Structure and size distribution of percolating clusters. Comparison with gelling systems |
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Authors: | JC Gimel T Nicolai D Durand JM Teuler |
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Institution: | (1) Laboratoire de Physique de la Matière Condensée, Faculté des Sciences Ben M'sik, Casablanca, BP 7955, Morocco, MA |
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Abstract: | Dynamic properties of Brownian particles immersed in a periodic potential with two barriers V1 and V2 (symmetric bistable potential) are studied by using the Fokker-Planck equation which we solve numerically by the matrix continued
fraction method. This study will therefore serve to demonstrate the influence of this form of potential, which is of great
interest for superionic conductors and for many other solid systems, on the diffusion process. Thus, we have calculated the
full width at half maximum (FWHM) ) of the quasi-elastic line of the dynamic structure factor, for a large range of values of the wave-vectors q. Our results show clearly that, by varying the ratio of the barriers strictly between and 1, the Fokker-Planck equation describes a diffusive process which has some characteristic of jump and
liquid-like regimes. While in the limit cases, i.e. when tends to or 1, the diffusion process can be described only by a simple jump motion. However, the jump-lengths corresponding
to each limit case are not equal. In general the change of the ratio is found to have a significant effect on the character
of the diffusive motion. We have also performed Fokker-Planck dynamics calculations of the diffusion coefficient in a bistable
potential. We have found a good agreement between numerical calculations and analytical approximation results obtained in
the high friction limit.
Received 25 May 1998 and Received in final form 15 November 1998 |
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Keywords: | PACS 05 40 -a Fluctuation phenomena random processes noise and Brownian motion - 82 20 Fd Stochastic and trajectory models other theories and models - 05 60 -k Transport processes |
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