The site preference of refractory element W in NiAl dislocation core and its effects on bond characters

NiAl is one kind of high-temperature alloys with broad potential applications in aerospace industry. Its mechanical properties are believed to be largely related to the dislocation behavior and impurity-dislocation interaction. In the paper we report first principles study of the alloying effect of Zr in the [10(010) edge dislocation core of NiAl. The binding energy of doping system decreases 3.77 eV when a Zr atom substituted for an Al, only decreases 1.06 eV with substitution for a Ni atom. The result of the binding energy shows that a Zr atom prefers to occupy an Al site in the dislocation core of NiAl. The analyses of the charge distribution, the interatomic energy and the partial density of states suggest that Zr will greatly enhance the interaction between Zr atom and neighboring host atoms, as well as that between host atoms. These results show that the alloying element Zr induced pinning effect on the edge dislocation motion is predicted, and could be helpful for understanding microscopic mechanisms of alloying-induce hardening in NiAl alloy.

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Direct structure images of 30° partial dislocation cores in silicon

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100126111 ◽

1987 ◽

Vol 45 ◽

pp. 242-243

Author(s):

J. C. Barry ◽

H. Alexander

Keyword(s):

Dislocation Core ◽

Preparation Technique ◽

Burgers Vector ◽

Vector Type ◽

Sample Preparation Technique ◽

Lattice Images ◽

Dislocation Core Structure ◽

Type Lattice ◽

Direct Inspection

Dislocations in silicon produced by plastic deformation are generally dissociated into partials. 60° dislocations (Burgers vector type 1/2[101]) are dissociated into 30°(Burgers vector type 1/6[211]) and 90°(Burgers vector type 1/6[112]) dislocations. The 30° partials may be either of “glide” or “shuffle” type. Lattice images of the 30° dislocation have been obtained with a JEM 100B, and with a JEM 200Cx. In the aforementioned experiments a reasonable but imperfect match was obtained with calculated images for the “glide” model. In the present experiment direct structure images of 30° dislocation cores have been obtained with a JEOL 4000EX. It is possible to deduce the 30° dislocation core structure by direct inspection of the images. Dislocations were produced by compression of single crystal Si (sample preparation technique described in Alexander et al.).

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Structural analysis of a Σ5 grain boundary in YBa2Cu3O7δ

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010015054x ◽

1993 ◽

Vol 51 ◽

pp. 942-943

Author(s):

J.-Y. Wang ◽

Y. Zhu ◽

A.H. King ◽

M. Suenaga

Keyword(s):

Grain Boundary ◽

Lattice Mismatch ◽

Weak Link ◽

Coincidence Site Lattice ◽

Large Angle ◽

Dislocation Core ◽

Superconducting Order Parameter ◽

Outstanding Problem ◽

Transmission Electron

One outstanding problem in YBa2Cu3O7−δ superconductors is the weak link behavior of grain boundaries, especially boundaries with a large-angle misorientation. Increasing evidence shows that lattice mismatch at the boundaries contributes to variations in oxygen and cation concentrations at the boundaries, while the strain field surrounding a dislocation core at the boundary suppresses the superconducting order parameter. Thus, understanding the structure of the grain boundary and the grain boundary dislocations (which describe the topology of the boundary) is essential in elucidating the superconducting characteristics of boundaries. Here, we discuss our study of the structure of a Σ5 grain boundary by transmission electron microscopy. The characterization of the structure of the boundary was based on the coincidence site lattice (CSL) model.Fig.l shows two-beam images of the grain boundary near the projection. An array of grain boundary dislocations, with spacings of about 30nm, is clearly visible in Fig. 1(a), but invisible in Fig. 1(b).

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ELECTRICAL TRANSPORT IN THE DISLOCATION CORE

Le Journal de Physique Colloques ◽

10.1051/jphyscol:1983413 ◽

1983 ◽

Vol 44 (C4) ◽

pp. C4-113-C4-113

Author(s):

R. Labusch

Keyword(s):

Electrical Transport ◽

Dislocation Core

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Experimental Determination of Dislocation Core Structures by HRTEM

10.21236/ada388647 ◽

2001 ◽

Author(s):

Kevin J. Hemker ◽

Mingwei Chen

Keyword(s):

Experimental Determination ◽

Dislocation Core

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Site preference and atomic ordering in the ternary Rh5Ga2As: first-principles calculations

Zeitschrift für Kristallographie - Crystalline Materials ◽

10.1515/zkri-2021-2019 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Nilanjan Roy ◽

Sucharita Giri ◽

Harshit ◽

Partha P. Jana

Keyword(s):

Total Energy ◽

First Principles ◽

Density Functional ◽

Structure Type ◽

Site Preference ◽

X Ray Diffraction ◽

Atomic Ordering ◽

Functional Theory ◽

The Stability ◽

Bonding Characteristics

Abstract The site preference and atomic ordering of the ternary Rh5Ga2As have been investigated using first-principles density functional theory (DFT). An interesting atomic ordering of two neighboring elements Ga and As reported in the structure of Rh5Ga2As by X-ray diffraction data only is confirmed by first-principles total-energy calculations. The previously reported experimental model with Ga/As ordering is indeed the most stable in the structure of Rh5Ga2As. The calculation detected that there is an obvious trend concerning the influence of the heteroatomic Rh–Ga/As contacts on the calculated total energy. Interestingly, the orderly distribution of As and Ga that is found in the binary GaAs (Zinc-blende structure type), retained to ternary Rh5Ga2As. The density of states (DOS) and Crystal Orbital Hamiltonian Population (COHP) are calculated to enlighten the stability and bonding characteristics in the structure of Rh5Ga2As. The bonding analysis also confirms that Rh–Ga/As short contacts are the major driving force towards the overall stability of the compound.

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