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  • 1
    Electronic Resource
    Electronic Resource
    Study of polar dumbbell fluids from the gaseous to the liquid densities by the reference interaction site model-1 and -2 integral equations (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 10084-10091 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The structures and the thermodynamic properties of a fluid composed of a nonpolar or a polar dumbbell molecule have been studied from the gaslike to the liquidlike density regions based on two types of the reference interaction site model (RISM) integral equation theories (RISM-1 and RISM-2). This is the first application of the RISM-2 theory to a polar dumbbell fluid. We have proven that the RISM-2 theory with the hypernetted-chain (HNC) approximation has an inconsistency with respect to the zeroth-order relation between site–site total correlation functions and site–site direct correlation functions in the Fourier space. An hypothetical bridge function is introduced to remedy this inconsistency, which works well to give good information on the structure and the dielectric constant in the lower-density region. On the other hand, the RISM-1 theory works well in the higher-density region, but not well in the lower-density region. Complemental application of these theories, that is, the RISM-1 theory for the high-density region and the RISM-2 theory for the low-density region, allows us to understand the properties of fluid over wide density regions. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472837
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  • 2
    Electronic Resource
    Electronic Resource
    Density dependence of solvation properties in polar dumbbell fluids from gaseous to liquid densities (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 4662-4675 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The solvent density dependence of the solvation energy difference associated with a charge transfer process in a polar dumbbell fluid is studied from the gaslike to the liquidlike densities by means of two types of the integral equation theories and the Monte Carlo simulation. The polar dumbbell fluid model including the Coulombic interaction explicitly has succeeded in a qualitative reproduction of quite a larger density dependence of the solvation energy in the low-density region than that in the higher-density region. The origin of the density dependence has been attributed to the difference in the reaction field response at various densities. At the low density, the reaction field shows a highly enhanced nonlinear response to the solute dipole moment. The nonlinear enhancement is an intrinsic nature in the gaseous dielectric solvation, and is due to the enhanced local density around the solute molecule with increasing the solute charge. On the other hand, the reaction field at the high density responds almost linearly to the solute dipole moment. The analysis based on the integral equation has clarified that the high linearity at the liquid density is closely related to the invariance of the radial distribution between cores in spite of the charging on the solute, which reflects the highly packed structure at the high density. When the solute dipole moment is quite large, we observe the dielectric saturation at the high density, where the enhanced local density around the solute does not result in the increase of the reaction field because of the saturation in the orientational correlation between the solute and solvent dipoles. Even when the solute dipole moment is small enough not to cause the nonlinear response, the reaction field is induced nonlinearly to the solvent density, which is interpreted not only by the local density but also by the contribution per solvent molecule at various densities. This study demonstrates that the following two properties often neglected so far have significant effect on the evaluation of the solvation energy difference at various densities: one is the nonlinearly enhanced field response at the gaseous density, and the other is the density variation of the reaction field induced per solvent molecule. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481022
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of the solvent density and species on the back-electron transfer rate in the hexamethylbenzene/tetracyanoethylene charge-transfer complex (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 1485-1498 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The back-electron transfer (b-ET) process in the hexamethylbenzene/tetracyanoethylene charge-transfer complex was studied by the transient absorption spectroscopy in several fluids (ethane, nitrous oxide, carbon dioxide, and trifluoromethane) from the critical density to twice that of it at 323.2 K. The b-ET rate was determined by the decay rate of the excited state absorption. The b-ET rate increased with the increase of solvent density in carbon dioxide and nitrous oxide. The b-ET rate also increased in the order of ethane, nitrous oxide, carbon dioxide, and trifluoromethane, compared at the similar reduced density divided by the solvent critical density. Based on the formulation by Marcus and Jortner, the reaction free energy and the solvent reorganization energy were estimated from the change of the absorption spectrum relative to the gaseous phase spectrum, simply by assuming that the intramolecular reorganization energy does not depend on the solvent density and the species. The reaction free energy and the solvent reorganization energy in fluids obtained in this way were almost linearly correlated, and the density dependence was larger in the lower density region. The b-ET rates in various conditions showed a good correlation with the reaction free energy estimated from the spectral simulation. The b-ET rate showed a significant isotope effect by perdeuteriation of hexamethylbenzene as is predicted by the fluorescence quantum yield [K. Kulinowski et al., J. Phys. Chem. 99, 17715 (1995)], which could not be reproduced by this model. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475520
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