scholarly journals О магнитных состояниях зигзагообразной кромки графеновой наноленты

2020 ◽  
Vol 62 (1) ◽  
pp. 180
Author(s):  
С.Ю. Давыдов
Keyword(s):  
Electronic Structure ◽  
Density Of States ◽  
Structural Model ◽  
Magnetic Moments ◽  
Nearest Neighbors ◽  
Metal Substrate ◽  
Band Spectrum ◽  
Zigzag Edge ◽  
Anderson Hamiltonian ◽  
Occupation Numbers

Abstract Using a simple structural model and the multicenter Anderson Hamiltonian, Green’s functions are obtained for the atoms of the zigzag edge of an epitaxial graphene nanoribbon. The electronic structure of the free nanoribbon is discussed in detail. Specifically, expressions for the band spectrum and density of states are found and estimates of the occupation numbers and magnetic moments are given. For a nanoribbon strongly bonded to a metal substrate, the criteria for the appearance of magnetic moments are determined. As it is shown for both free and epitaxial nanoribbons, the probability of the appearance of magnetic moments and their magnitude for zigzag edge atoms that have two nearest neighbors is higher than for atoms with three nearest neighbors.

scholarly journals Цепочечная модель декорирования зигзагообразной кромки графена

2019 ◽  
Vol 53 (1) ◽  
pp. 83
Author(s):  
С.Ю. Давыдов
Keyword(s):  
Energy Band ◽  
Structural Model ◽  
Metal Substrate ◽  
Band Spectrum ◽  
Brick Wall ◽  
Zigzag Edge ◽  
Occupation Numbers ◽  
Graphene Lattice ◽  
Densities Of States ◽  
Analytical Expressions

AbstractFor a brick-wall-like lattice topologically equivalent to the graphene lattice, a simple structural model of a zigzag edge decorated with particles is constructed. Analytical expressions for the energy band spectrum, densities of states, and occupation numbers of the graphene–particles system are derived for a system in the free state and for a system formed on a metal substrate.

scholarly journals О декорировании зигзагообразной кромки эпитаксиального графена

2019 ◽  
Vol 61 (1) ◽  
pp. 186
Author(s):  
С.Ю. Давыдов
Keyword(s):  
Electronic Structure ◽  
Graphene Sheet ◽  
Cluster Model ◽  
Dipole Interaction ◽  
Metal Substrate ◽  
Zigzag Edge ◽  
Occupation Numbers ◽  
Local Densities ◽  
Analytical Expressions

AbstractTwo approaches are proposed to the problem of the coupling of adsorbed particles with atoms of a zigzag edge of graphene formed on a metal substrate. The first approach is based on the Kalkstein and Soven scheme, which makes it possible to determine the electronic structure of a semi-infinite graphene sheet. The second approach is based on a cluster model of a zigzag edge. Analytical expressions are obtained for the local densities of the system’s states and the occupation numbers of a carbon adatom and an adparticle. The case of an isolated adparticle is considered in detail, and a method of taking into account the dipole–dipole interaction of particles aligned along the edge is proposed.

scholarly journals О декорировании зигзагообразных краев наноленты эпитаксиального графена

2019 ◽  
Vol 61 (3) ◽  
pp. 610
Author(s):  
С.Ю. Давыдов
Keyword(s):  
Density Of States ◽  
Tight Binding ◽  
Free State ◽  
Band Spectrum ◽  
Adsorption Complex ◽  
Chain Model ◽  
Double Chain ◽  
Occupation Numbers ◽  
A Chain ◽  
Analytical Expressions

AbstractA double-chain model of an epitaxial graphene nanoribbon, the zigzag edges of which are decorated with foreign adparticles, has been proposed. The substrate is assumed to be a metal. Analytical expressions for the Green’s functions of carbon adatoms and adparticles are obtained. The band spectrum for the free state is determined, and the approximation of the density of states is proposed. Analytical expressions for the occupation numbers in the mode of tight binding between the adsorption complex and the substrate are presented. A chain of carbon adatoms decorated with adparticles (epicarbyne) is considered.

