Energetics and electronic structure of point defects associated with oxygen excess at a tilt boundary of ZnO

2000 ◽  
Vol 15 (10) ◽  
pp. 2167-2175 ◽  
Author(s):  
Fumiyasu Oba ◽  
Hirohiko Adachi ◽  
Isao Tanaka
Keyword(s):  
Electronic Structure ◽  
Point Defects ◽  
First Principles ◽  
Electronic States ◽  
Tilt Boundary ◽  
Oxygen Excess ◽  
Zno Varistors ◽  
Formation Energies ◽  
Defect Species ◽  
Static Lattice

The formation energies and electronic structure of zinc vacancies and oxygen interstitials at a tilt boundary of ZnO were investigated by a combination of static lattice and first-principles molecular orbital methods. For both of the defect species, the formation energies were lower than those of the bulk defects at certain sites in the grain boundary. The defects with low formation energies formed electronic states close to the top of the valence band. The interfacial electronic states observed experimentally in ZnO varistors cannot be explained solely by the point defects associated with the oxygen excess: the effects of impurities should be significant for the states.

The Properties of a Na-Doped Twist Boundary in SrTiO3 from First Principles

2002 ◽  
Vol 751 ◽  
Author(s):  
Roope K. Astala ◽  
Paul D. Bristowe
Keyword(s):  
Electronic Structure ◽  
Grain Boundary ◽  
Plane Wave ◽  
First Principles ◽  
Driving Force ◽  
Chemical Potential ◽  
Twist Boundary ◽  
Atomic Displacements ◽  
Formation Energies ◽  
Oxygen Chemical Potential

ABSTRACTThe segregation of Nasr impurities to a Σ = 5 [001] twist boundary in SrTiO3 is studied using DFT-based plane-wave pseudopotential techniques. The formation energies of the impurities are calculated as a function of oxygen chemical potential and electron chemical potential. The results indicate a strong driving force for segregation to the boundary and that the Na impurities exhibit acceptor-like behaviour. The atomic displacements caused by the impurities are small both in the bulk and at the grain boundary. Based on the results a model is suggested in which Nasr segregation is driven by soft relaxation of the electronic structure.

scholarly journals The Effect of Defect Disorder on the Electronic Structure of Rutile TiO2-x

2006 ◽  
Vol 251-252 ◽  
pp. 1-12 ◽  
Author(s):  
Faruque M. Hossain ◽  
Graeme E. Murch ◽  
L. Sheppard ◽  
Janusz Nowotny
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Point Defects ◽  
Density Functional ◽  
Defect Formation ◽  
Energy Levels ◽  
Defect Energy ◽  
Defect Disorder ◽  
Effect Of Oxygen ◽  
Formation Energies

The purpose of this work is to study the effect of bulk point defects on the electronic structure of rutile TiO2. The paper is focused on the effect of oxygen nonstoichiometry in the form of oxygen vacancies, Ti interstitials and Ti vacancies and related defect disorder on the band gap width and on the local energy levels inside the band gap. Ab initio density functional theory is used to calculate the formation energies of such intrinsic defects and to detect the positions of these defect induced energy levels in order to visualize the tendency of forming local mid-gap bands. Apart from the formation energy of the Ti vacancies (where experimental data do not exist) our calculated results of the defect formation energies are in fair agreement with the experimental results and the defect energy levels consistently support the experimental observations. The calculated results indicate that the exact position of defect energy levels depends on the estimated band gap and also the charge state of the point defects of TiO2.

Effects of Point Defects on Electronic Structure and Optical Properties of Al0.5Ga0.5N Nanosheets: First-principles Investigation

2019 ◽  
Vol 40 (8) ◽  
pp. 979-986
Author(s):  
屈艺谱 QU Yi-pu ◽  
陈 雪 CHEN Xue ◽  
王 芳 WANG Fang ◽  
刘玉怀 LIU Yu-huai
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Point Defects ◽  
First Principles

First Principles Study of Point Defects in Uranium Dioxide

2007 ◽  
Vol 561-565 ◽  
pp. 1971-1974 ◽  
Author(s):  
Ying Chen ◽  
Misako Iwasawa ◽  
Yasunori Kaneta ◽  
Toshiharu Ohnuma ◽  
Hua Yun Geng ◽  
...  
Keyword(s):  
Point Defects ◽  
First Principles ◽  
Defect Formation ◽  
Lattice Relaxation ◽  
Atomic Displacement ◽  
Grain Structure ◽  
First Principles Calculations ◽  
Fine Grain ◽  
Unit Cells ◽  
Formation Energies

To clarify the origin of a characteristic fine grain structure formed under the high burn-up of the nuclear fuel, the comprehensive first-principles calculations for UO2 containing various types of point defect have been performed by the PAW-GGA+U with lattice relaxation for supercells containing 1, 2 and 8 unit cells of UO2. The electronic structure, the atomic displacement and the defect formation energies of defective systems are obtained, and the effects of supercell size on these properties are discussed. Based on this relatively high precise self-consistent formation energies dataset, thermodynamic properties of various types of point defects in UO2 are further investigated in the framework of the point defects model.

