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  • 1
    Electronic Resource
    Electronic Resource
    Analytical approach to molecular liquids. I. Site–site interaction model using an extended mean-spherical approximation (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4861-4868 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The observation that the intramolecular direct-correlation-function matrix is very closely approximated by its large-r form for rigid diatomics suggests an approximation such that the site–site Ornstein–Zernike equation becomes analytically solvable for several molecular models of interest. Alternatively, approximation of the particle–particle direct correlation function by its asymptotic form directly yields the same approximation, in particle–particle (in contrast to site–site) language. Applications of this approximation, which can be regarded as an extended mean spherical approximation when viewed in particle–particle terms, are made to rigid hard diatomics, dipolar diatomics, and a tetrahedral molecular model. The close but subtle connections between our approximation procedure and earlier approximations are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456724
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  • 2
    Electronic Resource
    Electronic Resource
    Analytical approach to molecular liquids. II. Solvation of ions in molecular fluids (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4869-4878 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Analytical equations are obtained for the pair correlation functions in the mean spherical approximation (MSA) for two charged hard-sphere ions in a model molecular solvent. Model solvents of dipolar dumbbells (which may be partially dissociative) or charged hard-spheres fused in a tetrahedral configuration are treated in an extended MSA. The resulting expressions for the Born solvation free energy of an ion are very similar to that obtained earlier by Chan et al. for a charged hard-sphere ion in a dipolar hard-sphere solvent. The solvent averaged ion–ion potentials are obtained in the hypernetted chain approximation. Comparisons among results of various solvents are also made. In order of increasing oscillation amplitudes of the solvent averaged ion–ion potential for given molecular density and dipole moment we have continuum (very-much-less-than)dumbbell≤tetrahedral〈dipolar hard sphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456725
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  • 3
    Electronic Resource
    Electronic Resource
    Analytical approach to molecular liquids. IV. Solvation dynamics and electron-transfer reactions (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4885-4890 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The solvation dynamics of a pair of ions rigidly held a fixed distance from each other in either a dipolar hard-sphere solvent or a dipolar dumbbell solvent is investigated under the mean spherical approximation (MSA) applied to an interaction-site model in which the pair of ions is treated as a rigid extended dipolar dumbbell. An analytical expression for the reorganization free energy for a charge transfer reaction is obtained and compared with numerical results obtained via a thermodynamic cycle. Solvent effects on the rate of a charge transfer reaction are also investigated using the dielectric Green-function theory developed by Newton and Friedman.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456727
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  • 4
    Electronic Resource
    Electronic Resource
    Analytical approach to molecular liquids. III. The Born solvation free energy of two fixed ions in a dipolar solvent (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4879-4884 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Born solvation free energy (BSFE) of two ions at a fixed distance from one another in a model polar solvent is obtained via two approaches. In the interaction-site approach, the two ions are modeled as a rigid extended dipolar dumbbell. Analytical expressions for the BSFE for such a dumbbell model in a dipolar dumbbell and a dipolar hard-sphere solvent are obtained under a mean spherical approximation (MSA). In the second approach, a thermodynamic cycle is established such that the BSFE for two ions a fixed distance apart can be expressed in terms of the solvent-averaged potential between the two ions and other known quantities. The results obtained via these two approaches are reasonably consistent, with the thermodynamic-cycle BSFE as a function of distance exhibiting more of the structure one expects to find in a molecular solvent. Both BSFE functions are substantially different from the corresponding continuum-solvent result. When the distance between two ions goes to infinity, our results reduce to earlier results for the single-ion BSFE obtained by us for a dipolar dumbbell solvent and by Chan et al. for a dipolar hard-sphere solvent. The BSFE of two ions in an ionic solution with a dielectric-continuum solvent is also obtained; it is found that the contribution of other ionic particles to the total BSFE is usually negligible if the dielectric constant of the solution is assumed to be unchanged.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456726
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  • 5
    Electronic Resource
    Electronic Resource
    The theory of semipermeable vesicles and membranes: An integral-equation approach. III. Vesicles with internal nonpermeating ions (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3208-3211 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The system of a fluid in the presence of a spherical semipermeable vesicle (SPV) with the freely mobile nonpermeating species inside the vesicle is investigated via an integral-equation approach. This system can be used to model certain feature of a biological cell, permeable to simple ions, in which solute proteins inside the cell are unable to permeate its walls. As an illustrative example of the use of our integral equations, the analytical solution for density profiles in the mean-spherical approximation/Debye–Hückel approximation (MSA/DH) is obtained, where the MSA is used to obtain the density profiles near a membrane and the DH approximation to obtain the bulk pair correlation functions. A method which applies to nonmobile protein fixed inside a cell is also considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456941
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  • 6
    Electronic Resource
    Electronic Resource
