Investigation of the Finite Size Properties of the Ising Model Under Various Boundary Conditions

The one-dimensional Ising model with various boundary conditions is considered. Exact expressions for the thermodynamic and magnetic properties of the model using different kinds of boundary conditions [Dirichlet (D), Neumann (N), and a combination of Neumann–Dirichlet (ND)] are presented in the absence (presence) of a magnetic field. The finite-size scaling functions for internal energy, heat capacity, entropy, magnetisation, and magnetic susceptibility are derived and analysed as function of the temperature and the field. We show that the properties of the one-dimensional Ising model is affected by the finite size of the system and the imposed boundary conditions. The thermodynamic limit in which the finite-size functions approach the bulk case is also discussed.

Ab initio investigation of the optical properties of layered MoSxSe(2−x) (0 ≤ x ≤ 2): By GGA and mBJ approaches

Based on the density functional theory (DFT) and using the generalized gradient approximation (GGA) and GGA-mBJ approximations, the electronic and optical properties of the bulk and mono-layer Molybdenum sulphoselenide MoS[Formula: see text]Se[Formula: see text] ([Formula: see text]) are calculated. In both bulk and mono-layer cases, the energy gap decreases by increasing the density of the Se atom, so that the reduction in the mono-layer case is more observable than the bulk case. Also, the variation of the exchange-correlation (XC) potential has the maximum and minimum effects on the bulk MoS2 and the mono-layer MoSe2 cases, respectively. The static dielectric function of MoS2 in the [Formula: see text] as well as its optical conductivity is less than the other two compounds. In the mono-layer case along [Formula: see text]-direction, the first response to the incident photon belongs to MoS2 in the infrared region, while the other two compounds respond in the edge of the visible area. The intensity of the MoSSe response, unlike its bulk case, is less than the other compounds. Along [Formula: see text]-direction, the first response is observed in the visible area. The remarkable point is that the optical stability in the bulk case is more than that in the mono-layer case.

Cooperative strings and glassy interfaces

We introduce a minimal theory of glass formation based on the ideas of molecular crowding and resultant string-like cooperative rearrangement, and address the effects of free interfaces. In the bulk case, we obtain a scaling expression for the number of particles taking part in cooperative strings, and we recover the Adam–Gibbs description of glassy dynamics. Then, by including thermal dilatation, the Vogel–Fulcher–Tammann relation is derived. Moreover, the random and string-like characters of the cooperative rearrangement allow us to predict a temperature-dependent expression for the cooperative length ξ of bulk relaxation. Finally, we explore the influence of sample boundaries when the system size becomes comparable to ξ. The theory is in agreement with measurements of the glass-transition temperature of thin polymer films, and allows quantification of the temperature-dependent thickness hm of the interfacial mobile layer.

Concentrational restrictions for race track memories based on permalloy

In using the fully relativistic versions of the Screened Korringa-Kohn-Rostoker method and of the Kubo-Greenwod equation domain wall resistivities at the equilibrium domain wall width are calculated for NicFe1-c. It is found that in comparison to the corresponding "bulk" case only between about 0.6¡Ü c<1 the anisotropic magnetoresistance is reduced in the presence of a domain wall sufficiently enough in order to be of practical use for potential race track memories. Around 80% Ni this reduction amount to remarkable 16%!

Magnetic X-Ray Resonant Scattering from a Dysprosium Epitaxial Film

ABSTRACTMagnetic X-Ray resonant scattering performed at the Dysprosium Lni absorption edge permits to study the magnetic behaviour of a 3000 Å thick Dy film. The development of an helical magnetic order gives rise to intense magnetic resonant harmonics. The energy dependence of the resonant intensity has been investigated and presents a double resonance at the second harmonic measured in the σ-π geometry. The accurate thermal variation of the turn angle and of the c-parameter is given. These evolutions reveal the stabilisation of the helical phase in the Dysprosium film compared to the bulk case.

Structural Properties of the Ion-Dipole Model of Electrolyte Solutions in the Bulk and Near a Charged Hard Wall.Application of the Truncated Optimized Cluster Series

An ion-dipole model of electrolyte solutions in the bulk case and near a charged or uncharged hard wall is considered. A method to derive the terms of optimized cluster expansions for the distribution functions of ions and dipoles which provides a set of approximations beyond the mean spherical approximation is given. The third cluster coefficient approximation is investigated

Pair correlation function in a fluid with density inhomogeneities: results of the Percus‒Yevick and hypernetted chain approximations for hard spheres near a hard wall

Solutions for the pair correlation function and density profile of a system of hard spheres near a hard wall are obtained by using the Percus‒Yevick and hypernetted chain approximations, generalized for inhomogeneous fluids. The Percus‒Yevick (PY) results are similar in accuracy to those obtained for the bulk fluid. The PY pair correlation function is generally too small near contact but quite good overall. The hypernetted chain (h. n. c.) results are difficult to obtain numerically and are poorer than in the bulk. Often the h. n. c. pair correlations are too small at contact, in contrast to the bulk case where they are too large, although there are configurations where the contact values of the pair correlation function are too large. Nearly always the error in the h. n. c. results is much worse than is the case for the bulk. Both approximations are qualitatively satisfactory in that they predict the correct asymmetries between the values of the pair correlation functions for pairs of hard spheres whose line of centres is parallel or normal to the surface of the wall.