3,650 research outputs found
The effect of the lateral interactions on the critical behavior of long straight rigid rods on two-dimensional lattices
Using Monte Carlo simulations and finite-size scaling analysis, the critical
behavior of attractive rigid rods of length k (k-mers) on square lattices at
intermediate density has been studied. A nematic phase, characterized by a big
domain of parallel k-mers, was found. This ordered phase is separated from the
isotropic state by a continuous transition occurring at a intermediate density
\theta_c, which increases linearly with the magnitude of the lateral
interactions.Comment: 7 pages, 6 figure
Entropy-driven phase transition in a system of long rods on a square lattice
The isotropic-nematic (I-N) phase transition in a system of long straight
rigid rods of length k on square lattices is studied by combining Monte Carlo
simulations and theoretical analysis. The process is analyzed by comparing the
configurational entropy of the system with the corresponding to a fully aligned
system, whose calculation reduces to the 1D case. The results obtained (1)
allow to estimate the minimum value of k which leads to the formation of a
nematic phase and provide an interesting interpretation of this critical value;
(2) provide numerical evidence on the existence of a second phase transition
(from a nematic to a non-nematic state) occurring at density close to 1 and (3)
allow to test the predictions of the main theoretical models developed to treat
the polymers adsorption problem.Comment: 14 pages, 6 figures. Accepted for publication in JSTA
Critical behavior of self-assembled rigid rods on triangular and honeycomb lattices
Using Monte Carlo simulations and finite-size scaling analysis, the critical
behavior of self-assembled rigid rods on triangular and honeycomb lattices at
intermediate density has been studied. The system is composed of monomers with
two attractive (sticky) poles that, by decreasing temperature or increasing
density, polymerize reversibly into chains with three allowed directions and,
at the same time, undergo a continuous isotropic-nematic (IN) transition. The
determination of the critical exponents, along with the behavior of Binder
cumulants, indicate that the IN transition belongs to the q=1 Potts
universality class.Comment: 6 pages, 5 figure
Critical behavior of long straight rigid rods on two-dimensional lattices: Theory and Monte Carlo simulations
The critical behavior of long straight rigid rods of length (-mers) on
square and triangular lattices at intermediate density has been studied. A
nematic phase, characterized by a big domain of parallel -mers, was found.
This ordered phase is separated from the isotropic state by a continuous
transition occurring at a intermediate density . Two analytical
techniques were combined with Monte Carlo simulations to predict the dependence
of on , being . The first involves
simple geometrical arguments, while the second is based on entropy
considerations. Our analysis allowed us also to determine the minimum value of
(), which allows the formation of a nematic phase on a
triangular lattice.Comment: 23 pages, 5 figures, to appear in The Journal of Chemical Physic
Study of the one-dimensional off-lattice hot-monomer reaction model
Hot monomers are particles having a transient mobility (a ballistic flight)
prior to being definitely absorbed on a surface. After arriving at a surface,
the excess energy coming from the kinetic energy in the gas phase is dissipated
through degrees of freedom parallel to the surface plane. In this paper we
study the hot monomer-monomer adsorption-reaction process on a continuum
(off-lattice) one-dimensional space by means of Monte Carlo simulations. The
system exhibits second-order irreversible phase transition between a reactive
and saturated (absorbing) phases which belong to the directed percolation (DP)
universality class. This result is interpreted by means of a coarse-grained
Langevin description which allows as to extend the DP conjecture to transitions
occurring in continuous media.Comment: 13 pages, 5 figures, final version to appear in J. Phys.
Determination of the Critical Exponents for the Isotropic-Nematic Phase Transition in a System of Long Rods on Two-dimensional Lattices: Universality of the Transition
Monte Carlo simulations and finite-size scaling analysis have been carried
out to study the critical behavior and universality for the isotropic-nematic
phase transition in a system of long straight rigid rods of length
(-mers) on two-dimensional lattices. The nematic phase, characterized by a
big domain of parallel -mers, is separated from the isotropic state by a
continuous transition occurring at a finite density. The determination of the
critical exponents, along with the behavior of Binder cumulants, indicate that
the transition belongs to the 2D Ising universality class for square lattices
and the three-state Potts universality class for triangular lattices.Comment: 7 pages, 8 figures, uses epl2.cls, to appear in Europhysics Letter
Phase diagram of self-assembled rigid rods on two-dimensional lattices: Theory and Monte Carlo simulations
Monte Carlo simulations and finite-size scaling analysis have been carried
out to study the critical behavior in a two-dimensional system of particles
with two bonding sites that, by decreasing temperature or increasing density,
polymerize reversibly into chains with discrete orientational degrees of
freedom and, at the same time, undergo a continuous isotropic-nematic (IN)
transition. A complete phase diagram was obtained as a function of temperature
and density. The numerical results were compared with mean field (MF) and real
space renormalization group (RSRG) analytical predictions about the IN
transformation. While the RSRG approach supports the continuous nature of the
transition, the MF solution predicts a first-order transition line and a
tricritical point, at variance with the simulation results.Comment: 12 pages, 10 figures, supplementary informatio
- …