Atomistic Modeling and Simulation of Impurity Atmosphere in Silicon and Edge Dislocation Locking Effects

2004 ◽  
Vol 810 ◽  
Author(s):  
A. Karoui
Keyword(s):  
Edge Dislocation ◽  
Theoretical Study ◽  
Dislocation Core ◽  
Atomic Fraction ◽  
Atomistic Modeling ◽  
Self Energy ◽  
Occupancy Probability ◽  
Effect Model ◽  
Dopant Atoms ◽  
Edge Dislocations

ABSTRACTA theoretical study of edge dislocation locking by impurities in silicon is presented. Three groups of impurities are considered: (i) light atoms O, N, and C., (ii) large atoms Ga, and Ge, and (iii) small dopant atoms B, P, and Al. Based on impurity size effect model, these three groups produce distinct different dislocation locking effects. Atoms from the first group strongly bind with edge dislocations. The O, N, and C atmospheres are similar, with a slightly stronger occupancy probability for O and N in the vicinity of the dislocation core. For the second group, Ge loosely binds to dislocation and resists at most 1/3 of the separation shear stress that the first group can withstand. Germanium has only a small chance to reach the dislocation core. The third impurity group does not resist shear any separation stress from edge dislocations. Moreover, B and P atoms can not be trapped at all by edge dislocations. At a local atomic fraction of 10−4, edge dislocation-impurity binding energy varies from 0.008 eV/Å for P to 1.7 eV/Å for N and 1. 8 eV/Å for O. In addition, using molecular mechanics on system of 34552 atoms the self-energy of an edge dislocation was calculated and found equal to 156 meV/Å.

scholarly journals Incompatible strain gradient elasticity of Mindlin type: screw and edge dislocations

2021 ◽  
Author(s):  
Markus Lazar
Keyword(s):  
Elastic Constants ◽  
Edge Dislocation ◽  
Strain Gradient ◽  
Characteristic Length ◽  
Gradient Elasticity ◽  
Dislocation Core ◽  
Stress Fields ◽  
Cauchy Stress ◽  
Strain Gradient Elasticity ◽  
Edge Dislocations

AbstractThe fundamental problem of dislocations in incompatible isotropic strain gradient elasticity theory of Mindlin type, unsolved for more than half a century, is solved in this work. Incompatible strain gradient elasticity of Mindlin type is the generalization of Mindlin’s compatible strain gradient elasticity including plastic fields providing in this way a proper eigenstrain framework for the study of defects like dislocations. Exact analytical solutions for the displacement fields, elastic distortions, Cauchy stresses, plastic distortions and dislocation densities of screw and edge dislocations are derived. For the numerical analysis of the dislocation fields, elastic constants and gradient elastic constants have been used taken from ab initio DFT calculations. The displacement, elastic distortion, plastic distortion and Cauchy stress fields of screw and edge dislocations are non-singular, finite, and smooth. The dislocation fields of a screw dislocation depend on one characteristic length, whereas the dislocation fields of an edge dislocation depend on up to three characteristic lengths. For a screw dislocation, the dislocation fields obtained in incompatible strain gradient elasticity of Mindlin type agree with the corresponding ones in simplified incompatible strain gradient elasticity. In the case of an edge dislocation, the dislocation fields obtained in incompatible strain gradient elasticity of Mindlin type are depicted more realistic than the corresponding ones in simplified incompatible strain gradient elasticity. Among others, the Cauchy stress of an edge dislocation obtained in incompatible isotropic strain gradient elasticity of Mindlin type looks more physical in the dislocation core region than the Cauchy stress obtained in simplified incompatible strain gradient elasticity and is in good agreement with the stress fields of an edge dislocation computed in atomistic simulations. Moreover, it is shown that the shape of the dislocation core of an edge dislocation has a more realistic asymmetric form due to its inherent asymmetry in incompatible isotropic strain gradient elasticity of Mindlin type than the dislocation core possessing a cylindrical symmetry in simplified incompatible strain gradient elasticity. It is revealed that the considered theory with the incorporation of three characteristic lengths offers a more realistic description of an edge dislocation than the simplified incompatible strain gradient elasticity with only one characteristic length.