Effects of vanadium impurity on TiO2 properties

2015 ◽  
Vol 29 (15) ◽  
pp. 1550094 ◽  
Author(s):  
Arvids Stashans ◽  
Jairo Escobar
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Density Of States ◽  
Density Functional ◽  
Magnetic Moments ◽  
Equilibrium Geometry ◽  
Dft Studies ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Atomic Rearrangement

Our present work is based on the density functional theory (DFT) studies of TiO 2 crystals doped with V impurities. Both rutile and anatase structures have been considered within the present research and different defect concentrations have been used as well. Our calculations reveal equilibrium geometry of the system showing atomic rearrangement around the point defect being mainly inward with respect to the impurity. Magnetism and electronic structure based on the density of states (DOS) patterns for both rutile and anatase crystals have been obtained and discussed in detail. It is shown that local magnetic moments arise mainly from the 3d states of the impurity atom with some admixture of 2p states from the vanadium-nearest O atoms.

scholarly journals Точно решаемая модель графеновой наноленты с зигзагообразными краями

2020 ◽  
Vol 54 (2) ◽  
pp. 170
Author(s):  
С.Ю. Давыдов ◽  
А.В. Зубов
Keyword(s):  
Structural Model ◽  
Graphene Nanoribbon ◽  
Zigzag Edge ◽  
Occupation Numbers ◽  
Densities Of States ◽  
Local Densities ◽  
Analytical Expressions

Abstract Exact analytical expressions for the local densities of states and the occupation numbers of atoms at the zigzag edge of a graphene nanoribbon are derived in the context of a simple structural model. As an example of application of the results, the problem of a Koster–Slater defect is considered.

ELECTRONIC STRUCTURE OF YBa2(Cu1−xFex)3O7

1993 ◽  
Vol 07 (01n03) ◽  
pp. 170-173
Author(s):  
V. CRISAN ◽  
A. VERNES ◽  
V. POPESCU ◽  
L. DULCA ◽  
D. KAPUSI
Keyword(s):  
Electronic Structure ◽  
Fermi Level ◽  
Density Of States ◽  
Copper Atom ◽  
Opposite Effect ◽  
Recursive Method ◽  
Electron Orbital ◽  
Occupation Numbers ◽  
Model Hamiltonian ◽  
Orbital Occupation

The density of states (DOS) at the Fermi level, (EF), for the 123 superconductor doped with iron was computed. The LCAO model hamiltonian and the Haydock recursive method were used. The iron atoms were located only in one of the copper atom positions Cu1 or Cu2 or in both of them with the same probability. The substitution of Fe in Cu1 positions increased the DOS at the Fermi level as x increased but the substitutions in the Cu2 positions had an opposite effect. In both cases the O2 and O3 positions are inequivalent. When the replacement of copper atoms is produced with the same probability in Cu1 and Cu2 positions the DOS at EF decreases as x increases. The DOS at EF and the electron orbital occupation numbers for O2 and O3 have the same behaviour as the lattice parameters, a and b.

scholarly journals Цепочечная модель зигзагообразного контакта латеральных графеноподобных гетероструктур

2018 ◽  
Vol 44 (21) ◽  
pp. 55
Author(s):  
С.Ю. Давыдов
Keyword(s):  
Boron Nitride ◽  
Density Of States ◽  
Structural Model ◽  
Hexagonal Boron Nitride ◽  
Two Dimensional ◽  
Occupation Numbers ◽  
Densities Of States ◽  
Spectrum Density ◽  
Analytical Expressions ◽  
Good Agreement

AbstractA simple structural model is proposed for the zigzag interface formed by contacting two-dimensional graphene-like compounds AB and CD (both free and formed on a metal). For the graphene–hexagonal boron nitride system, analytical expressions for the electron spectrum, density of states, and atom occupation numbers at the interface are obtained. The results of calculating the densities of states and occupation numbers within two alternative approximations are in good agreement.

