Defect Structure of Cobalt Monoxide: I, The Ideal Defect Model

1989 ◽  
Vol 72 (7) ◽  
pp. 1199-1207 ◽  
Author(s):  
Janusz Nowotny ◽  
Mieczyslaw Rekas
Keyword(s):  
Defect Structure ◽  
Defect Model ◽  
The Ideal

Theoretical Investigations of the Defect Structure for Ni3+ in ZnO

2011 ◽  
Vol 318 ◽  
pp. 41-45
Author(s):  
Zhi Hong Zhang ◽  
Shao Yi Wu ◽  
Shan Xiang Zhang
Keyword(s):  
Defect Structure ◽  
Impurity Center ◽  
Spin Hamiltonian ◽  
Theoretical Investigations ◽  
Ligand Orbital ◽  
High Valence State ◽  
Zno Crystal ◽  
Hamiltonian Parameters ◽  
Good Agreement ◽  
The Ideal

The defect structure for Ni3+ in ZnO crystal is theoretically investigated using the perturbation formulas of the spin Hamiltonian parameters for a 3d7 ion in trigonally distorted tetrahedra. In view of the significant covalency of the system due to the high valence state of Ni3+, the ligand orbital and spin-orbit coupling contributions are taken into account in a uniform way based on the cluster approach. The impurity Ni3+ is found not to occupy the ideal Zn2+ site in ZnO but to undergo the small axial displacement of about 0.044 Ǻ away from the oxygen triangle along the C3 axis. The theoretical spin Hamiltonian parameters based on the above impurity displacement show good agreement with the experimental data. The defect structure of this impurity center is compared with that for the similar Fe3+ in ZnO.

Neutron-Zwischenreflex-Scattering from Point Defects in Crystals

1986 ◽  
Vol 69 ◽  
Author(s):  
H. Dosch ◽  
J. Peisl
Keyword(s):  
Point Defects ◽  
Displacement Field ◽  
Defect Structure ◽  
Host Lattice ◽  
Local Defect ◽  
Defect Model ◽  
Defect Site ◽  
X Ray Scattering ◽  
Tetrahedral Sites ◽  
Diffuse Neutron

AbstractDiffuse neutron or x-ray scattering close to the Bragg peaks (Huang scattering) and far away from Bragg peaks (Zwischenreflex-scattering) supplies detailed information on point defects and small agglomerates in crystals [1]. The defect structure, i.e. the lattice location, the displacements of the near neighbours and the strength and symmetry of the long ranged displacement field can be determined. In order to demonstrate the power of this technique, we report on recent experimental results. Interstitially dissolved N and O in Nb are located on octahedral sites and create rather large displacements in their vicinity. Their long ranged displacement field shows the symmetry of the defect site. The light interstitials H and D in Nb are located on tetrahedral sites and their long ranged displacement field shows the symmetry of the host lattice. A rather complicated defect model is necessary in order to explain the local defect structure.

scholarly journals Дефекты и некоторые физические свойства номинально чистых и легированных цинком кристаллов ниобата лития

2021 ◽  
Vol 63 (8) ◽  
pp. 1132
Author(s):  
Н.А. Теплякова ◽  
М.В. Смирнов ◽  
Н.В. Сидоров ◽  
М.Н. Палатников
Keyword(s):  
Luminescence Intensity ◽  
Defect Structure ◽  
Zinc Concentration ◽  
Energy Levels ◽  
Visible Region ◽  
Small Energy ◽  
Photoinduced Light Scattering ◽  
Group Valence ◽  
Group Concentration ◽  
The Ideal

The features of defect structure and their influence on the properties of LiNbO3:Zn crystals, doped in a wide concentration range, including two concentration thresholds (at ~ 3.0 and ~ 6.8 mol. % ZnO in the melt), were studied by absorption IR spectroscopy in the region of OH--group valence vibrations, photoluminescence in the visible region of the spectrum, and photoinduced light scattering. In LiNbO3:Zn(0.004-2.01 mol. % ZnO) crystals the increase of zinc concentration led to increasing in the OH--group concentration and decreasing the luminescence intensity of luminescence centers associated with NbLi defects. Apparently, the latter was connected with the formation of small energy levels near the bottom of the conduction band as the zinc atoms displaced niobium atoms from the lithium positions in the ideal structure and the NbLi defect concentration decreased, respectively. In highly doped LiNbO3:Zn crystals (4.46-6.5 mol. % ZnO) and in the LiNbO3stoich(6.0 wt. % K2O) crystal there were lower OH--group concentration, the increase of band gap by 0.3-0.4 eV, and the increase of luminescence intensity in the green region of the spectrum due to the formation of new recombination channels compared to weakly doped crystals. In addition, in such crystals, the increase of proton conductivity was observed due to increasing in the concentration of interstitial hydrogen H+ and, as a result, the formation of many small acceptor levels near the valence band.

