A Simple Model for the Surface Phenomena

Abstract

The simplicity of the present model consists in the construction of the Hamiltonian based on the models of quasi-harmonic oscillators coupled to quasi-free electrons with the effective parameters which are estimated by means of the pseudoharmonic approach and coherent potential approximation, respectively. The geometry of a sample is determined by the topological disorder at the surface reflecting the surface roughness. The model is discussed in connection with the friction related to the melting and pre-melting phenomena. The backscattering of electrons seems to be a testing tool useful not only for decorated surfaces but also for quasi-liquid 1ayers.PACS numbers: 68.15.+t, 68.45.-v In troductionThe surface phenomena constitute one of the largest areas of interdisciplinary sciences such as physics, chemistry and mechanics, i.e. sciences representing different approaches to the description of the considered surface effects. The physical picture seems to be the leading one in the considerations which give in consequence the complete model constructed on the basis of complementary pictures obtained from the different approaches. Although the great number of papers dealing with the above problems resulted in the emergence of several specialized journals, many problems, however, remain still unsolved. The field is open for investigations and for new aspects of the surface properties to be discovered.The present contribution is devoted to the model describing the friction related to the melting and pre-melting phenomena as well as applicable to the diffuse low energy electron diffraction (diffuse LEED) which seems to be particularly interesting as the backscattering by a quasi-liquid layer growing on the surface. The coincidence of these two aspects is not only due to the common aspect of the research but, first of all, to the same background of these phenomena, namely, the behaviour of topological correlations at the surface.The role of tw osite occupancy was discussed in several papers in connection with a general treatment of the correlation problem [1,2] as well as in the "Permanent address:

Indirect RKKY interaction between localized magnetic moments in armchair graphene nanoribbons

“…The form of RKKY interaction, originally derived for bulk, metallic, three-dimensional systems, is sensitive to the geometry and dimensionality of the underlying system and is closely connected with the electronic structure of the host material. This opened the door for studies of RKKY coupling in low-dimensional systems [8][9][10][11][12][13][14][15] in particular thin films [16][17][18] at the crossover between three-and two-dimensions, or for pseudo-one-dimensional systems [19]. For instance, in metallic two-dimensional systems, RKKY coupling has been predicted to decay with distance according to J RKKY ∝ 1/r 2 .…”

Magnetic Properties of Thin Films Containing Itinerant Electrons Interacting with Localized Spins

“…In (23) E ,~ depends on the lattice structure and on the parameter a,, which can be obtained from the boundary conditions ( A -2 cos a,) TI,, + T2,, = 0 , ( A -2 cos a,) q,, + q-l,r = 0 , where A is the surface parameter depending on the interaction constants and the coordination number in the surface layer [44,451 and describing the influence of the distribution of the electronic density near the surface on the electron eigenvalues for thin films. The parameters T,, are taken in the general form [45],…”

Giant magnetoresistance in ultra-thin layers

“…In the distinguished direction (z-axis) perpendicular to the surface there appears asymmetry of electronic density caused by a lack of the potential sources which would be produced by the missing nearest neighbors in the boundary layers (cf. [6]). It is worth-while to notice that the electronic density distribution depends strongly on the boundary conditions and it can increase or decrease at the surfaces.…”