Orbitals and bands at metal surfaces: photoemission from the {110} surface of tungsten

1981 ◽  
Vol 376 (1767) ◽  
pp. 565-583 ◽  
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
Surface State ◽  
Photon Emission ◽  
Tight Binding ◽  
Tight Binding Approximation ◽  
The Third ◽  
Surface Brillouin Zone ◽  
Orbital Character ◽  
Bulk Band

The electronic structure of the {110} surface of tungsten has been investigated by using angle-resolved photoemission. A surface state has been identified and characterized throughout the surface Brillouin zone (s. B. z.). Its dispersion is found to correlate with the projected band gap between the third and fourth bands of the tungsten bulk band structure. It is identified by comparison with Inglesfield’s calculation as having predominantly m = 1 d-orbital character. With photon energies of 21.2 and 40.8 eV, intense photoemission from the surface state is only observed after surface Umklapp, whereas, with 16.8 eV, photon emission is observed in both the first and second s. B. zs. The applicability of the tight-binding approximation to the elucidation of the electronic structure of a metal surface is examined with particular reference to this surface state. A qualitative analysis of the observed photoemission intensities is consistent with emission from a tungsten e g orbital that is hybridized with e g orbitals on neighbouring atoms.

Empirical Tight-Binding Applied to Silicon Nanoclusters

1997 ◽  
Vol 491 ◽  
Author(s):  
G. Allan ◽  
C. Delerue ◽  
M. Lannoo
Keyword(s):  
Band Structure ◽  
Nearest Neighbor ◽  
Good Description ◽  
Tight Binding ◽  
Localized States ◽  
Basis Set ◽  
Band Structure Calculation ◽  
Minimal Basis ◽  
Tight Binding Approximation ◽  
Bulk Band

ABSTRACTThe calculation of the electronic structure of silicon nanostructures is used to discuss the accuracy of results obtained by the tight-binding method. We first show that the level of refinement of the tight-binding approximation must be adapted to the calculated property. For example, an accurate description of both the valence and conduction bands which can be achieved with a 3rd-nearest neighbor approximation is necessary to calculate the variation of the gap energy with the silicon crystallite size. The sp3s* model which gives a bad description of the conduction band underestimates the confinement energy but can give good results when it is used to determine the variation of the crystallite band gap with pressure. To study Si-III (BC-8) nanocrystallites, we show that a good description of the bulk band structure can be obtained with non-orthogonal tight-binding but due to the large number of nearest neighbors one must take analytical variations of the parameter with interatomic distances. The parameters involved in these expressions can be easily fitted to the bulk band structures using the k-point symmetry without requiring the use of group theory. Finally we discuss the effect of increasing the size of the minimal-basis set and we show that it would be possible to get the values of the tight-binding parameters from a first-principles localized states band structure calculation avoiding the fit to the energy dispersion curves.

CHANGES INDUCED IN THE SURFACE ELECTRONIC STRUCTURE OF Be(0001) AFTER Si ADSORPTION

2002 ◽  
Vol 09 (02) ◽  
pp. 687-691
Author(s):  
L. I. JOHANSSON ◽  
C. VIROJANADARA ◽  
T. BALASUBRAMANIAN
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
Band Gap ◽  
Electronic Properties ◽  
Surface State ◽  
Core Level ◽  
Clean Surface ◽  
Core Level Spectrum ◽  
Surface Band ◽  
Surface Electronic Structure

A study of effects induced in the Be 1s core level spectrum and in the surface band structure after Si adsorption on Be(0001) is reported. The changes in the Be 1s spectrum are quite dramatic. The number of resolvable surface components and the magnitude of the shifts do decrease and the relative intensities of the shifted components are drastically different compared to the clean surface. The surface band structure is also strongly affected after Si adsorption and annealing. At [Formula: see text] the surface state is found to move down from 2.8 to 4.1 eV. The band also splits at around 0.5 Å-1 along both the [Formula: see text] and [Formula: see text] directions. At [Formula: see text] and beyond [Formula: see text] only one surface state is observed in the band gap instead of the two for the clean surface. Our findings indicate that a fairly small amount of Si in the outer atomic layers strongly modifies the electronic properties of these layers.

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.

