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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/2942

Title: DIFFUSION IN RANDOM MEDIA
Authors: SOLOMON, NEGASH ASFAW
Advisors: Dr. TATEK YERGOU
Keywords: physics
Copyright: Jun-2010
Date Added: 10-May-2012
Publisher: AAU
Abstract: In this work we present Monte Carlo simulations of particle and polymer diffusion in two dimensional (2D) media with obstacles distributed randomly. For diffusion of a particle, the mean-square displacement of the diffusing species is proportional to time for normal diffusion. But in disordered systems anomalous diffusion may occur, in which the mean- square displacement is proportional to some other power of time. In the presence of moderate concentration of obstacles, diffusion is anomalous for short times and normal for long times. Monte Carlo calculations are used to characterize anomalous diffusion for obstacle concentrations between zero and the percolation threshold. As the obstacle concentration approaches the percolation threshold, diffusion becomes more anomalous for long times; the anomalous diffusion exponent increases. In polymer diffusion, we present a new effective algorithm to simulate dynamic properties of polymeric systems confined to lattice. The algorithm displays Rouse behavior for all spatial dimensions. The systems are simulated by bond fluctuation method to study both the static and dynamic properties of the polymer chains. For static properties we calculated the average mean- 2 square end-to-end distance R2 (N ) and the mean-square radius of gyration Rg (N ) . Both the end-to-end distance and the radius of gyration are proportional to some power 2 of the number of monomers (N), R2 (N ) ∝ N 3/2 and Rg (N ) ∝ N 3/2 . For dynamical properties we look at the mean-square displacement of the total chain. For short times the mean-square displacement of the monomers g1 (t) and the mean-square displacement of the monomers relative to the chains center of mass g2 (t) show the same behavior and for long times the mean-square displacement of the center of mass g3 (t) takes over.
URI: http://hdl.handle.net/123456789/2942
Appears in:Thesis - Physics

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