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  • 1
    Electronic Resource
    Electronic Resource
    Unsymmetrical electrolytes with adhesive interactions (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 3141-3149 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The sticky electrolyte mode for a weak unsymmetrical electrolyte is solved in the mean spherical approximation (MSA) when there are adhesive interactions between oppositely charged ions. The distribution functions at contact and the thermodynamic properties in this approximation are derived; the solutions reduce to those of corresponding symmetrical adhesive electrolyte studied by Rasaiah and Lee [J. Chem. Phys. 83, 6396 (1985)] when the sizes of the ions and the magnitudes of the charges are made the same and to those of adhesive nonelectrolytes when the charges are removed. When the stickiness is turned off the solutions of the primitive model electrolyte in the MSA are recovered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459784
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  • 2
    Electronic Resource
    Electronic Resource
    Erratum: Solvent effects in weak electrolytes. I. Effect of a hard sphere solvent on the sticky electrolyte model with L=σ [J. Chem. Phys. 91, 495 (1989)] (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4636-4636 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458619
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  • 3
    Electronic Resource
    Electronic Resource
    Erratum: Solvent effects in weak electrolytes. II. Dipolar hard sphere solvent and the sticky electrolyte model with L=σ [J. Chem. Phys. 91, 505 (1989)] (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4636-4636 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458620
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  • 4
    Electronic Resource
    Electronic Resource
    Cavity functions and association in models for weak electrolytes and sticky hard spheres (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 7554-7564 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Weak electrolytes and other association reactions are modeled as sticky spheres. An analysis of the density expansion, including the bridge diagrams, of the cavity functions yAB(L) for sticky hard spheres (charged or uncharged spheres binding at a distance L) leads to an approximation which provides the degree of association α as the solution to a simple quadratic equation determined by the association constant K0 and the cavity function y0AB(L) for the reference system in which the chemical bonding between the reacting species has been turned off. Similar relations are assumed to hold when the bonding is directional and specific enough to lead only to the formation of dimers. Applications to the determination of the reference cavity functions for acetic acid and monochloro acetic acid from experimental data of the degree of association are discussed. In a discrete solvent, the approximation scheme for α remains the same, except that the reference cavity function is scaled differently. Solvent medium effects on the association constant are shown to be related to the cavity function of the undissociated dimer in a pure solvent. An exponential approximation for the reference cavity function y0AB(L) is derived when the associating species are of the same size and the bonding is spherically symmetric. Expressions for the changes in the thermodynamic functions due to association are obtained analytically in terms of the degree of association and the reference cavity functions. The magnitude of the degree of association, calculated from the exponential approximation for y0AB(L), and its effect on the thermodynamic properties are different from what was previously observed using the hypernetted chain (HNC) approximation. The thermodynamics of weak 1–1 electrolytes are discussed using the new method and a comparison is made between the new and old methods for 2–2 electrolytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458191
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  • 5
    Electronic Resource
    Electronic Resource
    Solvent effects in weak electrolytes. I. Effect of a hard sphere solvent on the sticky electrolyte model with L=σ (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 495-504 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Ornstein–Zernike (OZ) equations are solved for the sticky electrolyte model (SEM) with a hard sphere solvent using the hypernetted chain (HNC) approximation for the stickiness and the mean spherical (MS) approximation for the electrical interactions. Relations among the coefficients of Baxter's q functions and the equation for the excess internal energy are given in the MS approximation for L≤σ, where σ is the molecular diameter, and L is the distance at which the oppositely charged ions can stick. The analytical results for L=σ in the HNC/MS and PY/MS approximations are presented in detail. When the charges are switched off, the results automatically lead to those of the sticky hard sphere system; when the stickiness is turned off and the discrete solvent is changed to a continuum, the results lead correctly to those of the restricted primitive model (RPM). The thermodynamic properties of the SEM in a hard sphere solvent for L=σ are calculated and compared with the properties in a continuum solvent; special attention is paid to the derivation of the osmotic coefficient in the McMillan–Mayer system for the SEM and for the corresponding uncharged system. By switching off the charge and the stickiness, the osmotic coefficient of an isotopic solute–solvent system is also obtained. The numerical results show that the hard sphere solvent has a strong packing effect on the structural and thermodynamic properties of the electrolyte and the association of the oppositely charged ions is greatly enhanced by the hard sphere solvent. The influence of a discrete solvent on the osmotic coefficient is quite subtle: for the charged system, the solvent tends to raise the osmotic coefficient; for the sticky hard sphere system, the solvent has just the opposite effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457485
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  • 6
    Electronic Resource
    Electronic Resource
    Solvent effects in weak electrolytes. II. Dipolar hard sphere solvent and the sticky electrolyte model with L=σ (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 505-516 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The sticky electrolyte model in a dipolar solvent is studied in this paper. A detailed separation of the Ornstein–Zernike (OZ) equations and their solution in the mean spherical (MS) approximation for binding (or stickiness) at L=σ are given. The results derived earlier by Adelman and Deutch, Blum et al. and by Høye et al. in this approximation are reproduced when the stickiness is switched off. Also when the density of the solvent goes to zero, the results reduce to those of the sticky electrolyte model (SEM) in a continuum solvent. It is found that the PY/MS approximation gives negative solutions for the association parameter λ, while the HNC/MS approximation works in a narrow interval of the sticky potential well depth ε2 between the positive and negative ions. As expected, the ion association increases when sticky potential well becomes deeper, but the dipole moment of the solvent is found to have a strong screening effect on this association. The study of the radial distribution functions of this system shows that the probability of a free ion appearing near a counter ion is greatly decreased when binding occurs between the oppositely charged ions at the contact; the opposite happens for ions of the same sign. The absolute value of the ion solvation energy becomes smaller as the electrolyte concentration increases and when stickiness between oppositely charged ions is introduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457486
