Douglas J. Henderson

Integral equation theory for Lennard‐Jones fluids: The bridge function and applications to pure fluids and mixtures

The pure Lennard‐Jones fluid and various binary mixtures of Lennard‐Jones fluids are studied by both molecular dynamics simulation and with a new integral equation which is based on that proposed by Duh and Haymet recently [J. Chem. Phys. 103, 2625 (1995)]. The structural and thermodynamic properties calculated from this integral equation show excellent agreement with simulations for both pure fluids and mixtures under the conditions which we have studied. For mixtures, the effect of deviations from the Lorentz‐Berthelot (LB) mixing rules for the interaction parameters between unlike species is studied. Positive deviations from the nonadditivity of the molecular cores leads to an entropy driven tendency for the species to separate. This tendency persists even in the presence of a deviation from the LB rule for the energy parameter which enhances the attraction of the unlike species. On the other hand, in the case of negative deviations from nonadditivity, the tendency for association may be either energy ...

Inverse temperature expansion of some parameters arising from the solution of the mean spherical approximation integral equation for a Yukawa fluid

Analytic formulas, within the mean spherical approximation, are given through fifth order for the inverse temperature expansion of the energy and the pair correlation function at contact for a fluid whose molecules interact via a Yukawa potential with a hard core. This series converges rapidly if the Yukawa potential has a long range. Reliable results are obtained from this series even when the potential has a short range.

Ionic Soft Matter: Modern Trends in Theory and Applications

Dedication.- Preface.- Field theoretical approach for ionic systems D. di Caprio, J. Stafiej.- Induced charge computation method D. Boda et al.- Concept of ion association in the theory of electrolyte solutions M. Holovko.- Towards the role of the range of intermolecular interactions I. Nezbeda , J. Kolafa.- Collective dynamics in ionic fluids I. Mryglod et al.- Criticality of ionic liquids in solution W. Schroer.- Liquid/vapor criticality in Coulombic and related fluids P.J. Camp et al.- Macroions in solution V. Vlachy et al.- Anomalous small-angle X-ray scattering in rod-like polyelectrolytes M. Ballauff.- Macroions under confinement A.D. Trokhymchuk.- Grain interaction and ordering in a dusty plasmas O. Bystrenko.- Dipolar fluid inclusions in charged matrices M.J. Fernaud, E. Lomba .- Solute ions at ice/water interface A.D.J. Haymet et al.- Proton transport in polymer electrolyte fuel cell membranes E. Spohr.- DNA saline solutions near surfaces B.M. Pettit.- Charge transport in highly-radioactive substance O. Zhydkov.- Participants.- Index.-

DENSITY PROFILES OF A MODEL OF ASSOCIATING HARD SPHERES IN CONTACT WITH A CRYSTALLINE SURFACE : AN INTEGRAL EQUATION APPROACH

Density profiles of a fluid of associating or chemically reacting hard spheres near a crystalline surface are studied. The model of Cummings and Stell is utilized to provide the description of a bulk associating fluid. The crystal symmetry of the substrate surface plane is assumed to be that of the (100) plane of the face centered cubic lattice. The model of the particle–solid interaction is that proposed by Steele. The effect of association of the particles of the bulk fluid on the density profiles of particles near the crystalline surface is investigated within the hypernetted chain approximation. When the first layer is completed, some dimers tend to be vertically oriented over the adsorption site.

Integral equation study of additive two-component mixtures of hard spheres

The Ornstein-Zernike equation for additive hard sphere mixtures is solved numerically by using the Martynov-Sarkisov (MS) closure and a recent modification of the Verlet (MV) closure. A comparison of the predictions for the equation of state and, to a lesser extent, the contact values of the radial distribution function, shows both theories to give similar, reasonably accurate, results in most situations. However, an examination of the pair cavity functions for zero separation shows the two closures to give quite different results, and the MV closure results are believed to be better. More attention should be given to the cavity function at zero separation. In addition, the MV closure satisfies known asymptotic relations for a small concentration of exceedingly large spheres, whereas the MS and Percus-Yevick closures do not satisfy these relations.

Parametrization of the radial distribution function of a Yukawa fluid

Abstract We give semi-empirical expressions for five terms in an inverse temperature expansion of the radial distribution function of a Yukawa fluid. The parameters in these terms are chosen to fit what we believe should be an accurate equation of state when either the energy or pressure routes is used. Thus, a measure of self consistency is achieved. The equation of state which is the basis of our fit is the inverse temperature expansion of the Yukawa fluid free energy, obtained from the mean spherical approximation but modified to give reasonable results at low densities.

Adsorption of fluids on colloidal particles: a density functional approach

Density functional results are presented for adsorption of simple fluids on colloidal particles. Two models of colloidal particles are considered: first a study of adsorption on a large hard sphere, and second the application of the theory to describe adsorption on a large particle interacting via Lennard-Jones type attractive-repulsive forces. In both cases the theoretical predictions are compared with Monte Carlo data. It was found that the accuracy of the theory becomes better when the size of the colloidal particle increases. A study is also reported of wetting and its dependence on the size of the colloidal particles. As expected, the wetting temperature increases with decreasing colloidal particle size.

Adsorption of chemically reacting fluids on a crystalline surface

In this note we propose a model for the description of density profiles of a chemically reacting fluid in contact with a crystalline surface. The model is solved in the Percus-Yevick approximation of the singlet theory for inhomogeneous fluids. We find the density profiles to be affected appreciably by the chemical interactions.

DENSITY PROFILES OF ASSOCIATING FLUID NEAR A HARD WALL : PY/EMSA AND HNC/EMSA SINGLET THEORY

A two-component model of hard spheres with a spherically symmetric associative interaction between the particles of different species near a hard wall is studied by suing the integral equation method. It is shown that the extended mean spherical approximation for the bulk associating fluid in conjunction with the Percus-Yevick closure of the singlet level theory of inhomogeneous fluid leads to very good agreement of theoretical density profiles with simulation data for highly associated fluid at a high bulk density.

Density profiles of chemically reacting fluids in slit-like pores

A model of a chemically reacting fluid in a slit-like pore is studied. The density profiles of the fluid particles inside the pore, the adsorption isotherms, and the solvation force acting between the walls of the pore are investigated within the integral equation method. The Percus-Yevick and hypernetted chain approximations for the fluid particle-pore correlations are used. The model for the bulk chemically reacting fluid is that proposed by Cummings and Stell for a mixture of overlapping hard spheres. The investigations are performed for pores of different width, at different densities of the bulk fluid which is in an equilibrium with the confined fluid and for different degrees of bulk fluid association. The bulk fluid is described by using the Percus-Yevick approximation. A wide range of thermodynamic states and different bonding lengths between the reactants are investigated. It is shown that the effect of a chemical reaction in the bulk fluid produces qualitative changes in the behaviour of the den...