Theoretical Studies of Oxygen Vacancies in YBa2Cu3O7-y

1987 ◽  
Vol 99 ◽  
Author(s):  
Brent A. Richert ◽  
Roland E. Allen
Keyword(s):  
Electronic Structure ◽  
Density Of States ◽  
Fermi Energy ◽  
Oxygen Vacancies ◽  
Tight Binding ◽  
Theoretical Studies ◽  
Metal Atoms

ABSTRACTWe have performed semiempirical tight-binding calculations of the electronic structure of YBa2Cu3O7, with dand s orbitals included for all the metal atoms and p and sorbitals for oxygen. Here we report studies of oxygen vacancies on the O(1) chain sites in YBa2Cu3O7-y. The modification of the density of states ρ(E) and the shift of the Fermi energy Ep were calculated for 0 < y ≤ 1.0. The Fermi energy is found to increase monotonically with y, confirming the expectation that oxygen vacancies act as donors. Also, ρ(EF)is found to decrease with y.

First-principle investigation of electronic structure and mechanical properties of AlMgB14

2009 ◽  
Vol 1224 ◽  
Author(s):  
Liwen F Wan ◽  
Scott P Beckman
Keyword(s):  
Mechanical Properties ◽  
Electronic Structure ◽  
Ab Initio ◽  
Density Of States ◽  
Fermi Energy ◽  
First Principle ◽  
Metal Atoms ◽  
Structural And Electronic Properties ◽  
The Impact ◽  
Atomic And Electronic Structure

AbstractThe structural and electronic properties of AlMgB14 are investigated using ab initio methods. The impact of vacancies and electron doping on the crystal’s atomic and electronic structure is investigated. It is found that removing metal atoms does not influence the density of states, except for changes to the Fermi energy. The density of states of the off-stoichiometric Al0.75Mg0.75B14 crystal and the AlMgB14 crystal with five electrons removed are nearly identical. The removal of six electrons results in an 11% contraction in the crystal’s volume. This is associate with the removal of electrons from the B atoms’ 2p-states.

Tight Binding Modeling of Properties Related to Field Emission from Nanodiamond Clusters

2000 ◽  
Vol 621 ◽  
Author(s):  
Denis A. Areshkin ◽  
Olga A. Shenderova ◽  
Victor V. Zhirnov ◽  
Alexander F. Pal ◽  
John J. Hren ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Field Emission ◽  
Density Of States ◽  
Electron Affinity ◽  
Potential Distribution ◽  
Tight Binding ◽  
Matrix Elements ◽  
Energy States ◽  
Bulk Diamond ◽  
Modeling Of Properties

ABSTRACTThe electronic structure of nanodiamond clusters containing between 34 and 913 carbon atoms was calculated using a tight-binding Hamiltonian. All clusters had shapes represented by an octahedron with (111) facets with the top and the bottom vertices truncated to introduce (100) surfaces. The tight-binding Hamiltonian consisted of environment-dependent matrix elements, and C-H parameters fit to reproduce energy states of the cyclic C6 and methane. The calculations predict a density of states similar to bulk diamond for clusters with radii greater than ∼2.5nm, and insignificant differences in the potential distribution between the clusters and bulk diamond for radii greater than ∼1nm. Hydrogen passivated nanodiamond clusters are estimated to have an electron affinity of approximately -1.8 eV.

HYDROGEN BONDING IN DIAMOND: A COMPUTATIONAL STUDY

2006 ◽  
Vol 17 (07) ◽  
pp. 959-966 ◽  
Author(s):  
O. OFER ◽  
JOAN ADLER ◽  
A. HOFFMAN
Keyword(s):  
Density Of States ◽  
Fermi Energy ◽  
Computational Study ◽  
Tight Binding ◽  
Local Deformation ◽  
Electronic Energy ◽  
Hydrogen Atoms ◽  
High Hydrogen ◽  
New Energy ◽  
Energy States

We present tight binding molecular dynamics simulations of the diffusion and bonding of hydrogen in bulk diamond. The motion of hydrogen atoms and the resultant structural and electronic energy level changes are investigated. The hydrogen atoms were found to have a tendency to migrate to the surface layer of diamond, resulting in a local deformation of the lattice, creating new energy states above and below the Fermi energy in the bandgap of the diamond density of states. In the diamond bulk, at high hydrogen concentrations, vacancies created by a hydrogen atom are quickly filled with other hydrogen atoms causing a deformation of the diamond lattice, inducing H 2 formation. This creates new energy states above the Fermi energy and reduces the secondary bandgap of the diamond density of states.

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 Augmented Space Recursion Method for the Study of Electronic States of Binary Alloys

1970 ◽  
Vol 44 (3) ◽  
pp. 255-264
Author(s):  
M Abdus Salam ◽  
Kabir Ahmed ◽  
BP Barua ◽  
MSI Aziz
Keyword(s):  
Electronic Structure ◽  
Density Of States ◽  
Tight Binding ◽  
Electronic States ◽  
Density Of State ◽  
Recursion Method ◽  
Disordered Alloys ◽  
Lmto Method ◽  
Augmented Space ◽  
Space Formalism

We have studied here the electronic structure of pure random disordered alloys formed by Ni with Cu and Au at different ratios by using the linearized tight-binding muffin-tin Orbital (TB-LMTO) method. We also used the recursion technique together with augmented space formalism for increasing the efficiency and the accuracy to calculate the component projected density of states. From the density of state, we can understand the Fermi energy, magnetic moment and binding energy at different alloy compositions. The band structure can be calculated from here also. These studies are helpful for experimentalists and metallurgists in designing materials and alloys with specific properties. Key words: Electronic structure, Alloys, TB-LMTO, Density of states, Augmented space recursion   DOI: 10.3329/bjsir.v44i3. Bangladesh J. Sci. Ind. Res. 44(3), 255-264, 2009

