77,465 research outputs found
Low-temperature and high-temperature approximations for penetrable-sphere fluids. Comparison with Monte Carlo simulations and integral equation theories
The two-body interaction in dilute solutions of polymer chains in good
solvents can be modeled by means of effective bounded potentials, the simplest
of which being that of penetrable spheres (PSs). In this paper we construct two
simple analytical theories for the structural properties of PS fluids: a
low-temperature (LT) approximation, that can be seen as an extension to PSs of
the well-known solution of the Percus-Yevick (PY) equation for hard spheres,
and a high-temperature (HT) approximation based on the exact asymptotic
behavior in the limit of infinite temperature. Monte Carlo simulations for a
wide range of temperatures and densities are performed to assess the validity
of both theories. It is found that, despite their simplicity, the HT and LT
approximations exhibit a fair agreement with the simulation data within their
respective domains of applicability, so that they complement each other. A
comparison with numerical solutions of the PY and the hypernetted-chain
approximations is also carried out, the latter showing a very good performance,
except inside the core at low temperatures.Comment: 14 pages, 8 figures; v2: some figures redone; small change
Properties of the reaction front in a reaction-subdiffusion process
We study the reaction front for the process in which the reagents
move subdiffusively. We propose a fractional reaction-subdiffusion equation in
which both the motion and the reaction terms are affected by the subdiffusive
character of the process. Scaling solutions to these equations are presented
and compared with those of a direct numerical integration of the equations. We
find that for reactants whose mean square displacement varies sublinearly with
time as , the scaling behaviors of the reaction front can
be recovered from those of the corresponding diffusive problem with the
substitution Comment: Errata corrected, one reference update
Test of a universality ansatz for the contact values of the radial distribution functions of hard-sphere mixtures near a hard wall
Recent Monte Carlo simulation results for the contact values of polydisperse
hard-sphere mixtures at a hard planar wall are considered in the light of a
universality assumption made in approximate theoretical approaches. It is found
that the data seem to fulfill the universality ansatz reasonably well, thus
opening up the possibility of inferring properties of complicated systems from
the study of simpler onesComment: 9 pages, 2 figures; v2: minor changes; to be published in the special
issue of Molecular Physics dedicated to the Seventh Liblice Conference on the
Statistical Mechanics of Liquids (Lednice, Czech Republic, June 11-16, 2006
Communication: Inferring the equation of state of a metastable hard-sphere fluid from the equation of state of a hard-sphere mixture at high densities
A possible approximate route to obtain the equation of state of the
monodisperse hard-sphere system in the metastable fluid region from the
knowledge of the equation of state of a hard-sphere mixture at high densities
is discussed. The proposal is illustrated by using recent Monte Carlo
simulation data for the pressure of a binary mixture. It is further shown to
exhibit high internal consistency.Comment: 4 pages, 2 figures; v2: Simulation data for one-component hard
spheres included in Fig.
Fourth virial coefficients of asymmetric nonadditive hard-disc mixtures
The fourth virial coefficient of asymmetric nonadditive binary mixtures of
hard disks is computed with a standard Monte Carlo method. Wide ranges of size
ratio () and nonadditivity () are
covered. A comparison is made between the numerical results and those that
follow from some theoretical developments. The possible use of these data in
the derivation of new equations of state for these mixtures is illustrated by
considering a rescaled virial expansion truncated to fourth order. The
numerical results obtained using this equation of state are compared with Monte
Carlo simulation data in the case of a size ratio and two
nonadditivities .Comment: 9 pages, 7 figures; v2: section on equation of state added; tables
moved to supplementary material
(http://jcp.aip.org/resource/1/jcpsa6/v136/i18/p184505_s1#artObjSF
- …