5,084 research outputs found
Liquid-Vapor Transition and Critical Behavior of The Ultrasoft Restricted Primitive Model of Polyelectrolytes : a Monte Carlo Study
We present a Monte-Carlo study of the liquid-vapor transition and the
critical behavior of a model of polyelectrolytes with soft gaussian charge
distributions introduced recently by Coslovich, Hansen, and Kahl [J. Chem.
Phys. \textbf{134}, 244514 (2011)]. A finite size study involving four
different volumes in the grand canonical ensemble yields a precise
determination of the critical temperature, chemical potential, and density of
the model. Attempts to determine the nature of the criticality and to obtain
reliable values for the critical exponents are not conclusive.Comment: 14 pages, 4 figure
Monte Carlo simulations of the screening potential of the Yukawa one-component plasma
A Monte Carlo scheme to sample the screening potential H(r) of Yukawa plasmas
notably at short distances is presented. This scheme is based on an importance
sampling technique. Comparisons with former results for the Coulombic
one-component plasma are given. Our Monte Carlo simulations yield an accurate
estimate of H(r) as well for short range and long range interparticle
distances.Comment: to be published in Journal of Physics A: Mathematical and Genera
An accurate equation of state for the one component plasma in the low coupling regime
An accurate equation of state of the one component plasma is obtained in the
low coupling regime . The accuracy results from a smooth
combination of the well-known hypernetted chain integral equation, Monte Carlo
simulations and asymptotic analytical expressions of the excess internal energy
. In particular, special attention has been brought to describe and take
advantage of finite size effects on Monte Carlo results to get the
thermodynamic limit of . This combined approach reproduces very accurately
the different plasma correlation regimes encountered in this range of values of
. This paper extends to low 's an earlier Monte Carlo
simulation study devoted to strongly coupled systems for ({J.-M. Caillol}, {J. Chem. Phys.} \textbf{111}, 6538 (1999)). Analytical
fits of in the range are provided with a
precision that we claim to be not smaller than . HNC equation and
exact asymptotic expressions are shown to give reliable results for
only in narrow intervals, i.e. and respectively
Transport Coefficients of the Yukawa One Component Plasma
We present equilibrium molecular-dynamics computations of the thermal
conductivity and the two viscosities of the Yukawa one-component plasma. The
simulations were performed within periodic boundary conditions and Ewald sums
were implemented for the potentials, the forces, and for all the currents which
enter the Kubo formulas. For large values of the screening parameter, our
estimates of the shear viscosity and the thermal conductivity are in good
agreement with the predictions of the Chapman-Enskog theory.Comment: 11 pages, 2 figure
Description beyond the mean field approximation of an electrolyte confined between two planar metallic electrodes
We study an electrolyte confined in a slab of width composed of two
grounded metallic parallel electrodes. We develop a description of this system
in a low coupling regime beyond the mean field (Poisson--Boltzmann)
approximation. There are two ways to model the metallic boundaries: as ideal
conductors in which the electric potential is zero and it does not fluctuate,
or as good conductors in which the average electric potential is zero but the
thermal fluctuations of the potential are not zero. This latter model is more
realistic. For the ideal conductor model we find that the disjoining pressure
is positive behaves as for large separations with a prefactor that is
universal, i.e. independent of the microscopic constitution of the system. For
the good conductor boundaries the disjoining pressure is negative and it has an
exponential decay for large . We also compute the density and electric
potential profiles inside the electrolyte. These are the same in both models.
If the electrolyte is charge asymmetric we find that the system is not locally
neutral and that a non-zero potential difference builds up between any
electrode and the interior of the system although both electrodes are grounded.Comment: 16 pages, 5 figures, added a new appendix B and a discussion on ideal
conductors vs. good conductor
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
Liquid-vapor transition of systems with mean field universality class
We have considered a system where the interaction, v(r) = v_IS(r) + xi^2
v_MF(r), is given as a linear combination of two potentials, each of which
being characterized with a well-defined critical behavior: for v_IS(r) we have
chosen the potential of the restricted primitive model which is known to belong
to the Ising 3D (IS) universality class, while for v_MF(r) we have considered a
long-range interaction in the Kac-limit, displaying mean field (MF) behavior.
We study the performance of two theoretical approaches and of computer
simulations in the critical region for this particular system and give a
detailed comparison between theories and simulation of the critical region and
the location of the critical point. Both, theory and simulation give evidence
that the system belongs to the MF universality class for any positive value of
xi and that it shows only non-classical behavior for xi=0. While in this
limiting case theoretical approaches are known to fail, we find good agreement
for the critical properties between the theoretical approaches and the
simulations for xi^2 larger than 0.05.Comment: 9 pages, 11 figures, 3 table
Monte Carlo simulation method for Laughlin-like states in a disk geometry
We discuss an alternative accurate Monte Carlo method to calculate the
ground-state energy and related quantities for Laughlin states of the
fractional quantum Hall effect in a disk geometry. This alternative approach
allows us to obtain accurate bulk regime (thermodynamic limit) values for
various quantities from Monte Carlo simulations with a small number of
particles (much smaller than that needed with standard Monte Carlo approaches).Comment: 13 pages, 6 figures, 2 table
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