LOCALIZED ELECTRONIC SURFACE STATES IN METALLIC STRUCTURES

2018 ◽  
Vol 25 (05) ◽  
pp. 1850101 ◽  
Author(s):  
A. BELAYADI ◽  
B. BOURAHLA ◽  
F. MEKIDECHE-CHAFA
Keyword(s):  
Interatomic Potential ◽  
Atomic Orbital ◽  
Tight Binding ◽  
Surface States ◽  
Localized States ◽  
High Symmetry ◽  
Metallic Structures ◽  
Text Type ◽  
Type Orbital ◽  
Electronic Surface

We present theoretical models to study the localized electronic surface states in metallic structures. The materials under study have been chosen with different types of cubic meshes, fcc, sc and bcc. The calculation method used is closely related to the Linear Combination of Atomic Orbitals (LCAO) in the tight-binding method. We consider three cases: each of the atoms is described by a single atomic orbital of [Formula: see text]-, [Formula: see text]- and [Formula: see text]-type orbitals. In order to solve the rectangular secular equations of the systems under study, the phase field matching method is involved. In particular, we apply our approach to calculate the localized electronic surface states of some metals: (i) Chromium and Silver having, respectively, bcc and fcc structure and described as [Formula: see text]-type orbital. (ii) Nickel with sc crystallization and described by [Formula: see text]-type orbital. (iii) Palladium (Pd) given in fcc crystallization and described by [Formula: see text]-type orbital. The obtained results illustrate spatial edge effects between the bulk modes and the localized electronic states of the metallic surfaces over the three orientations of high symmetry path. We observe many localized states above and below the bulk band range. In addition, the relaxation effect on the surface layer has been investigated to compute the localized electronic surface state in this case and illustrate the lift of the degeneracy compared to the first calculations based on an ordered surface. The spacing geometry caused by the relaxation on the surface has been determined by using the Molecular dynamic algorithm and Morse interatomic potential.

AN APPROACH BASED ON LANDAUER–BÜTTIKER FORMALISM TO COMPUTE THE ELECTRONIC LOCALIZED STATES AT SURFACE BOUNDARIES

2019 ◽  
Vol 27 (06) ◽  
pp. 1950164
Author(s):  
ADEL BELAYADI
Keyword(s):  
Tight Binding ◽  
Three Dimensional ◽  
Surface States ◽  
Relaxation Effect ◽  
Matching Theory ◽  
Localized States ◽  
Hamiltonian Matrix ◽  
Inhomogeneous System ◽  
Tight Binding Approximation ◽  
Characteristic Features

In this contribution, we provide a theoretical model to study the effect of different cutting edges on the appearance of localized electronic states. The system under study is a three-dimensional atomic chain that ends with an open cut forming a semi-infinite structured layer in the (1 0 0), (1 1 0) and (1 1 1) directions. We investigate the surface electronic characteristics of the monoatomic chain of a simple cube (sc), orthorhombic (orth), and tetragonal (tetr) structures. We have adopted in our approach the tight-binding approximation to build up the surface Hamiltonian matrix. Additionally, the number of secular equation, at the surface, has been determined by using phase field matching theory (FPMT). In fact, the Hamiltonian system obtained from different cutting orientations provides an inhomogeneous system. To solve the surface eigenvalue problem, we integrate the calculation of the scattering reflection probabilities as given in Landauer–Büttiker formalism. Next, based on the computed scattering probabilities, we build up the surface core states which provide the surface Hamiltonian matrix which can be solved numerically. Our model calculation has been applied to the following elements: (i) fluorite (F), manganese (Mn), polonium (Po), bromine (Br), indium (I), tin (Sn), and protactinium (Pa). The results emphasize the influence of cutting direction on the electronic characteristic of surface and on the scale of energy values. We report the appearance of new electronic curves that characterize the surface states. Those surface states are localized down, within, and above the bulk spectrum. They also provide different characteristic features, of the metals under study, in a given cutting orientation. Furthermore, we have integrated the calculation of non-structured cuts on the outer layers. The relaxation effect on the surface is a standard process which leads to stabilize the changes in the internal energy until the equilibrium. The spacing geometry caused by the relaxation on the surface could be determined by using the molecular dynamic algorithm. We account in this case the lift of degeneracy and the rise of additional localized branches within and outside the bulk range.

