Regensburg 2013 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 35: Brownian Motion and Transport

DY 35.4: Vortrag

Freitag, 15. März 2013, 10:15–10:30, H48

Determination of eigenvalues of the diffusion tensor in anisotropic systems with orientation change in time and space — •Mario Heidernätsch and Günter Radons — Chemnitz University of Technology, D-09126 Chemnitz, Germany

Anisotropic diffusion is one possible generalization of homogeneous diffusion processes. It occurs typically in systems with anisotropic media such as liquid crystals or in isotropic media when the diffusing particle or molecule has an ellipsoidal shape. It can be formally described by an extended Fokker-Planck-equation using a diffusion tensor. We show how the moments of the distribution of diffusivities [1] can be used in a simple fashion to obtain the eigenvalues of the diffusion tensor from trajectories of such anisotropic processes. For the example of a three-dimensional anisotropic systems with twist, we show how the method regains the principal diffusion coefficients. In such systems, which are mathematical equivalent to two-dimensional diffusion of an ellipsoid in isotropic media, other methods are harder to accomplish and need better data [2], or might even fail.

[1] M. Bauer et al., J. Chem. Phys. 135, 144118 (2011)

[2] C. Ribrault et al., Phys. Rev. E 75, 021112 (2007)