2,103 research outputs found
A self-consistent renormalized Jellium approach for calculating structural and thermodynamic properties of charge stabilized colloidal suspensions
An approach is proposed which allows to self-consistently calculate the
structural and thermodynamic properties of highly charged aqueous colloidal
suspensions. The method is based on the renormalized Jellium model with the
background charge distribution related to the colloid-colloid correlation
function. The theory is used to calculate the correlation functions and the
effective colloidal charges for suspension containing additional monovalent
electrolyte. The predictions of the theory are in excellent agreement with the
Monte Carlo simulations
Equilibrium properties of charged microgels: a Poisson-Boltzmann-Flory approach
The equilibrium properties of ionic microgels are investigated using a
combination of the Poisson-Boltzmann and Flory theories. Swelling behavior,
density profiles, and effective charges are all calculated in a self-consistent
way. Special attention is given to the effects of salinity on these quantities.
It is found that the equilibrium microgel size is strongly influenced by the
amount of added salt. Increasing the salt concentration leads to a considerable
reduction of the microgel volume, which therefore releases its internal
material -- solvent molecules and dissociated ions -- into the solution.
Finally, the question of charge renormalization of ionic microgels in the
context of the cell model is briefly addressed
Lattice Model of an Ionic Liquid at an Electrified Interface
We study ionic liquids interacting with electrified interfaces. The ionic
fluid is modeled as a Coulomb lattice gas. We compare the ionic density
profiles calculated using a popular modified Poisson-Boltzmann equation with
the explicit Monte Carlo simulations. The modified Poisson-Boltzmann theory
fails to capture the structural features of the double layer and is also unable
to correctly predict the ionic density at the electrified interface. The
lattice Monte Carlo simulations qualitatively capture the coarse-grained
structure of the double layer in the continuum. We propose a convolution
relation that semiquantitatively relates the ionic density profiles of a
continuum ionic liquid and its lattice counterpart near an electrified
interface
Yukawa particles in a confining potential
We study the density distribution of repulsive Yukawa particles confined by
an external potential. In the weak coupling limit, we show that the mean-field
theory is able to accurately account for the particle distribution. In the
strong coupling limit, the correlations between the particles become important
and the mean-field theory fails. For strongly correlated systems, we construct
a density functional theory which provides an excellent description of the
particle distribution, without any adjustable parameters.Comment: Submitte
Does the thermal spike affect low-energy ion-induced interfacial mixing?
Molecular dynamics simulations have been used to obtain the three-dimensional
distribution of interfacial mixing and cascade defects in Ti/Pt multilayer
system due to single 1 keV impacts at grazing angle of incidence. The
Ti/Pt system was chosen because of its relatively high heat of mixing in the
binary alloy and therefore a suitable candidate for testing the effect of heat
of mixing on ion-beam mixing. However, the calculated mixing profile is not
sensitive to the heat of mixing. Therefore the thermal spike model of mixing is
not fully supported under these irradiation conditions. Instead we found that
the majority of mixing occurs after the thermal spike during the relaxation
process. These conclusions are supported by liquid, vacancy as well as adatom
analysis. The interfacial mixing is in various aspects anomalous in this
system: the time evolution of mixing is leading to a phase delay for Ti mixing,
and Pt exhibits an unexpected double peaked mixing evolution. The reasons to
these effects are discussed.Comment: 7 pages, 12 figures, Nucl. Instr. Meth. B211, 524. (2003
Equation of state of charged colloidal suspensions and its dependence on the thermodynamic route
The thermodynamic properties of highly charged colloidal suspensions in
contact with a salt reservoir are investigated in the framework of the
Renormalized Jellium Model (RJM). It is found that the equation of state is
very sensitive to the particular thermodynamic route used to obtain it.
Specifically, the osmotic pressure calculated within the RJM using the contact
value theorem can be very different from the pressure calculated using the
Kirkwood-Buff fluctuation relations. On the other hand, Monte Carlo (MC)
simulations show that both the effective pair potentials and the correlation
functions are accurately predicted by the RJM. It is suggested that the lack of
self-consistency in the thermodynamics of the RJM is a result of neglected
electrostatic correlations between the counterions and coions
Reply to Comment on "Quantum dense key distribution"
In this Reply we propose a modified security proof of the Quantum Dense Key
Distribution protocol detecting also the eavesdropping attack proposed by
Wojcik in his Comment.Comment: To appear on PRA with minor change
Thermodynamic and dynamic anomalies for a three dimensional isotropic core-softened potential
Using molecular dynamics simulations and integral equations (Rogers-Young,
Percus-Yevick and hypernetted chain closures) we investigate the thermodynamic
of particles interacting with continuous core-softened intermolecular
potential. Dynamic properties are also analyzed by the simulations. We show
that, for a chosen shape of the potential, the density, at constant pressure,
has a maximum for a certain temperature. The line of temperatures of maximum
density (TMD) was determined in the pressure-temperature phase diagram.
Similarly the diffusion constant at a constant temperature, , has a maximum
at a density and a minimum at a density .
In the pressure-temperature phase-diagram the line of extrema in diffusivity is
outside of TMD line. Although in this interparticle potential lacks
directionality, this is the same behavior observed in SPC/E water.Comment: 16 page
Nontrivial dependence of dielectric stiffness and SHG on dc bias in relaxors and dipole glasses
Dielectric permittivity and Second Harmonic Generation (SHG) studies in the
field-cooled mode show a linear dependence of dielectric stiffness (inverse
dielectric permittivity) on dc bias in PMN-PT crystals and SHG intensity in
KTaO:Li at small Li concentrations. We explain this unusual result in the
framework of a theory of transverse, hydrodynamic-type, instability of local
polarization.Comment: 5 figure
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