Local Electronic Structure and Short-Range Order in a Computer Simulated Amorphous Metal

1991 ◽  
Vol 02 (01) ◽  
pp. 232-237 ◽  
Author(s):  
A.Ya. BELENKII ◽  
M.A. FRADKIN
Keyword(s):  
Electronic Structure ◽  
Short Range ◽  
Short Range Order ◽  
Local Density ◽  
Tight Binding ◽  
Amorphous Metal ◽  
Range Order ◽  
Tight Binding Approximation ◽  
Electronic Parameters ◽  
Local Electronic Structure

The relationship between topological short-range order and a local electronic structure was analyzed in the computer model of an amorphous metal. The model, obtained by means of the original self-consistent cluster simulation procedure was studied with the use of Voronoi tesselation, the distribution of the atomic level stresses and the icosahedral order parameters. It was found that a marked correlation exists within 2 atomic parameter groups, one of which corresponds to the local dilatation and the other to the spherical symmetry distortion. The local density of electronic d-states (DOS) and the distribution of the electronic parameters was analyzed. The local electronic structure, calculated within the tight-binding approximation, appears to depend on the local atomic order by two-fold means: the interatomic distances decrease leads to the increase of the local bandwidth, and the icosahedral configuration distortion reduces the DOS at the Fermi level. The study of the local configurations stability shows, that the most stable configurations are the slightly distorted icosahedra.

Band structure of silicene in the tight binding approximation

2015 ◽  
Vol 121 (1) ◽  
pp. 115-121 ◽  
Author(s):  
A. V. Gert ◽  
M. O. Nestoklon ◽  
I. N. Yassievich
Keyword(s):  
Band Structure ◽  
Tight Binding ◽  
Tight Binding Approximation

A Tight-Binding Hamiltonian for the High-Temperature Superconductor YBa2Cu3O7

1988 ◽  
Vol 141 ◽  
Author(s):  
M.J. DeWeert ◽  
D.A. Papaconstantopoulos ◽  
W.E. Pickett
Keyword(s):  
Electronic Structure ◽  
High Temperature ◽  
Band Structure ◽  
Potential Application ◽  
Oxygen Vacancies ◽  
High Temperature Superconductor ◽  
Tight Binding ◽  
Coherent Potential Approximation ◽  
Potential Approximation

AbstractWe present a highly accurate tight-binding parametrization of the LAPW band structure of the high-temperature superconductor YBa2Cu3O7, discuss the methodology used in obtaining this fit, and its potential application to a Tight-Binding Coherent-Potential Approximation (TB-CPA) calculation of the effects of oxygen vacancies on the electronic structure.

scholarly journals Photoemission Spectroscopy of Single Crystal HTSC Materials: A Fermi Liquid Electronic Structure

1989 ◽  
Vol 156 ◽  
Author(s):  
A. J. Arko ◽  
R. S. List ◽  
R. J. Bartlett ◽  
S. W. Cheong ◽  
C. G. Olson ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
Single Crystal ◽  
Fermi Liquid ◽  
Wide Band ◽  
Photoemission Spectroscopy ◽  
Correlation Effects ◽  
Band Dispersion ◽  
Valence Bands ◽  
Orbital Character

ABSTRACTPhotoemission spectra from HTSC materials ( primarily 123 -type ), cleaved and measured at 20K, reveal a rich DOS structure which compares favorably with a calculated band structure, except for a residual 0.5 eV shift which may reflect some correlation effects. Band dispersion is observed throughout the valence bands, with clear evidence for a 0.2 eV wide band dispersing through EF. The orbital character at EF is a mix of Cu-3d and O-2p. There is unambiguous evidence for a large BCS-like gap (2Δ≥ 4kTc).