ELECTRONIC STRUCTURE CALCULATIONS FOR MoSe2 USING EXTENDED HUCKEL TIGHT-BINDING METHOD

2004 ◽  
Vol 18 (01) ◽  
pp. 35-44 ◽  
Author(s):  
DONALD H. GALVAN
Keyword(s):  
Electronic Structure ◽  
Density Of States ◽  
Population Analysis ◽  
Tight Binding ◽  
Electronic Structure Calculations ◽  
Total Density ◽  
Mulliken Population Analysis ◽  
Energy Bands ◽  
Mulliken Population ◽  
Structure Calculations

To gain insight into the electronic properties of MoSe 2 (molybdenum selenide, also known as drysdallite), electronic structure calculations, total and projected density of states, crystal orbital overlap population and Mulliken population analysis were performed. The calculated energy bands depict a semiconductor behavior with a direct gap (at K) of 0.91 eV and an indirect gap (from Γ to K) of 3.6 eV, respectively. Total and projected density of states provided information about the contribution from each orbital of each atom to the total density of states. Moreover, the bonding strength between some atoms within the unit cell was obtained. Mulliken population analysis corroborates the electron filling of the Mo dz2 orbitals in agreement with another experimental and theoretical results.

Electronic Structures

2003 ◽  
Author(s):  
Toshiaki Enoki ◽  
Morinobu Endo ◽  
Masatsugu Suzuki
Keyword(s):  
Electronic Structure ◽  
Electronic Properties ◽  
Graphene Sheet ◽  
Fermi Energy ◽  
Reciprocal Lattice ◽  
Tight Binding ◽  
Electron System ◽  
Interlayer Interaction ◽  
Binding Model ◽  
Weak Interlayer

In the structure of graphite, graphene hexagon sheets are stacked in an AB stacking mode as shown in Figure 1.3. Such as mode is characterized by strong in-plane C-C bonds and weak interlayer interaction. This structural feature imparts two-dimensionality to its electronic structure. In the in-plane hexagon carbon network, the combination of sp2 σ- and π-bonds is the origin of the strong intralayer interaction, while the overlap of π-bonds between adjacent graphene sheets contributes to the weak interlayer interaction. In discussing the electronic properties around the Fermi energy, which is particularly important for the electronic structure of GICs, the π-electron orbitals play an essential role, giving graphite its unique properties. On the other hand, σ-bands, which have larger energy than π-bands, are located far from the Fermi energy. Thus they do not contribute to any serious change in the electronic properties when intercalates are introduced in the graphitic galleries. Here, we start with the electronic structure of graphite on the basis of the tight binding model. The discussion is first devoted to a graphene sheet, which is considered to be an infinite 2D hexagonal conjugated π-electron system (Wallace, 1947). Figure 5.la presents a unit cell of graphene sheet comprising two kinds of carbon atoms, α and β, where τ2 is the vector connecting the two atoms. The corresponding Brillouin zone in the reciprocal lattice is shown in Figure 5.1b.

Effects of Molecular Orientational Disorder on the Electronic Structure of K3C60: With the Inclusion of the Tangentially Directed C σ-Orbital

1998 ◽  
Vol 12 (32) ◽  
pp. 3521-3528
Author(s):  
Jing Lu ◽  
Xiangeng Zhao ◽  
Xinwei Zhang ◽  
Liyuan Zhang
Keyword(s):  
Electronic Structure ◽  
Fermi Level ◽  
Conduction Band ◽  
Density Of States ◽  
Tight Binding ◽  
Tight Binding Model ◽  
Orientational Disorder ◽  
Binding Model ◽  
Distance Dependence ◽  
Orbital Approximation

Effects of molecular orientational disorder on the electronic structure of K3C60 are studied using a tight-binding model in which both the 2s and 2p orbitals of C atoms are taken into account. Nearly free of the cut-off distance of the interculster interaction and the form of the distance dependence of the hopping parameters, the orientational disorder always smears out the structure in the conduction-band density of states (DOS), while the value of the DOS at the Fermi level (N(E F )) changes slightly upon disordering. These results are in excellent agreement with the earlier ones based on the single molecular orbital approximation.

Electronic Structure and Total-Energy of FeSi2 Pseudomorphic Phases

1993 ◽  
Vol 320 ◽  
Author(s):  
Leo Miglio ◽  
Giovanna Malegori
Keyword(s):  
Thin Films ◽  
Electronic Structure ◽  
Molecular Beam Epitaxy ◽  
Total Energy ◽  
Density Of States ◽  
Molecular Beam ◽  
Tight Binding ◽  
Binding Parameters ◽  
Annealing Temperatures ◽  
Β Phase

ABSTRACTBy fitting orthogonal tight binding parameters to the ab inlio bands of Calciumfluorite FeSi2 (γ-phase) and Cesiumcloride FeSi, we calculate the electronic structure (bands and density of states) and the total-energy of the semiconductive, orthorombic β-phase and the disordered, cubic one. The latter, the γ and the β nfigurations, have been recently observed at different annealing temperatures in thin films grown on Si (111) by Molecular Beam Epitaxy. The transferability of our method among different phases allows for a comparison of the cohesive energy curves which, in turn, supplies an interpretation of the relative stability and the growth kinetics.

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