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  • 7
    Electronic Resource
    Electronic Resource
    Fluctuation dominated recombination kinetics with traps (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 5768-5774 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Theoretical and computer simulation studies of annihilation reactions with traps on two and in three dimensional lattice systems are reported for the following reactions: (1) Bimolecular trapping/annihilation: A+A→*; A+T→AT; A+AT→T; (2) unimolecular trapping/annihilation: A+A→*; A→AT; A+AT→*. The mean field analysis and combinatorial calculations of the rate constants given previously for a square lattice are generalized to lattices in two and three dimensions. It is found that the kinetics of trapped A's can be described by mean field theory for bimolecular but not for unimolecular trapping reactions. The kinetics of free A's obeys mean field theory at short times, but at longer times and at low trap densities the free A population decays as a stretched exponential at when large density fluctuations dominate the reaction. This stretched exponential behavior of the Donsker–Varadhan from A(t)∼exp(−td/(d+2)), where d is the dimensionality, already found for the reactant decay in A–A annihilation reactions with traps on a square lattice [Rasaiah et al., J. Phys. Chem. 94, 652 (1990)] was tested for universality by studying triangular and hexagonal lattices in two dimensions (2D) and a cubic lattice in three dimensions (3D). The same behavior is also observed when the free particle annihilation is turned off. The effect of a finite staying probability ps on the kinetics of these reactions are also investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459571
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  • 8
    Electronic Resource
    Electronic Resource
    On the role of solvent electronic polarization in charge transfer reactions (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 8398-8413 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The effect of a solvent's electronic polarization on the rate of a charge transfer reaction is studied in both continuum and discrete solvent models. An effective system Hamiltonian that contains the equilibrium solvation from the solvent electronic polarization is obtained, and leads to an effective matrix element Veff coupling the charge transfer states that is smaller than the gas phase value. Both the effective Hamiltonian and Veff are dependent on the solvent's instantaneous nuclear configuration, and liquid state theory is used to carry out the configuration average. The solvent electronic polarization reduces the transition rate for both adiabatic and nonadiabatic reactions. A standard relation between the equilibrium solvation energy of the reactants and the solvent reorganization energy is established that permits evaluation of the effect of a molecular solvent (using a Drude model for the electronic degrees of freedom) on the rate by evaluating a partition function. This permits use of a path integral formulation for the mixed quantum (electronic polarization) classical (slow nuclear configuration) solvent that leads to the information required for the rate constant. In a strong coupling regime, where the coupling between the charge-transfer species would be so large as to preclude reactant and product species, we show that a new mechanism for charge localization arising from the solvating effect of the electronic polarization may occur, and formulate a rate constant expression for this regime. It has the form of a quantum Kramers rate and shows that the solvent provides a friction effect that will reduce the rate relative to the no-friction rate. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468831
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  • 9
    Electronic Resource
    Electronic Resource
    Solvent dynamical effects on bond-breaking electron transfer reactions (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 8109-8124 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The effects of solvent and intramolecular dynamics on the rates of bond-breaking electron transfer (BBET) reactions is investigated. In the model we adopt, suggested by Saveant [J. Am. Chem. Soc. 109, 6788 (1987)], electron transfer and bond breaking are considered to occur as a concerted process. Thermal equilibrium rate constants kie [i=1(2) denoting the forward (reverse) reaction] are derived and exhibit a characteristic Marcus form, with the reorganization energy equal to the sum of contributions from the solvent, intramolecular vibrational and bond-breaking coordinates. The effect of dynamics on the BBET rate constants is studied by using diffusion-reaction equations. We assume that the intramolecular vibrational coordinate is in equilibrium and the solvent and the bond-breaking coordinates can be out of equilibrium. The survival probabilities are derived analytically with the use of a decoupling approximation. The single exponential decay of the survival probabilities leads to nonthermal-equilibrium rate constants ki that interpolate between the thermal equilibrium kie and diffusion controlled kid rate constants (where motion along the nonequilibrium coordinates control the rate) according to k−1i=k−1ie+k−1id. The diffusion controlled rate constants kid depend on the relaxation times along both the bond-breaking and solvent coordinates. For large activation energies, the fast relaxation will dominate the rate, while for small activation energies, the slow relaxation time will dominate the rate. We also discuss the case of the dynamics along the bond-breaking coordinate being characterized by an energy diffusion process. The rate constant is evaluated for high activation barrier reactions and still has the form given above, with a suitably redefined relaxation time for energy diffusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466805
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  • 10
    Electronic Resource
    Electronic Resource
    An imaginary energy method-based formulation of a quantum rate theory (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 4123-4130 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An imaginary energy method is used to derive a rate constant expression that leads to the WKB tunneling rate at low temperature and to the quantum transition state rate at high temperature. For weak coupling, the imaginary energy method also leads to Fermi's Golden Rule formula. The rate expression is analyzed for the model of one-dimensional motion in a metastable potential profile with linear coupling to a bath of harmonic oscillators (Kramers' problem). We recover the results of the Kramers, Grote-Hynes, and Wolynes (KGHW) theory from the rate expression. Our rate expression is given, in part, in terms of partition functions and is suited to a path integral treatment. The path integral evaluation of the rate constant also yields the KGHW formula. We use the same expression to analyze the low-temperature behavior of tunneling in a double-well potential for a system linearly coupled to a bath, to provide a new expression for electron transfer in the case of strong coupling of the electron to its two sites. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468540
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