Tight Binding Modelling of Energy Band Structure in Nitride Heterostructures

2008 ◽  
Vol 8 (2) ◽  
pp. 540-548 ◽  
Author(s):  
Özden Akıncı ◽  
H. Hakan Gürel ◽  
Hilmi Ünlü
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
Valence Band ◽  
Nearest Neighbor ◽  
Good Description ◽  
Energy Levels ◽  
Tight Binding ◽  
Binding Theory ◽  
Orbit Splitting ◽  
Atomic Energy Levels

We studied the electronic structure of group III–V nitride ternary/binary heterostructures by using a semi-empirical sp3s* tight binding theory, parametrized to provide accurate description of both valence and conductions bands. It is shown that the sp3s* basis, along with the second nearest neighbor (2NN) interactions, spin-orbit splitting of cation and anion atoms, and nonlinear composition variations of atomic energy levels and bond length of ternary, is sufficient to describe the electronic structure of III–V ternary/binary nitride heterostructures. Comparison with experiment shows that tight binding theory provides good description of band structure of III–V nitride semiconductors. The effect of interface strain on valence band offsets in the conventional Al1−xGaxN/GaN and In1−xGaxN/GaN and dilute GaAs1−xNx/GaAs nitride heterostructures is found to be linear function of composition for the entire composition range (0 ≤ x ≤ 1) because of smaller valence band deformations.

scholarly journals Tight–Binding Analysis of Electronic Structure of Germanene Sheet and Nanoribbons Including Stone-Wales Defect

2021 ◽  
Author(s):  
Komeil Rahmani ◽  
Saeed Mohammadi
Keyword(s):  
Band Structure ◽  
Band Gap ◽  
Energy Band ◽  
Dirac Point ◽  
Tight Binding ◽  
Topological Defects ◽  
Energy Band Structure ◽  
Fermi Velocity ◽  
Tight Binding Approximation ◽  
Wales Defect

Abstract In this paper, we investigate the electronic characteristics of germanene using the tight binding approximation. Germanene as the germanium-based analogue of graphene has attracted much research interest in recent years. Our analysis is focused on the pristine sheet of germanene as well as defective monolayer. The Stone-Wales defect, which is one of the most common topological defects in such structures, is considered in this work. Not only the infinite sheet of germanene but also the germanene nanoribbons in different orientations are analyzed. The obtained results show that applying the Stone–Wales defect into the germanene monolayer changes the energy band structure; the E-k curves around the Dirac point are no longer linear, a band gap is opened, and the Fermi velocity is reduced to half of that of defect-free germanene. In the case of nanoribbon structures, the armchair germanene nanoribbons with nanoribbon widths of 3p and 3p+1 reveal the semiconductor behaviour. However, armchair germanene nanoribbon with width of 3p+2 is semi-metal. After applying the Stone–Wales defect, the band gap of armchair germanene nanoribbons with widths of 3p and 3p+1 is reduced and it is increased for the width of 3p+2. Furthermore, there is no band gap in the energy band structure of zigzag germanene nanoribbon and the metallic behaviour is obvious.

scholarly journals Symmetry-adapted tight-binding electronic structure analysis of carbon nanotubes with defects, kinks, twist, and stretch

2020 ◽  
pp. 108128652096183
Author(s):  
Soumya Mukherjee ◽  
Hossein Pourmatin ◽  
Yang Wang ◽  
Timothy Breitzman ◽  
Kaushik Dayal
Keyword(s):  
Carbon Nanotubes ◽  
Electronic Structure ◽  
Band Structure ◽  
Tight Binding ◽  
Numerical Approach ◽  
Computational Method ◽  
Computational Domain ◽  
Perfectly Matched Layers ◽  
Vacancy Defects ◽  
Semiconducting Nanotubes

In this paper, a symmetry-adapted method is applied to examine the influence of deformation and defects on the electronic structure and band structure in carbon nanotubes. First, the symmetry-adapted approach is used to develop the analog of Bloch waves. Building on this, the technique of perfectly matched layers is applied to develop a method to truncate the computational domain of electronic structure calculations without spurious size effects. This provides an efficient and accurate numerical approach to compute the electronic structure and electromechanics of defects in nanotubes. The computational method is applied to study the effect of twist, stretch, and bending, with and without various types of defects, on the band structure of nanotubes. Specifically, the effect of stretch and twist on band structure in defect-free conducting and semiconducting nanotubes is examined, and the interaction with vacancy defects is elucidated. Next, the effect of localized bending or kinking on the electronic structure is studied. Finally, the paper examines the effect of 5–8–5 Stone–Wales defects. In all of these settings, the perfectly matched layer method enables the calculation of localized non-propagating defect modes with energies in the bandgap of the defect-free nanotube.

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