Anomalous orientational relaxation of solute probes in binary mixtures

Bhattacharyya, Sarika ; Bagchi, Biman (2001) Anomalous orientational relaxation of solute probes in binary mixtures Journal of Chemical Physics, 115 (19). pp. 9065-9071. ISSN 0021-9606

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The orientation of a solute probe in a binary mixture often exhibits multiple relaxation times at the same solvent viscosity but different compositions [Beddard et al., Nature (London) 294, 145 (1981)]. In order to understand this interesting observation, we have carried out (NPT) molecular dynamics simulation study of rotation of prolate ellipsoids in binary mixtures. The simulations show that for a broad range of model parameters the experimental behavior can be reproduced. The plot of orientational relaxation time versus the solvent viscosity, the latter changed by varying the composition, shows a nonmonotonic viscosity dependence. The nature of the plot is found to depend on the system parameters, especially on the solute-solvent interactions. A mode coupling theoretical analysis of this complex dependence of the rotational relaxation time τR on the binary viscosity η is presented. The theory can qualitatively explain the origin of the multiple relaxation time at the same viscosity.

Item Type:Article
Source:Copyright of this article belongs to American Institute of Physics.
ID Code:4194
Deposited On:18 Oct 2010 09:13
Last Modified:16 May 2016 14:52

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