616 research outputs found
On the contact conditions for the charge profile in the theory of the electrical double layer for nonsymmetrical electrolytes
The contact value of the charge profile for nonsymmetrical electrolytes is
presented as the sum of three contributions. One of them is the normal
component of the Maxwell electrostatic stress tensor. The second one is the
surface electrostatic property defined as the integral of the product of the
gradient of the electrical potential and the density distribution function of
coions. The third term is the bulk contribution defined by the sum for anions
and for cations of the product of their charge and their partial pressure. For
noncharged surfaces only the last two are present and have the same sign in the
case of size asymmetry. In the case of charge asymmetry the contact value of
the charge profile is the result of the competitions of bulk and surface terms
in which the bulk term is dominant. Using both the contact theorems for the
density and the charge profiles, the exact expressions for the contact values
of the profiles of coions and counterions are obtained and some related
properties are discussed.Comment: 5 page
Spontaneous polarisation of the neutral interface for valence asymmetric coulombic systems
In this paper, we discuss the phenomenon of a spontaneous polarisation of a
neutral hard planar interface for valence asymmetric coulombic systems. Within
a field theoretical description, we account for the existence of non trivial
charge density and electric potential profiles. The analysis of the phenomenon
shows that the effect is related to combinatorics in relation with the
existence of the two independent species cations and anions. This simple and
basic feature is related to the quantum mechanical properties of the system.
The theoretical results are compared with numerical simulations data and are
shown to be in very good agreement, which a fortiori justifies our physical
interpretation.Comment: 12 pages, 11 figure
Equilibrium properties of the lattice system with SALR interaction potential on a square lattice: quasi-chemical approximation versus Monte Carlo simulation
The lattice system with competing interactions that models biological objects
(colloids, ensembles of protein molecules, etc.) is considered. This system is
the lattice fluid on a square lattice with attractive interaction between
nearest neighbours and repulsive interaction between next-next-nearest
neighbours. The geometric order parameter is introduced for describing the
ordered phases in this system. The critical value of the order parameter is
estimated and the phase diagram of the system is constructed. The simple
quasi-chemical approximation (QChA) is proposed for the system under
consideration. The data of Monte Carlo simulation of equilibrium properties of
the model are compared with the results of QChA. It is shown that QChA provides
reasonable semiquantitative results for the systems studied and can be used as
the basis for next order approximations.Comment: 10 pages, 8 figure
The effect of short-range interaction and correlations on the charge and electric field distribution in a model solid electrolyte
A simple lattice model of a solid electrolyte presented as a xy-slab geometry
system of mobile cations on a background of energetic landscape of the host
system and a compensating field of uniformly distributed anions is studied. The
system is confined in the z-direction between two oppositely charged walls,
which are in parallel to xy-plane. Besides the long-range Coulomb interactions
appearing in the system, the short-range attractive potential between cations
is considered in our study. We propose the mean field description of this model
and extend it by taking into account correlation effects at short distances.
Using the free energy minimization at each of z-coordinates, the corresponding
set of non-linear equations for the chemical potential is derived. The set of
equations was solved numerically with respect to the charge density
distribution in order to calculate the cations distribution profile and the
electrostatic potential in the system along z-direction under different
conditions. An asymmetry of charge distribution profile with respect to the
midplane of the system is observed. The effects of the short-range interactions
and pair correlations on the charge and electric field distributions are
demonstrated
New mean field theories for the liquid-vapor transition of charged hard spheres
The phase behavior of the primitive model of electrolytes is studied in the
framework of various mean field approximations obtained recently by means of
methods pertaining to statistical field theory (CAILLOL, J.-M., 2004,
\textit{J. Stat. Phys.}, \textbf{115}, 1461). The role of the regularization of
the Coulomb potential at short distances is discussed in details and the link
with more traditional approximations of the theory of liquids is discussed. The
values computed for the critical temperatures, chemical potentials, and
densities are compared with available Monte Carlo data and other theoretical
predictions.Comment: 17 pages, 4 figures, 3 table
Nematic fluid at a hard wall in the mean field approximation
In the framework of a field theoretical approach we study Maier-Saupe
nematogenic fluid in contact with a hard wall. The pair interaction potential
of the considered model consists of an isotropic and an anisotropic Yukawa
terms. In the mean field approximation the contact theorem is proved. For the
case of the nematic director being oriented perpendicular to the wall,
analytical expressions for the density and order parameter profiles are
obtained. It is shown that in a certain thermodynamic region the nematic fluid
near the interface can be more diluted and less orientationally ordered than in
the bulk region.Comment: 6 pages, 1 figur
A formally exact field theory for classical systems at equilibrium
We propose a formally exact statistical field theory for describing classical
fluids with ingredients similar to those introduced in quantum field theory. We
consider the following essential and related problems : i) how to find the
correct field functional (Hamiltonian) which determines the partition function,
ii) how to introduce in a field theory the equivalent of the indiscernibility
of particles, iii) how to test the validity of this approach. We can use a
simple Hamiltonian in which a local functional transposes, in terms of fields,
the equivalent of the indiscernibility of particles. The diagrammatic expansion
and the renormalization of this term is presented. This corresponds to a non
standard problem in Feynman expansion and requires a careful investigation.
Then a non-local term associated with an interaction pair potential is
introduced in the Hamiltonian. It has been shown that there exists a mapping
between this approach and the standard statistical mechanics given in terms of
Mayer function expansion. We show on three properties (the chemical potential,
the so-called contact theorem and the interfacial properties) that in the field
theory the correlations are shifted on non usual quantities. Some perspectives
of the theory are given.Comment: 20 pages, 8 figure
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