Vacancy effects on the electronic structure of MgO compound

2015 ◽  
Vol 29 (25) ◽  
pp. 1550147 ◽  
Author(s):  
B. Merabet ◽  
S. Kacimi ◽  
A. Mir ◽  
M. Azzouz ◽  
A. Zaoui
Keyword(s):  
Electronic Structure ◽  
Oxygen Vacancy ◽  
Room Temperature ◽  
Magnetic Moments ◽  
Nearest Neighbors ◽  
Full Potential ◽  
Vacant Site ◽  
Spin Magnetic Moment ◽  
Augmented Plane Wave ◽  
Linearized Augmented Plane Wave

We have investigated the possibility to find [Formula: see text] ferromagnetism (FM) in the non-stoichiometric [Formula: see text] compound using the full potential linearized augmented plane wave [Formula: see text] method. We have examined the oxygen vacancy effect on the electronic structure of [Formula: see text] compound realizing the 128 atoms supercell. Our calculations predict that the cation vacancies cause the FM in [Formula: see text], where the magnetism is often created by the oxygen atoms nearest neighbors of the Mg vacant site, with a spin magnetic moment of 0.21 [Formula: see text]B/atom. We have reported a strong evidence of the existence of FM at room temperature, as we extended our studies to demonstrate the ability to induce intrinsic magnetic moments in MgO with cationic vacancies (Mg).

Study on Electronic Properties of ZnO Doped with Cr, Mn and Co by First Principles

2012 ◽  
Vol 512-515 ◽  
pp. 1257-1262
Author(s):  
Xing Gao ◽  
Guo You Gan ◽  
Ji Kang Yan ◽  
Jing Hong Du ◽  
Jia Min Zhang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Density Of States ◽  
Electronic Property ◽  
First Principles ◽  
Density Functional ◽  
Magnetic Moments ◽  
Functional Theory ◽  
Spin Dependent Scattering ◽  
Zno Crystal

A method using first principles and pseudopotentials based on density functional theory is applied to calculate the electronic structure and the density of states of ZnO doped with Cr, Mn and Co. Portion of Zn atoms in ZnO crystal randomly substituted by Mn, Cr or Co elements, the electronic structure of Cr2+, Mn2+and Co2+change into 3d4, 3d5and 3d7, which result in giving rise to localized magnetic moments in ZnO. It was concluded that electronic property of ZnO is not only related with levels of electrons, but also associated with spin, spin-dependent scattering and spin-dependent hopping conductivity are maybe two important mechanism.

Relation Between Local Structure, Electric Dipole and Charge Carrier Dynamics in DHICA Melanin, a Model for Biocompatible Semiconductors

2019 ◽  
Author(s):  
Micaela Matta ◽  
Alessandro Pezzella ◽  
Alessandro Troisi
Keyword(s):  
Electronic Structure ◽  
Degrees Of Freedom ◽  
Structural Model ◽  
Computational Study ◽  
Oxidative Polymerization ◽  
Radical Scavenging ◽  
Charge Carriers ◽  
Electronic Charge ◽  
Polymer Semiconductors ◽  
Synthetic Pigments

<div><div><div><p>Eumelanins are a family of natural and synthetic pigments obtained by oxidative polymerization of their natural precursors: 5,6 dihydroxyindole and its 2-carboxy derivative (DHICA). The simultaneous presence of ionic and electronic charge carriers makes these pigments promising materials for applications in bioelectronics. In this computational study we build a structural model of DHICA melanin considering the interplay between its many degrees of freedom, then we examine the electronic structure of representative oligomers. We find that a non-vanishing dipole along the polymer chain sets this system apart from conventional polymer semiconductors, determining its electronic structure, reactivity toward oxidation and localization of the charge carriers. Our work sheds light on previously unnoticed features of DHICA melanin that not only fit well with its radical scavenging and photoprotective properties, but open new perspectives towards understanding and tuning charge transport in this class of materials.<br></p></div></div></div>

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