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.

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.

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 Ab-Initio Multicenter Tight-Binding Model for Molecular Dynamics Simulations

1988 ◽  
Vol 141 ◽  
Author(s):  
Otto F. Sankey ◽  
David J. Niklewski
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Local Density ◽  
Tight Binding ◽  
Real Space ◽  
Hamiltonian Matrix ◽  
Binding Model ◽  
Annealing Study ◽  
Total Energies ◽  
Dynamics Simulations

AbstractA new, approximate method has been developed for computing total energies and forces for a variety of applications including molecular dynamics simulations of covalent materials. The method is tight-binding-like and is based on the local density approximation within the pseudopotential scheme. Slightly excited pseudo-atomic-orbitals are used, and the tight-binding Hamiltonian matrix is obtained in real space. The method is used to find the total energies for five crystalline phases of Si and the Si 2 molecule. Excellent agreement is found with experiment. A molecular dynamics simulated annealing study has been performed on the Si 3 molecule to determine the ground state configuration.

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.

Analysis of the structure of the surface local density of states at the Fermi level: an application of the surface Green function matching method

1989 ◽  
Vol 67 (9) ◽  
pp. 841-844 ◽  
Author(s):  
R. Baquero ◽  
L. Quiroga ◽  
A. Camacho
Keyword(s):  
Charge Transfer ◽  
Local Density ◽  
Tight Binding ◽  
Ferromagnetic Behavior ◽  
Local Density Of States ◽  
Matching Method ◽  
Full Agreement ◽  
Surface Band ◽  
Surface Green Function ◽  
Theory And Experiment

We use a tight-binding description of the bands of bulk vanadium to set a surface-band structure. We show that knowledge of the s–d charge transfer in the surface layer is very important to be able to reproduce the ferromagnetic behavior of the (100) vanadium surface. We use the surface Stoner criterion of Allan to determine the acceptable values for the s–d charge transfer. There is no full agreement between theory and experiment on the magnetic properties of (100) vanadium at present.

Tight-Binding Study of the {211} Σ=3 Grain Boundary in Cubic Silicon-Carbide

1994 ◽  
Vol 339 ◽  
Author(s):  
M. Kohyama ◽  
R. Yamamoto
Keyword(s):  
Grain Boundaries ◽  
Electronic Structures ◽  
Tight Binding ◽  
The Self ◽  
Localized States ◽  
General Definition ◽  
Self Consistent ◽  
Tight Binding Method ◽  
Definition Of ◽  
Cubic Silicon Carbide

ABSTRACTIn grain boundaries in compound semiconductors such as SiC, the interface stoichiometry and the wrong bonds between like atoms are of much importance. Firstly, a general definition of the interface stoichiometry in such grain boundaries has been discussed. Secondly, the atomic and electronic structures of the {211} Σ=3 boundary in SiC have been examined by using the self-consistent tight-binding method, based on the atomic models with bonding networks similar to those in the models of the same boundary in Si or Ge. The wrong bonds have significant effects through the large electrostatic repulsion and the generation of localized states as well as those in the {122} Σ=9 boundary in SiC. And the different bond lengths of the wrong bonds very much affect the local bond distortions at the interfaces, which determines the relative stability among the present models.

A SELF-CONSISTENT-CHARGE DENSITY-FUNCTIONAL TIGHT-BINDING THEORY BASED MOLECULAR DYNAMICS SIMULATION OF A ZWITTERIONIC GLYCINE IN AN EXPLICIT WATER ENVIRONMENT

2013 ◽  
Vol 12 (04) ◽  
pp. 1350019 ◽  
Author(s):  
Y. ZHAI ◽  
Y. L. ZHAO
Keyword(s):  
Molecular Dynamics ◽  
Amino Acids ◽  
Charge Density ◽  
Density Functional ◽  
Water Environment ◽  
Tight Binding ◽  
Water Molecules ◽  
Binding Theory ◽  
Self Consistent ◽  
The Impact

A zwitterionic glycine (zGLY) is adopted as an example to study the impact of water environment (310 H2O molecules) on the molecular structure and energetics using a self-consistent-charge density-functional tight-binding theory based molecular dynamics (SCC-DFTB/MD) method. It is found that maximal eight hydrogen bonds could be formed simultaneously between eight water molecules and the zGLY. The ability of the COO- terminal to adsorb water molecules is stronger than the [Formula: see text] terminal with respect to hydrogen bonding with more water molecules and exhibits lower adiabatic adsorption energies. The zGLY's intramolecular hydrogen bond appeared unpredictably, without involving any proton transfer and generally helpful for enhancing the system stability. Water molecules play an important role to stabilize the zwitterionic amino acids and restrain the proton migration from the [Formula: see text] to the COO− group. Our results show that the SCC-DFTB/MD method could successfully describe geometry dynamical evolutions and energetics of biomolecules in a nanoscale simulation with the presence of a large number of water molecules. Our study not only verified the feasibility of a QM level methodology for describing the aqueous states of biochemical molecules, but also gave a clear evidence for the impact of water environment on amino acids.