Computer Simulation of Creation and Motion of Edge Dislocations in Face Centered Crystals

1994 ◽  
Vol 356 ◽  
Author(s):  
N. Tajima ◽  
T. Nozaki ◽  
T. Hirade ◽  
Y. Kogure ◽  
Masao Doyama
Keyword(s):  
Molecular Dynamics ◽  
Computer Simulation ◽  
Edge Dislocation ◽  
Embedded Atom ◽  
Small Crystals ◽  
Face Centered ◽  
Edge Dislocations

AbstractComplete and dissociated edge dislocations were created near the center of the surface (101) of aluminum small crystals whose surfaces are (111), (111), (101), (101). (121) and (121). Molecular dynamics with N-body embedded atom potentials were used. Higher stress is needed to create a complete edge dislocation than to create a dissociated dislocation.

Basal Plane Dislocation Multiplication via the Hopping Frank-Read Source Mechanism and Observations of Prismatic Glide in 4H-SiC

2012 ◽  
Vol 717-720 ◽  
pp. 327-330 ◽  
Author(s):  
Huan Huan Wang ◽  
Sha Yan Byrapa ◽  
F. Wu ◽  
Balaji Raghothamachar ◽  
Michael Dudley ◽  
...  
Keyword(s):  
Shear Stress ◽  
Slip Plane ◽  
Opposite Direction ◽  
Edge Dislocation ◽  
Basal Plane ◽  
Detailed Mechanism ◽  
Slip Planes ◽  
Basal Plane Dislocation ◽  
Edge Dislocations ◽  
Dislocation Multiplication

In this paper, we report on the synchrotron white beam topographic (SWBXT) observation of “hopping” Frank-Read sources in 4H-SiC. A detailed mechanism for this process is presented which involves threading edge dislocations experiencing a double deflection process involving overgrowth by a macrostep (MP) followed by impingement of that macrostep against a step moving in the opposite direction. These processes enable the single-ended Frank-Read sources created by the pinning of the deflected basal plane dislocation segments at the less mobile threading edge dislocation segments to “hop” from one slip plane to other parallel slip planes. We also report on the nucleation of 1/3< >{ } prismatic dislocation half-loops at the hollow cores of micropipes and their glide under thermal shear stress.

Atomistic Modeling of Extended Defects in Metalic Alloys: Dislocations and Grain Boundaries in Ll2 Compounds

1990 ◽  
Vol 186 ◽  
Author(s):  
V. Vitek ◽  
G. J. Ackland ◽  
J. Cserti
Keyword(s):  
Grain Boundaries ◽  
Dislocation Core ◽  
Extended Defects ◽  
Atomistic Modeling ◽  
Many Body ◽  
Deformation And Fracture ◽  
Governing Factor ◽  
Atomic Interactions ◽  
Total Energies ◽  
Physical Features

AbstractExtended defects, such as dislocations and grain boundaries, control a wide variety of material properties and their atomic structure is often a governing factor. A necessary precursor for modeling of these structures is a suitable description of atomic interactions. We present here empirical many-body potentials for alloys which represent a very simple scheme for the evaluation of total energies and yet reflect correctly the basic physical features of the alloy systems modeled. As examples of atomistic studies we show results of calculations of the core structures of screw dislocations in Ll2 compounds. The same potentials have also been used to calculate structures of grain boundaries in these compounds. The deformation and fracture behavior of Ll2 alloys is then discussed in the light of grain boundary and dislocation core studies.

The Site Preference of Alloying Element Zr in NiAl Dislocation Core and its Effects on Bond Characters

2013 ◽  
Vol 344 ◽  
pp. 19-26
Author(s):  
Li Qun Chen ◽  
Zheng Chen Qiu
Keyword(s):  
Binding Energy ◽  
Edge Dislocation ◽  
Dislocation Core ◽  
Dislocation Motion ◽  
Partial Density ◽  
Site Preference ◽  
Alloying Element ◽  
Dislocation Interaction ◽  
High Temperature Alloys ◽  
Potential Applications

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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