Computing the surface electronic states on the (100), (110) and (111) surfaces of FCC monatomic crystals

2021 ◽  
pp. 2150066
Author(s):  
Boualem Bourahla ◽  
Adel Belayadi
Keyword(s):  
Tight Binding ◽  
Relaxation Effect ◽  
Localized States ◽  
Quantum Scattering ◽  
Hamiltonian Matrix ◽  
Face Centered Cubic ◽  
Surface Band ◽  
Text Type ◽  
Scattering Coefficients ◽  
The Impact

In this study, we carry out a simulation of the surface band structures for face-centered cubic (fcc) leads that end up in (100), (110) and (111) surfaces. The surface Hamiltonian matrix is constructed from tight-binding approach and the secular equations of the surface eigenvalue problem. The solution of the problem is performed by integrating the Landauer–Büttiker formalism (LBF) in the phase field matching approach (PFMA). The LBF provides the quantum scattering properties and the PFMA connects the bulk modes to those of the surface based on the quantum scattering coefficients. The combination of these methods allows calculating the electronic bands in the three directions mentioned above. We report the results of ordered slabs for Ag, described as [Formula: see text]-like orbital and Ni given as [Formula: see text]-type orbitals. To show the impact of expanding the crystal wavefunction, we reveal the calculation of the localized states for Rh, Cu, Pt given as [Formula: see text]-type orbitals as first calculation then [Formula: see text]-coupling orbitals as second calculation. The results of the nonordered slabs are applied to Pd and Ir. Cutting the crystals affects the internal energy of the surface atoms, which will be subject to a relaxation effect until equilibrium is achieved.

Electronic surface states in GaAs/Ga1 − xAlxAs superlattice: effect of surface location

Vacuum ◽  
1995 ◽  
Vol 46 (5-6) ◽  
pp. 459-463 ◽  
Author(s):  
M Stȩślicka ◽  
R Kucharczyk ◽  
EH El Boudouti ◽  
B Djafari-Rouhani ◽  
ML Bah ◽  
...  
Keyword(s):  
Surface States ◽  
Surface Location ◽  
Electronic Surface ◽  
Effect Of Surface

ZERO AND FINITE TEMPERATURE STUDY OF SINGLE FULLERENE CAGES AND CARBON “ONIONS” — GEOMETRY AND SHAPE

1993 ◽  
Vol 07 (29n30) ◽  
pp. 1883-1895 ◽  
Author(s):  
A. MAITI ◽  
C.J. BRABEC ◽  
J. BERNHOLC
Keyword(s):  
Interatomic Potential ◽  
Critical Size ◽  
Tight Binding ◽  
Configurational Entropy ◽  
Electronic Structure Calculations ◽  
Carbon Onions ◽  
Three Body ◽  
Structure Calculations ◽  
Scaling Arguments

Scaling arguments are used to show that above a critical size of several thousand atoms, there is a stability crossover from single to multilayer cages. Conjugate gradient minimization using a classical three-body interatomic potential, as well as tight-binding electronic structure calculations yield ground-state configurations for large fullerene shells that are polyhedral with clearly faceted geometry. The structure, energetics and configurational entropy associated with low-energy defects are calculated and the number of defects estimated as a function of temperature. The role of these thermally generated defects on the shape of large fullerenes is investigated in order to explain the nearly spherical shapes of the newly discovered carbon “onions”.

scholarly journals Covalent assembly of a two-dimensional molecular “sponge” on a Cu(111) surface: confined electronic surface states in open and closed pores

2014 ◽  
Vol 50 (57) ◽  
pp. 7628-7631 ◽  
Author(s):  
Aneliia Shchyrba ◽  
Susanne C. Martens ◽  
Christian Wäckerlin ◽  
Manfred Matena ◽  
Toni Ivas ◽  
...  
Keyword(s):  
Surface States ◽  
Two Dimensional ◽  
New Class ◽  
Trimesic Acid ◽  
Electronic Surface

We present a new class of on-surface covalent reactions, formed between diborylene-3,4,9,10-tetraaminoperylene and trimesic acid on Cu(111), which gives rise to a porous 2D-‘sponge’.

Critique of the tight-binding method: Ideal vacancy and surface states

1981 ◽  
Vol 23 (8) ◽  
pp. 4063-4075 ◽  
Author(s):  
J. B. Krieger ◽  
Pinchus M. Laufer
Keyword(s):  
Tight Binding ◽  
Surface States ◽  
Tight Binding Method

Luminescent Amorphous Silicon Layers

1997 ◽  
Vol 486 ◽  
Author(s):  
G. Allan ◽  
C. Delerue ◽  
M. Lannoo
Keyword(s):  
Electronic Structure ◽  
Amorphous Silicon ◽  
Radiative Recombination ◽  
Crystalline Silicon ◽  
Tight Binding ◽  
Blue Shift ◽  
Localized States ◽  
Structure Model ◽  
Radiative Recombination Rate ◽  
Tight Binding Approximation

AbstractThe electronic structure of amorphous silicon layers has been calculated within the empirical tight binding approximation using the Wooten-Winer-Weaire atomic structure model. We predict an important blue shift due to the confinement for layer thickness below 3 nm and we compare with crystalline silicon layers. The radiative recombination rate is enhanced by the disorder and the confinement but remains quite small. The comparison of our results with experimental results shows that the density of defects and localized states in the studied samples must be quite small.

Sign in / Sign up

Export Citation Format

Share Document