Bagchi, Biman (2001) Relation between orientational correlation time and the selfdiffusion coefficient of tagged probes in viscous liquids: a density functional theory analysis Journal of Chemical Physics, 115 (5). pp. 22072211. ISSN 00219606

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Official URL: http://jcp.aip.org/jcpsa6/v115/i5/p2207_s1
Related URL: http://dx.doi.org/10.1063/1.1385558
Abstract
The usual explanation for the observed inverse relation between the orientational correlation time (τ_{R}); the selfdiffusion (D_{S}) of a tagged solute probe in a viscous liquid is in terms of the hydrodynamic relations which are known to have dubious conceptual validity for small molecules. Here; we present a microscopic derivation of the relation between τ_{R}; D_{S}. This derivation is based on the general ideas of the mode coupling theory; but uses the timedependent density functional theory to obtain the torquetorque; forceforce time correlation functions on the solute probe. Our analysis shows that the orientational correlation time (τ_{R}) is inversely proportional to the translational diffusion coefficient (D_{0}) of the solvent molecules. Thus; the viscosity dependence of orientational correlation time enters through the viscosity dependence of the translational diffusion (D_{0}). The same theoretical analysis also shows that the translational diffusion coefficient of the solute probe (D_{S}) is also proportional to the translational diffusion coefficient; D_{0}; of the solvent molecules. This result is in agreement with the recent computer simulation results which show that the product of τ_{R}; D_{S} is a weak function of the density (hence of the viscosity) of the liquid. The microscopic expressions provide explanation; in terms of the solutesolvent direct correlation functions; the reason for the sensitivity of orientational diffusion to solutesolvent interaction potential.
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ID Code:  4211 
Deposited On:  18 Oct 2010 09:10 
Last Modified:  16 May 2016 14:53 
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