Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userLiquid-Vapor Transition and Critical Behavior of The Ultrasoft Restricted Primitive Model of Polyelectrolytes : a Monte Carlo Study
174
0
0.0
(
0
)
Added by
Jean-Michel Caillol
Publication date
2014
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
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.
rate research
Read More
Reassessment of the critical temperature and density of the restricted primitive model of an ionic fluid by Monte Carlo simulations performed for system sizes with linear dimension up to $L/sigma=34$ and sampling of $sim 10^9$ trial moves leads to $T^*_c=0.04917 pm 0.00002$ and $rho_c^* =0.080 pm 0.005$. Finite size scaling analysis based in the Bruce-Wilding procedure gives critical exponents in agreement with those of the 3d Ising universality class. An analysis similar to that proposed by Orkoulas et al [Phys. Rev. E 63, 051507 (2001)], not relying on an a priori knowledge of the universality class, leads to an unaccurate estimate of $T_c^*$ and to unexpected behavior of the specific heat and value of the critical exponent ratio $gamma/ u$.
Via a combination of molecular dynamics (MD) simulations and finite-size scaling (FSS) analysis, we study dynamic critical phenomena for the vapor-liquid transition in a three dimensional Lennard-Jones system. The phase behavior of the model, including the critical point, have been obtained via the Monte Carlo simulations. The transport properties, viz., the bulk viscosity and the thermal conductivity, are calculated via the Green-Kubo relations, by taking inputs from the MD simulations in the microcanonical ensemble. The critical singularities of these quantities are estimated via the FSS method. The results thus obtained are in nice agreement with the predictions of the dynamic renormalization group and mode-coupling theories.
We investigate the critical relaxational dynamics of the S=1/2 Heisenberg ferromagnet on a simple cubic lattice within the Handscomb prescription on which it is a diagrammatic series expansion of the partition function that is computed by means of a Monte Carlo procedure. Using a phenomenological renormalization group analysis of graph quantities related to the spin susceptibility and order parameter, we obtain precise estimates for the critical exponents relations $gamma / u = 1.98pm 0.01 $ and $beta / u = 0.512 pm 0.002$ and for the Curie temperature $k_BT_c/J = 1.6778 pm 0.0002$. The critical correlation time of both energy and susceptibility is also computed. We found that the number of Monte Carlo steps needed to generate uncorrelated diagram configurations scales with the systems volume. We estimate the efficiency of the Handscomb method comparing its ability in dealing with the critical slowing down with that of other quantum and classical Monte Carlo prescriptions.
We have performed Monte Carlo simulations to investigate the temperature dependence of the ordering of the side chains of the X-shape liquid crystal molecules which are arranged in a hexagonal array. Each hexagon contains six side chains, one from each side of the hexagon. Each liquid crystal molecule has two, dissimilar, side chains, one that contains silicon and one containing fluorine. Like chains attract each other more strongly than unlike chains and this drives an order-disorder transition. The system is frustrated because it is not possible to find a configuration in which all the hexagons are occupied by either all silicon or all fluorine chains. There are two phase transitions. If only pairwise interactions are included it is found that there is a novel fluctuating phase between the disordered phase and the fully ordered ground state. This did not agree with the experiments where an intermediate phase was seen that had long range order on one of the three sublattices. Agreement was found when the calculations were modified to include attractive three body interactions between the silicon chains.
Systems of particles in a confining potential exhibit a spatially dependent density which fundamentally alters the nature of phase transitions that occur. A specific instance of this situation, which is being extensively explored currently, concerns the properties of ultra-cold, optically trapped atoms. Of interest is how the superfluid-insulator transition is modified by the inhomogeneity, and, indeed, the extent to which a sharp transition survives at all. This paper explores a classical analog of these systems, the Blume-Capel model with a spatially varying single ion anisotropy and/or temperature gradient. We present results both for the nature of the critical properties and for the validity of the local density approximation which is often used to model the inhomogeneous case. We compare situations when the underlying uniform transition is first and second order.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
