A dislocation core in titanium dioxide and its electronic structure

RSC Advances ◽  
2015 ◽  
Vol 5 (24) ◽  
pp. 18506-18510 ◽  
Author(s):  
Rong Sun ◽  
Zhongchang Wang ◽  
Naoya Shibata ◽  
Yuichi Ikuhara
Keyword(s):  
Titanium Dioxide ◽  
Electronic Structure ◽  
Electric Conductivity ◽  
Dislocation Core ◽  
Core Structure ◽  
Atomic Resolution ◽  
The Core ◽  
Resolution Imaging

We provide a direct atomic-resolution imaging of the core structure of a dislocation in technologically important TiO2 and predict that every individual impurity-free dislocation exhibits electric conductivity in an otherwise insulating TiO2.

Computer Simulation Study of the Effects of Copper Precipitates on Dislocation Core Structure in Ferritic Steels

1996 ◽  
Vol 439 ◽  
Author(s):  
T. Harry ◽  
D. J. Bacon
Keyword(s):  
Dislocation Core ◽  
Alloy System ◽  
Lattice Parameter ◽  
Transformation Process ◽  
Core Structure ◽  
Metastable Equilibrium ◽  
Precipitate Size ◽  
Ferritic Steels ◽  
Interatomic Potentials ◽  
The Core

AbstractThe small, coherent BCC precipitates of copper that form during fast neutron irradiation of ferritic steels are an important component of in-service irradiation hardening. Many-body interatomic potentials for the Fe-Cu alloy system have been developed and used to simulate the atomic structure of the ½<111> screw dislocation in both pure a-iron and the metastable BCC phase of copper. In iron, the core has the well-known 3-fold form of atomic disregistry. In BCC copper, however, the core structure depends on the lattice parameter. At the metastable equilibrium value, the core is similar to that in iron, but as the lattice parameter is reduced, as in a precipitate, the core becomes delocalised by transformation of the copper. Simulation of dislocated crystals containing precipitates shows that the extent of this effect depends on precipitate size. The energy changes indicate a significant dislocation pinning effect due to this dislocation-induced precipitate transformation process.

The Core Structure of Dislocations in GaAs

1985 ◽  
Vol 62 ◽  
Author(s):  
B. C. De Cooman ◽  
K.-H. Kuesters ◽  
C. B. Carter
Keyword(s):  
High Stress ◽  
Dislocation Core ◽  
Core Structure ◽  
Screw Dislocations ◽  
The Core ◽  
Resolution Electron ◽  
Model Structures ◽  
High Resolution Electron Micrographs ◽  
Structural Aspects ◽  
Strong Asymmetry

ABSTRACTThe structural aspects of dislocations in GaAs which had been plastically deformed at high stress were studied by TEM. The glide of well-defined dislocations in their slip-plane was observed during the recombination-enchanced relaxation of the dislocations from their high-stress configuration. The strong asymmetry of dislocation velocity previously observed by other techniques is confirmed. High-resolution, electron micrographs of dissociated end-on screw dislocations were compared to computer simulated micrographs of model structures of the dislocation core. No definite conclusion regarding the exact core structure could be made due to the movement of the defects during the observation.

On non-glide stresses and their influence on the screw dislocation core in body-centred cubic metals. II. The core structure

1984 ◽  
Vol 392 (1802) ◽  
pp. 175-197 ◽  
Keyword(s):  
Stress Tensor ◽  
Screw Dislocation ◽  
Applied Stress ◽  
Elastic Strain ◽  
Elastic Anisotropy ◽  
Dislocation Core ◽  
Core Structure ◽  
Peierls Stress ◽  
The Core ◽  
Anisotropic Elastic

The change in core structure of the screw dislocation in a body-centred cubic lattice subjected to a general applied stress tensor is studied by means of computer simulation. The large variations observed are found not to be correlated with the applied stress, in that the same deformed core structure can be realized by many different combinations of stress components. Instead, the core structure is found to be characterized almost exclusively by the magnitude and orientation of the induced glide strain, with a much smaller dependence on the glide stress. This means that while the force acting on a dislocation is defined by the applied stress, it is the elastic strain within the lattice that determines the resistance to motion. This explains the anomalously large dependence of the Peierls stress upon non-glide components of the applied stress tensor. The Peierls stress varies strongly with the shape of the dislocation core, which depends upon the glide strain. However, the glide strain is in turn dependent on non-glide components of the applied stress by way of anisotropic elastic couplings. Therefore the Peierls stress is itself dependent on the non-glide stresses, to an extent governed by the elastic anisotropy. The possible origin of the strain-dependence of the core structure in elastic strain multiplet forces (equal and opposite generalized forces acting on the dislocation) is discussed briefly, as are implications for the phenomenon of ductile fracture.

scholarly journals Revealing and Controlling the Core of Screw Dislocations in BCC Metals

2021 ◽  
Author(s):  
Zhaoxuan Wu ◽  
Rui Wang ◽  
Lingyu Zhu ◽  
Subrahmanyam Pattamatta ◽  
David Srolov
Keyword(s):  
Dft Calculations ◽  
Density Functional ◽  
Dislocation Core ◽  
Core Structure ◽  
Valence Electron Concentration ◽  
Interatomic Potentials ◽  
Structure Transition ◽  
The Core ◽  
Bcc Metals ◽  
Dislocation Core Structure

