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  • 1
    Electronic Resource
    Electronic Resource
    Primitive models of chemical association. I. Theory and simulation for dimerization (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 7939-7952 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The structure and thermodynamic properties of a model of associating particles that dimerize into fused-sphere dumbbells are investigated by MC simulation and by integral-equation theory. The model particles, introduced by Cummings and Stell, associate as a result of shielded attractive shells. The integral equation theories are of two types. The first is an extension of Wertheim's associative Percus–Yevick (APY) equation to the case of the shielded sticky shell model, which is the limiting case of the shielded attractive shell model that can be handled analytically. The second is the extended mean spherical approximation (EMSA) of Zhou and Stell applied to the shielded sticky shell model. In the case of partially associated systems, the EMSA requires as input the equilibrium association constant, which is obtained here using an exact relation between monomer density and a cavity correlation function, together with an equation of state due to Boublik. The structure obtained from the EMSA is in good agreement with the predictions of the MC simulation over a substantial density range that includes liquid-state densities, while the thermodynamic input from Boublik's equation is in excellent agreement with the simulation results for all densities. Predictions of the APY approximation are also in good agreement with the simulation results as long as the density of the system is relatively low or, at high density, when the hard-core volume of a dimer is not substantially less than that of the two free monomers from which it is formed. There is an intermediate density range in which neither integral-equation theory gives correlation functions of high quantitative accuracy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468221
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  • 2
    Electronic Resource
    Electronic Resource
    Multidensity integral equation theory for highly asymmetric electrolyte solutions (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 5770-5780 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Integral equation theory based on a recently developed multidensity formalism [Mol. Phys. 78, 1247 (1993)] is proposed to study highly asymmetric electrolyte (polyelectrolyte) solutions. The system studied consists of large and highly charged polyions and small counterions having one or two elementary charges. The potential energy of interaction between counterions and polyions is separated into two parts, a strongly attractive part responsible for the association and a nonassociative part. Due to the strong asymmetry in size we can treat each counterion as bondable to a limited number of polyions n, while each polyion can bond arbitrary number of counterions. In our cluster expansion appropriate to the problem the diagrams appearing in the activity expansion of the one-point counterion density are classified in terms of the number of associating bonds incident upon the labeled white counterion circle. The corresponding diagrams for the one-point polyion density are classified in the usual way. A generalized version of the Ornstein–Zernike equation, which involves n+1 counterion densities and one polyion density, together with hypernetted-chain-like (HNC) closure conditions are derived. The simplest two-density version of the theory yields very good agreement with new and existing computer simulations for both thermodynamical and structural properties of these systems. This good agreement extends into the region of parameter space where the ordinary HNC approximation does not have a convergent solution. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469308
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  • 3
    Electronic Resource
    Electronic Resource
    Integral equation theory for associating liquids: Weakly associating 2–2 electrolytes (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 9151-9164 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Formation of ion pairs in a 2–2 aqueous electrolyte is studied using a generalization of Wertheim's formalism, designed to treat explicitly association between molecules. The ions in the model electrolyte interact via a continuous potential energy (unlike previous studies), which combines the long-range Coulomb interaction with a soft repulsive potential at short distances. Both the derivation of new equations, including approximately the formation of trimers, and numerical solution of the resultant equations are presented here. The predictions of the theory are in excellent agreement with new molecular dynamics (MD) simulations of the same electrolyte. Explicit predictions are made for the fraction of monomers, dimers, and trimers in the electrolyte, over the full range of concentrations of interest for association, from 0.001 to 0.2 M.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461195
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  • 4
    Electronic Resource
    Electronic Resource
    Thermodynamics of the associative mean spherical approximation for the fluid of dimerizing particles (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 3709-3715 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Analytical expressions for the thermodynamic properties of the n-component mixture of dimerizing hard spheres with a long-range potential are derived within the associative mean spherical approximation. The derivation is based on the extension of the Høye–Stell scheme [J. Chem. Phys. 67, 439 (1977)] in the framework of the Wertheim's two-density formalism for associating fluids and the exponential approximation recently suggested by Bernard and Blum [J. Chem. Phys. 104, 4746 (1996)]. In the complete association limit, in which the two-density associative mean spherical approximation reduces to Chandler–Silbey–Ladanyi mean spherical approximation, results of the present study coincide with the corresponding results obtained earlier by the other authors. Closed form expressions for the Helmholtz free energy, chemical potential, and pressure of the complete association version of the electrolyte restricted primitive model with the additional sticky-point attraction are derived. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475764
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  • 5
    Electronic Resource
    Electronic Resource
    Solution of the associative mean spherical approximation for the shielded sticky point electrolyte model (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 1081-1089 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An analytical solution of the two-density Ornstein–Zernike (OZ) equation with the associative mean spherical approximation (AMSA) closure is obtained for the shielded sticky point (SSP) electrolyte model. The model is presented by the dimerizing version of the restricted primitive electrolyte model with dimerization which occurs due to the site–site sticky interaction at distances less than the ionic hard-core diameter. The present version of the AMSA is an extension of the associative MSA proposed recently [M. Holovko and Yu. Kalyuzhnyi, Mol. Phys. 73, 1145 (1991)]. It is demonstrated that, in the limit of complete association, the present two-density OZ equation reduces to the Chandler–Silbey–Ladanyi equation. Predictions from the AMSA in this limit are compared with those obtained by Monte Carlo simulations. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470763