First principles study of defects in solid electrolyte lithium thiophosphate Li7P3S11

2011 ◽  
Vol 1331 ◽  
Author(s):  
Ka Xiong ◽  
Weichao Wang ◽  
Roberto Longo Pazos ◽  
Kyeongjae Cho
Keyword(s):  
Electronic Structure ◽  
Solid Electrolyte ◽  
Band Gap ◽  
Electronic Properties ◽  
First Principles ◽  
Wide Band ◽  
Ion Conductivity ◽  
First Principles Calculations ◽  
Wide Band Gap ◽  
Formation Energies

ABSTRACTWe investigate the electronic structure of interstitial Li and Li vacancy in Li7P3S11 by first principles calculations. We find that Li7P3S11 is a good insulator with a wide band gap of 3.5 eV. We find that the Li vacancy and interstitial Li+ ion do not introduce states in the band gap hence they do not deteriorate the electronic properties of Li7P3S11. The calculated formation energies of Li vacancies are much larger than those of Li interstitials, indicating that the ion conductivity may arise from the migration of interstitial Li.

scholarly journals First-Principles Study on Various Point Defects Formed by Hydrogen and Helium Atoms in Tungsten

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Qiang Zhao ◽  
Zheng Zhang ◽  
Yang Li ◽  
Xiaoping Ouyang
Keyword(s):  
Point Defects ◽  
First Principles ◽  
Formation Energy ◽  
Interstitial Site ◽  
First Principles Calculation ◽  
Hydrogen Atoms ◽  
Substitutional Site ◽  
Helium Atoms ◽  
Tetrahedral Interstitial Site ◽  
Formation Energies

The different point defects formed by two hydrogen atoms or two helium atoms in tungsten were investigated through first-principles calculation. The energetically favorable site for a hydrogen atom is tetrahedral interstitial site while substitutional site is the most preferred site for a helium atom. The formation energies of two hydrogen or helium atoms are determined by their positions, and they are not simply 2 times the formation energy of a single hydrogen or helium atom’s defect. After relaxation, two adjacent hydrogen atoms are away from each other while helium atoms are close to each other. The reasons for the interaction between two hydrogen or helium atoms are also discussed.

First-Principles Study of π-Bonded (100) Planar Defects in Diamond

1998 ◽  
Vol 538 ◽  
Author(s):  
Peter Zapol ◽  
Larry A. Curtiss ◽  
Dieter M. Gruen
Keyword(s):  
Electronic Structure ◽  
Grain Boundary ◽  
First Principles ◽  
Density Functional ◽  
Single Point ◽  
High Energy ◽  
Dynamics Simulation ◽  
Functional Study ◽  
Planar Defects ◽  
Formation Energies

AbstractA periodic density functional study of the high-energy π-bonded (100) stacking fault in diamond that can serve as a prototype of a twist grain boundary has been carried out. Information on formation energies, geometries and the electronic structure has been obtained. A single point electronic structure calculation of a ∑5 twist grain boundary based on the geometry taken from a molecular dynamics simulation has also been performed.

FIRST-PRINCIPLES CALCULATION OF THE ELECTRONIC STRUCTURE AND MAGNETISM AT THE GRAPHENE/Ni(111) INTERFACE

2011 ◽  
Vol 25 (21) ◽  
pp. 2791-2800
Author(s):  
L. CHEN ◽  
Y. OUYANG ◽  
H. Z. PAN ◽  
Y. Y. SUN ◽  
Y. L. WANG
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Graphene Layer ◽  
Magnetic Moments ◽  
Electronic States ◽  
First Principles Calculation ◽  
Spintronic Devices ◽  
Ni Substrate ◽  
Spin Polarized ◽  
Atomic And Electronic Structure

A spin-polarized first-principles calculation of the atomic and electronic structure of the graphene/ Ni (111) interface is studied. The electronic structure of the graphene layer is strongly modified by interaction with the substrate and a behavior where magnetic moments are localized at the edges of nanoscale holes of isolated graphene does not happen in the defect-graphene/ Ni (111) system. The magnetic moment of the surface nickel atoms is lowered in the presence of the graphene layer and nanoscale holes of graphene, which control the strength of the hybridization between electronic states of graphene and Ni substrate. Our findings show that an electron spin in the graphene/ Ni (111) interface can be manipulated in a controlled way and have important implications for graphene-based spintronic devices.

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