Investigations of the EPR Parameters and Local Structure for one Cu2+ Center in CdS

2008 ◽  
Vol 280-281 ◽  
pp. 15-20
Author(s):  
Li Hua Wei ◽  
Shao Yi Wu ◽  
Yue Xia Hu ◽  
Xue Feng Wang
Keyword(s):  
Experimental Data ◽  
Hyperfine Structure ◽  
Local Structure ◽  
Defect Structure ◽  
Reasonable Agreement ◽  
Cluster Approach ◽  
Epr Parameters ◽  
Structure Constants ◽  
Theoretical Results ◽  
The Ideal

The EPR g factors g// and g and the hyperfine structure constants for one substitutional Cu2+ center in CdS are theoretically investigated from the perturbation formulas of these parameters for a 3d9 ion under trigonally distorted tetrahedra. In view of the significant covalency of the [CuS4]6 cluster, the ligand contributions are taken into account on the basis of the cluster approach. According to the calculations, the impurity Cu2+ is found not to occupy exactly the ideal Cd2+ site but to suffer a small inward displacement 0.12 Å toward the ligand triangle along C3 axis. The theoretical results by considering the above impurity displacement show reasonable agreement with the experimental data. The defect structure of this Cu2+ center is also discussed.

Localization of Intracellular Antigens in thin Sections with Ferritin Labeled Antibody

1970 ◽  
Vol 28 ◽  
pp. 174-175
Author(s):  
M.S. Shahrabadi ◽  
T. Yamamoto
Keyword(s):  
Bovine Serum Albumin ◽  
Bovine Serum ◽  
Antigenic Determinants ◽  
Conjugate Prior ◽  
Thin Sections ◽  
Specific Attachment ◽  
Intracellular Antigen ◽  
Antigen Antibody ◽  
Ideal Method ◽  
The Ideal

The technique of labeling of macromolecules with ferritin conjugated antibody has been successfully used for extracellular antigen by means of staining the specimen with conjugate prior to fixation and embedding. However, the ideal method to determine the location of intracellular antigen would be to do the antigen-antibody reaction in thin sections. This technique contains inherent problems such as the destruction of antigenic determinants during fixation or embedding and the non-specific attachment of conjugate to the embedding media. Certain embedding media such as polyampholytes (2) or cross-linked bovine serum albumin (3) have been introduced to overcome some of these problems.

Criteria and Methods for Reliable Three-Dimensional Image Reconstruction

1974 ◽  
Vol 32 ◽  
pp. 330-331
Author(s):  
R. A. Crowther
Keyword(s):  
Image Reconstruction ◽  
Finite Number ◽  
Density Distribution ◽  
Electron Micrographs ◽  
Mathematical Problem ◽  
Three Dimensional ◽  
Ideal Case ◽  
Dimensional Image ◽  
General Object ◽  
The Ideal

The reconstruction of a three-dimensional image of a specimen from a set of electron micrographs reduces, under certain assumptions about the imaging process in the microscope, to the mathematical problem of reconstructing a density distribution from a set of its plane projections.In the absence of noise we can formulate a purely geometrical criterion, which, for a general object, fixes the resolution attainable from a given finite number of views in terms of the size of the object. For simplicity we take the ideal case of projections collected by a series of m equally spaced tilts about a single axis.

Electron Microscope Observations of Mechanical Metamorphism in Iron Meteorites

1970 ◽  
Vol 28 ◽  
pp. 488-489
Author(s):  
D. Faulkner ◽  
G.W. Lorimer ◽  
H.J. Axon
Keyword(s):  
Electron Microscope ◽  
Defect Structure ◽  
Shock Loading ◽  
List Type ◽  
Iron Meteorites

It is now generally accepted that meteorites are fragments produced by the collision of parent bodies of asteroidal dimensions. Optical metallographic evidence suggests that there exists a group of iron meteorites which exhibit structures similar to those observed in explosively shock loaded iron. It seems likely that shock loading of meteorites could be produced by preterrestrial impact of their parent bodies as mentioned above.We have therefore looked at the defect structure of one of these meteorites (Trenton) and compared the results with those made on a) an unshocked ‘standard’ meteorite (Canyon Diablo)b) an artificially shocked ‘standard’ meteorite (Canyon Diablo) andc) an artificially shocked specimen of pure α-iron.

X-Ray Analysis of Frozen Hydrated Sections:The Unconventional Approach

1982 ◽  
Vol 40 ◽  
pp. 754-757
Author(s):  
R. Beeuwkes ◽  
A. Saubermann ◽  
P. Echlin ◽  
S. Churchill
Keyword(s):  
Ratio Method ◽  
Frozen Sections ◽  
Technical Problems ◽  
Sample Handling ◽  
X Ray ◽  
Common Group ◽  
Ideal Method ◽  
Classic Paper ◽  
Physical Principles ◽  
The Ideal

Fifteen years ago, Hall described clearly the advantages of the thin section approach to biological x-ray microanalysis, and described clearly the ratio method for quantitive analysis in such preparations. In this now classic paper, he also made it clear that the ideal method of sample preparation would involve only freezing and sectioning at low temperature. Subsequently, Hall and his coworkers, as well as others, have applied themselves to the task of direct x-ray microanalysis of frozen sections. To achieve this goal, different methodological approachs have been developed as different groups sought solutions to a common group of technical problems. This report describes some of these problems and indicates the specific approaches and procedures developed by our group in order to overcome them. We acknowledge that the techniques evolved by our group are quite different from earlier approaches to cryomicrotomy and sample handling, hence the title of our paper. However, such departures from tradition have been based upon our attempt to apply basic physical principles to the processes involved. We feel we have demonstrated that such a break with tradition has valuable consequences.

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