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  • 6
    Electronic Resource
    Electronic Resource
    Static dielectric properties of a flexible water model (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 2964-2971 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The linear response theory is applied to the interaction site model for the evaluation of static dielectric properties of a flexible water model. The atom–atom radial distribution functions derived from hybridization of the computer simulations and optimized cluster theory [A. D. Trokhymchuk, M. F. Holovko, E. Spohr, and K. Heinzinger, Mol. Phys. 77, 903 (1992)] are employed for the calculation of the polarization structure factor and the moments of the polarization correlation function. The color charge version of the dipolar hard sphere model [F. O. Raineri, H. Resat, and H. L. Friedman, J. Chem. Phys. 96, 3068 (1992)] proved to be helpful for the understanding of the effects of intramolecular charge distribution and flexibility on the dielectric properties of the interaction site model. The dielectric constant for the flexible BJH water model is calculated and the region of negative values of the static dielectric function is obtained. The possibility of a subdivision of this region into two parts at k about 1–2 A(ring)−1 is pointed out.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465202
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  • 7
    Electronic Resource
    Electronic Resource
    Analytic solution of the RISM equation forn s-atomic symmetric molecules (1990)
    Springer
    Czechoslovak journal of physics 40 (1990), S. 1098-1106 
    Details
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A general method of an analytic solution of the RISM equation based on the Baxter factorization is explicitly extended to three- and four-atomic symmetric homonuclear molecules. Results of higher order approximations (beyond the zero pole approximation) are compared with numerical results and it is shown that the analytic solution converges to the numerical one for allL}〈1. The role of poles of the intramolecular structural function 1/W(k) depending on the number of sites, site-site span, and density is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01597970
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  • 8
    Electronic Resource
    Electronic Resource
    Highly Asymmetric Electrolytes in the Associative Mean-Spherical Approximation (2000)
    Springer
    Journal of statistical physics 100 (2000), S. 243-265 
    Details
    ISSN: 1572-9613
    Keywords: highly asymmetric electrolyte ; primitive model ; association ; mean spherical approximation ; osmotic coefficient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The associate mean-spherical approximation (AMSA) is used to derive the closed-form expressions for the thermodynamic properties of an (n+m)-component mixture of sticky charged hard spheres, with m components representing polyions and n components representing counterions. The present version of the AMSA explicitly takes into account association effects due to the high asymmetry in charge and size of the ions, assuming that counterions bind to only one polyion, while the polyions can bind to an arbitrary number of counterions. Within this formalism an extension of the Ebeling–Grigo choice for the association constant is proposed. The derived equations apply to an arbitrary number of components; however, the numerical results for thermodynamic properties presented here are obtained for a system containing one counterion and one macroion (1+1 component) species only. In our calculation the ions are pictured as charged spheres of different sizes (primitive model) embedded in a dielectric continuum. Asymmetries in charge of −10:+1, −10:+2, −20:+1, and −20:+2 and asymmetries in diameter of 2:0.4nm and 3:0.4nm are studied. Monte Carlo simulations are performed for the same model solution. By comparison with new and existing computer simulations it is demonstrated that the present version of the AMSA provides semiquantitative or better predictions for the excess internal energy and osmotic coefficient in the range of parameters where the regular hypernetted chain (HNC) and improved (associative) HNC do not yield convergent solutions. The AMSA liquid–gas phase diagram in the limit of complete association (infinitely strong sticky interaction) is calculated for models with different degrees of asymmetry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018699914319
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  • 9
    Electronic Resource
    Electronic Resource
    The Laplace transform of the MSA pair distribution functions between macroions in an ion-dipole fluid (1993)
    Springer
    Journal of statistical physics 72 (1993), S. 1391-1399 
    Details
    ISSN: 1572-9613
    Keywords: Colloids ; solvation force ; ion-dipole fluid ; mean spherical approximation ; macroions ; electrolyte ; solvent ; correlation functions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Laplace transform is obtained for the pair distribution function between a pair of ions, an ion and a macroion, and a pair of macroions in an ion-dipole fluid. This fluid is a simplified model of an electrolyte with a discrete model of solvent (hard spheres with embedded point dipoles). From these results, an expression for the solvation force between macroions is obtained. This result consists of the classical DLVO result plus a series of corrections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01048192
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  • 10
    Electronic Resource
    Electronic Resource
    A solution of the multiple-binding mean spherical approximation for ionic mixtures (1996)
    Springer
    Journal of statistical physics 84 (1996), S. 191-204 
    Details
    ISSN: 1572-9613
    Keywords: Ionic mixtures ; mean spherical approximation ; polymerizing ions ; multiple binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The mean spherical approximation (MSA) for an arbitrary mixture of charged hard spheres with saturating bonds is solved in the Wertheim formalism. Any number of bonds is allowed. It is shown that the general solution is given in terms of a screening MSA-like parameterΓ T , a cross-interaction parameterη β that will depend on the binding association equations, the set of binding association fractions, and an additional algebraic equation. The equation forΓ T is given for the general case. The equation forη β , however, depends strongly on the particular closure that is used to compute the contact pair correlation function. The full solution requires, as in the dimer case recently solved by Blum and Bernard, solvingm+2 equations and additionally the inversion of a matrix of size [(ν−1)m] for a system withm components and ν bonds. We recall that when ν=1, only dimers are allowed; for ν=2, only linear chains are formed: and when ν≥3, branching of the polymers occurs. It can be shown that the excess entropy for the polymer case is as before,ΔS MSA=(Γ T )3/3π + sticky terms, where the sticky terms depend on the model and will be given in future work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02179582
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