    Note on standard free energy of transfer and partitioning of ionic species between two fluid phases (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 3836-3839 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigate the partition of ionic species in a system of two phases that are immiscible even in the limit of vanishing ionic concentrations. An analytic expression for the solvation free energy and for the standard free energy of transfer is obtained for dipolar hard-sphere solvents in the mean spherical approximation. We find that both dipolar hard-sphere solvents and continuum solvent models yield an electric potential difference (equilibrium junction potential) between two pure solvents in contact that is identically zero. Simple analytic expressions for partition coefficients and junction potentials are obtained in the ideal-solution limit for these solvent models. We note that for the junction potential the ideal solution limits differ in general from the pure-solvent values. For nonideal solutions, approximations based on the mean spherical approximation can be applied conveniently to calculate the activities of ionic species and to obtain the partition coefficients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455704
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  • 7
    Electronic Resource
    Electronic Resource
    The theory of semipermeable vesicles and membranes: An integral-equation approach. II. Donnan equilibrium (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 7020-7029 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Integral equations that yield the charge and density profiles are derived for a Donnan system, in which an ionic solution is separated into two regions by a semipermeable membrane (SPM) or a spherical semipermeable vesicle (SPV). These equations are obtained from the Ornstein–Zernike (OZ) equation. We show how quantitative results can be obtained from either the mean spherical approximation (MSA) closure or the hypernetted-chain (HNC) closure for profiles. Use is made of bulk-correlation input obtained by means of the Debye–Hückel approximation, the MSA approximation, or the HNC approximation. The resulting approximations will be referred as MSA/DH, HNC/DH, MSA/MSA, etc. The system on which we focus contains three charged hard-sphere species: cation, anion, and a large ion (a protein or polymer ion) separated by a plane SPM, through which the large ion cannot pass, and to one side of which all large ions are confined, or a spherical SPV, outside of which the large ions are confined. Analytical expressions for the bulk density ratio between the two sides of a plane membrane as well as the membrane potential in various approximations are obtained. Results obtained from these expresssions are compared with the results obtained by equating electrochemical potentials. A new contact-value theorem is provided for the plane SPM system. Analytical solutions for the charge profile and the potential profile in the MSA/DH approximation are obtained. It turns out that results obtained in the HNC/DH approximation are exactly the same as those obtained by using 1D nonlinear Poisson–Boltzmann equations if the repulsive cores of the macroions are neglected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455328
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  • 8
    Electronic Resource
    Electronic Resource
    Nonlocal integral-equation approximations. II. Lennard-Jones fluids (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 5544-5550 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The zeroth order (hydrostatic) nonlocal integral-equation approximation is applied here to Lennard-Jones (LJ) fluids. Systems of homogeneous LJ fluids are investigated, as well as LJ fluids near a hard wall, a model CO2 wall, and inside two model CO2 walls. The hydrostatic hypernetted chain (HHNC) approximation is shown to be better than both the Percus–Yevick and the hypernetted chain approximations when compared with computer simulations. The phenomena of solid wetting by liquid, solid wetting by gas, and capillary condensation are predicted by the HHNC approximation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458487
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  • 9
    Electronic Resource
    Electronic Resource
    Nonlocal integral-equation approximations. I. The zeroth order (hydrostatic) approximation with applications (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 5533-5543 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A formally exact nonlocal density-functional expansion procedure for direct correlation functions developed earlier by Stell for a homogeneous system, and extended by Blum and Stell, Sullivan and Stell, and ourselves to various inhomogeneous systems, is used here to derive nonlocal integral-equation approximations. Two of the simplest of these approximations (zeroth order), which we shall characterize here as the hydrostatic Percus–Yevick (HPY) approximation and the hydrostatic hypernetted-chain (HHNC) approximation, respectively, are shown to be capable of accounting for wetting transitions on the basis of general theoretical considerations. Before turning to such transitions, we investigate in this first paper of a series the case of homogeneous hard-sphere fluids and hard spheres near a hard wall as well as the case of hard spheres inside a slit pore. Numerical results show that the HHNC approximation is better than the HNC approximation for both the homogeneous and inhomogeneous systems considered here while the HPY approximation appears to overcorrect the PY approximation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458486
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  • 10
    Electronic Resource
    Electronic Resource
    Chemical association in simple models of molecular and ionic fluids (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3618-3623 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A simple approximation scheme is given for the association constant of a family of models of associating particles introduced and considered by Cummings and Stell, Rasaiah et al., and Stell. The result correctly reduces to the law of mass action at low concentrations. For the ionic-species version, the theory requires accurate assessment of the cavity function of charged hard spheres, for which we develop a recipe. We show the close similarity (and some differences) between the above models and those considered by Wertheim, through a simple extensions of his models. We also note the equivalence of our approximation and Wertheim's first-order thermodynamic perturbation theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456894
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