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Anisotropic diffusion of tagged spheres near the isotropic-nematic phase transition

Vasanthi, R and Ravichandran, S and Bagchi, Biman (2001) Anisotropic diffusion of tagged spheres near the isotropic-nematic phase transition. In: Journal of Chemical Physics, 115 (21). pp. 10022-10028.


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Molecular dynamics simulations of diffusion of isolated tagged spheres in liquid crystalline molecules have been carried out. While the diffusion is isotropic at density slightly below the isotropic-nematic phase transition, it is found to become strongly anisotropic very close to the I-N transition where the diffusion perpendicular to the direction of the order parameter g(D \perp) decouples from the parallel (D\parallel) component. The diffusion coefficient of the sphere also shows a marked slowing down as the I-N transition approaches, in accordance with the mode coupling theory analysis. The variation of the orientational order parameter with the density shows a sharp transition at a reduced density, \rho*IN where plot of the ratio, D\parallel /D\perp against the reduced density,\rho * clearly shows the emergence of anisotropy. D\perp could be fitted to a form (\rho*c - \rho*)p which is slightly larger than \rho*IN. The diffusion shows a strong non-Stokesian dependence on the radius of the spheres, in agreement with recent experiments.

Item Type: Journal Article
Publication: Journal of Chemical Physics
Publisher: American Institute of Physics
Additional Information: Copyright for this article belongs to American Institute of Physics (AIP).
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited: 30 Dec 2004
Last Modified: 19 Sep 2010 04:17
URI: http://eprints.iisc.ac.in/id/eprint/2541

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