674 research outputs found
Wetting on a spherical-shell substrate
No full textA density-functional theory for the wetting of an inert spherical-shell substrate by a single-component bulk vapor is developed, on the basis of the usual assumption that the pairwise intermolecular interaction is divided into a repulsive hard sphere and a weak attractive part. The substrate vapor-molecule pairwise interaction is also divided into a hard-wall repulsive interaction and a weak attractive tail. Choosing the attractive interactions properly, a second-order nonlinear functional differential equation results, which is solved numerically with appropriate boundary conditions. It is shown that the wetting layer, formed on the adsorbent, is either a thin or a thick film of finite thickness. Furthermore, in some cases the substrate is not at all wet. The wall-vapor and other interfacial tensions, the associated radii, and the principal tensors (the transverse pT(r) and normal pN(r)) are also calculated. The wall-vapor interface is mainly under tension (pN(r) > pT(r))
Wetting and structure of a fluid in a spherical cavity
No full textThe equilibrium local densities, structure, and wetting of a one-component fluid in a spherical cavity, of variable radius R, are determined, using density-functional theory, as functions of two parameters characterizing the system: the radius R and the cavity/fluid potential parameter [formula presented] The cavity acts as an external potential [formula presented] on the molecules of the confined fluid, the particles of which are of constant diameter d. The equilibrium density profile, as a result of strong confinement, develops peaks in the center of the cavity and/or close to the pore wall and, in certain situations, in other intermediate points; the cavity can also be liquid full, capillary condensation. © 2002 The American Physical Society
The Sherrington-Kirkpatrick spin glass model in the presence of a random field with a joint Gaussian probability density function for the exchange interactions and random fields
No full textThe magnetic systems with disorder form an important class of systems, which are under intensive studies, since they reflect real systems. Such a class of systems is the spin glass one, which combines randomness and frustration. The Sherrington-Kirkpatrick Ising spin glass with random couplings in the presence of a random magnetic field is investigated in detail within the framework of the replica method. The two random variables (exchange integral interaction and random magnetic field) are drawn from a joint Gaussian probability density function characterized by a correlation coefficient ρ. The thermodynamic properties and phase diagrams are studied with respect to the natural parameters of both random components of the system contained in the probability density. The de Almeida-Thouless line is explored as a function of temperature, ρ and other system parameters. The entropy for zero temperature as well as for non zero temperatures is partly negative or positive, acquiring positive branches as h0 increases. © 2013 Elsevier B.V. All rights reserved
Effective field theory for the Ising model with a fluctuating exchange integral in an asymmetric bimodal random magnetic field: A differential operator technique
No full textThe spin-1/2 Ising model on a square lattice, with fluctuating bond interactions between nearest neighbors and in the presence of a random magnetic field, is investigated within the framework of the effective field theory based on the use of the differential operator relation. The random field is drawn from the asymmetric and anisotropic bimodal probability distribution P( hi)=pδ(hi-h1)+qδ( hi+ch1), where the site probabilities p,q take on values within the interval [0,1] with the constraint p+q=1; hi is the random field variable with strength h1 and c the competition parameter, which is the ratio of the strength of the random magnetic field in the two principal directions +z and -z; c is considered to be positive resulting in competing random fields. The fluctuating bond is drawn from the symmetric but anisotropic bimodal probability distribution P(Jij)=12δ( Jij-(J+Δ))+δ(Jij-(J-Δ)), where J and Δ represent the average value and standard deviation of Jij, respectively. We estimate the transition temperatures, phase diagrams (for various values of the system's parameters c,p,h1,Δ), susceptibility, and equilibrium equation for magnetization, which is solved in order to determine the magnetization profile with respect to T and h1. © 2012 Elsevier B.V. All rights reserved
The random field Ising model with an asymmetric and anisotropic bimodal probability distribution
No full text
Monte Carlo analysis of the critical properties of the two-dimensional randomly bond-diluted Ising model via Wang–Landau algorithm
No full text
- …