Abstract Body-centred-cubic (BCC) transition metals (TMs) tend to be brittle at low temperatures, posing significant challenges in their processing and major concerns for damage tolerance in critical load-carrying applications. The brittleness is largely dictated by the screw dislocation core structure; the nature and control of which has remained a puzzle for nearly a century. Here, we introduce a universal model and a physics-based material index χ that guides the manipulation of dislocation core structure in all pure BCC metals and alloys. We show that the core structure, commonly classified as degenerate (D) or non-degenerate (ND), is governed by the energy difference between BCC and face-centred cubic (FCC) structures and χ robustly captures this key quantity. For BCC TMs alloys, the core structure transition from ND to D occurs when χ drops below a threshold, as seen in atomistic simulations based on nearly all extant interatomic potentials and density functional theory (DFT) calculations of W-Re/Ta alloys. In binary W-TMs alloys, DFT calculations show that χ is related to the valence electron concentration at low to moderate solute concentrations, and can be controlled via alloying. χ can be quantitatively and efficiently predicted via rapid, low-cost DFT calculations for any BCC metal alloys, providing a robust, easily applied tool for the design of ductile and tough BCC alloys.

scholarly journals Atomic Resolution Imaging and Quantitative Elemental Mapping of the Misfit Dislocation Core Phase in Multicomponent Oxides

2018 ◽  
Vol 24 (S1) ◽  
pp. 24-25
Author(s):  
N. Bagués ◽  
J. Santiso ◽  
B. D. Esser ◽  
R. E. A. Williams ◽  
D. W. McComb ◽  
...  
Keyword(s):  
Misfit Dislocation ◽  
Dislocation Core ◽  
Atomic Resolution ◽  
Elemental Mapping ◽  
Core Phase ◽  
Resolution Imaging ◽  
Multicomponent Oxides

Atomistic Simulation of Dislocation Motion as Determined by Core Structure

1994 ◽  
Vol 350 ◽  
Author(s):  
Kevin Ternes ◽  
Diana Farkas ◽  
Zhao-Yang Xie
Keyword(s):  
Atomistic Simulation ◽  
Dislocation Core ◽  
Dislocation Motion ◽  
Core Structure ◽  
Planar Structure ◽  
Interatomic Potentials ◽  
Atom Type ◽  
The Core ◽  
Embedded Atom ◽  
Structure And Motion

AbstractTwo different interatomic potentials of the embedded atom type were used to study the relationships between dislocation core structure and mobility. Core structures were computed for a variety of dislocations in B2 NiAl. Several non-planar cores were studied as they reacted to applied stress and moved. The results show that in some cases, the dislocation core transforms to a planar structure before the dislocation glides, whereas in some other cases the core retains the non-planar structure at stresses sufficient to sustain glide. The effects of stoichiometry deviations on the core structure and motion were also studied.

The effect of shear stress on the screw dislocation core structure in body-centred cubic lattices

1973 ◽  
Vol 332 (1588) ◽  
pp. 85-111 ◽  
Keyword(s):  
Shear Stress ◽  
Screw Dislocation ◽  
Plastic Flow ◽  
Stacking Faults ◽  
Dislocation Core ◽  
Stacking Fault ◽  
Core Structure ◽  
Cubic Lattices ◽  
The Core ◽  
Dislocation Core Structure

The behaviour of the ½ a <111> screw dislocation core in the presence of an external shear stress on {110} planes has been studied for a variety of effective interionic potentials, each representing a stable b. c. c. lattice. The distortion and motion of the core are described using the concept of fractional dislocations, which are imperfect dislocations bounding a ribbon of generalized (unstable) stacking fault. Three essentially distinct types of movement are found, and the relation of these to plastic flow and twinning in real b. c. c. metals is discussed. It is found that the movement of the dislocation core can be rationalized in terms of the relative stresses needed to create generalized stacking faults on {110} and {112} planes.

Indexicality of Grammar: The Case of Japanese Transgender Speakers

2019 ◽  
Author(s):  
Hideko Abe
Keyword(s):  
Gender Identity ◽  
Gender Identity Disorder ◽  
Grammatical Gender ◽  
Core Structure ◽  
Subject Positions ◽  
Transgender Identity ◽  
The Core ◽  
History Of ◽  
History Of Scholarship ◽  
Grammatical Structures

This article discusses how the intersection of grammatical gender and social gender, entwined in the core structure of language, can be analyzed to understand the dynamic status of selfhood. After reviewing a history of scholarship that demonstrates this claim, the discussion analyzes the language practices of transgender individuals in Japan, where transgender identity is currently understood in terms of sei-dōitsusei-shōgai (gender identity disorder). Based on fieldwork conducted between 2011 and 2017, the analysis reveals how individuals identifying with sei-dōitsusei-shōgai negotiate subject positions by manipulating the specific indexical meanings attached to grammatical structures.

Solvent-free and efficient synthesis of bicyclic 2-pyridone derivatives for endoplasmic reticulum imaging

2021 ◽  
Author(s):  
Xiaoyun Ran ◽  
Qian Zhou ◽  
Jin Zhang ◽  
Shanqiang Wang ◽  
Gui Wang ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Citric Acid ◽  
Core Structure ◽  
Solvent Free ◽  
Efficient Synthesis ◽  
The Core ◽  
Catalyst Free ◽  
Synthesis Approach ◽  
Ethylenediamine Derivatives

Started from citric acid (CA) and ethylenediamine derivatives, a solvent-free, catalyst-free and highly yield synthesis approach for bicyclic 2-pyridones was presented. Continuing to modify the core structure, a series of...

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