Stability and Structural Transition of Gold Nanowires under Their Own Surface Stresses

2004 ◽  
Vol 854 ◽  
Author(s):  
Ken Gall ◽  
Michael Haftel ◽  
Jiankuai Diao ◽  
Martin L. Dunn ◽  
Noam Bernstein ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Tight Binding ◽  
Gold Nanowires ◽  
Face Centered Cubic ◽  
First Principle ◽  
Local Energy Minimum ◽  
Surface Stresses ◽  
Embedded Atom ◽  
Theoretical Approaches ◽  
Face Centered

ABSTRACTFirst-principle, tight binding, and semi-empirical embedded atom calculations are used to investigate a tetragonal phase transformation in gold nanowires. As wire diameter is decreased, tight binding and modified embedded atom simulations predict a surface-stress-induced phase transformation from a face-centered-cubic (fcc) <100> nanowire into a body-centered-tetragonal (bct) nanowire. In bulk gold, all theoretical approaches predict a local energy minimum at the bct phase, but tight binding and first principle calculations predict elastic instability of the bulk bct phase. The predicted existence of the stable bct phase in the nanowires is thus attributed to constraint from surface stresses. The results demonstrate that surface stresses are theoretically capable of inducing phase transformation and subsequent phase stability in nanometer scale metallic wires under appropriate conditions.

57Fe Mössbauer isomer shifts in random face-centered cubic Fe–Ni alloys: Experiment versus electronic structure calculations

1992 ◽  
Vol 70 (12) ◽  
pp. 1241-1243 ◽  
Author(s):  
D. G. Rancourt ◽  
J. Y. Ping ◽  
M.-Z. Dang
Keyword(s):  
Tight Binding ◽  
Stability Limit ◽  
Quantitative Agreement ◽  
Face Centered Cubic ◽  
Linear Variation ◽  
Ni Alloys ◽  
Volume Dependence ◽  
Experiment Versus ◽  
Face Centered ◽  
Structure Calculations

Measured 57Fe-isomer shifts for face-centered cubic FeyNi1−y alloys show a linear variation with ∂1S/∂y = +0.10 mm s−1 up to [Formula: see text] followed by a plateau at [Formula: see text], up to the structural stability limit at [Formula: see text]. This is in disagreement with recent ab initio calculations, however, the increase at [Formula: see text] is in quantitative agreement with an older modified tight-binding approach in which the increase arises from an atomic volume dependence. The plateau is an anomaly that sets in at the same composition as that at which the saturation moments start to deviate from the Slater–Pauling curve.

Tetragonal Phase Transformation in Gold Nanowires

2004 ◽  
Vol 127 (4) ◽  
pp. 417-422 ◽  
Author(s):  
Ken Gall ◽  
Jiankuai Diao ◽  
Martin L. Dunn ◽  
Michael Haftel ◽  
Noam Bernstein ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Tetragonal Phase ◽  
Tight Binding ◽  
Gold Nanowires ◽  
Face Centered Cubic ◽  
First Principle ◽  
Local Energy Minimum ◽  
Surface Stresses ◽  
Embedded Atom ◽  
Theoretical Approaches

First principle, tight binding, and semi-empirical embedded atom calculations are used to investigate a tetragonal phase transformation in gold nanowires. As wire diameter is decreased, tight binding and modified embedded atom simulations predict a surface-stress-induced phase transformation from a face-centered-cubic (fcc) ⟨100⟩ nanowire into a body-centered-tetragonal (bct) nanowire. In bulk gold, all theoretical approaches predict a local energy minimum at the bct phase, but tight binding and first principle calculations predict elastic instability of the bulk bct phase. The predicted existence of the stable bct phase in the nanowires is thus attributed to constraint from surface stresses. The results demonstrate that surface stresses are theoretically capable of inducing phase transformation and subsequent phase stability in nanometer scale metallic wires under appropriate conditions.

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