Thursday, March 29, 2007, 16:00–18:00, Poster D

Mean field theory for relaxation in random dipolar systems — •Hartmut Grille¹, Wolfgang Dieterich², Philipp Maass¹, and Michael Schulz³ — ¹Technische Universität Ilmenau, 98684 Ilmenau, Germany — ²Universität Konstanz, 78457 Konstanz, Germany — ³Universität Ulm, 89069 Ulm, Germany

Disordered materials often exhibit nearly frequency-independent dielectric loss spectra. This unique feature is far from being understood. By kinetic Monte Carlo simulations it has recently been shown that a dipolar system with positional randomness can provide a mechanism for that "nearly constant loss" (NCL) response [1]. With respect to analytical theories, the long-range and tensorial character of dipole-dipole interactions clearly are complicating factors. In this work we propose a mean field theory for a disordered, dilute system of dipoles, capable of dealing with these problems [2]. The magnitude of dipole moments and their positions are frozen. We derive an approximate expression for the dielectric loss spectra and evaluate it numerically. Influences of different forms of positional randomness and of the system size on the dielectric susceptibility are investigated and compared with the simulations.

[1]

For a review, see W. Dieterich, P. Maass, Chem. Phys. 284, 439 (2002).

[2]

M. Schulz, W. Dieterich, P. Maass, Z. Phys. Chem. 218, 1375 (2004).