scholarly journals Surface Effects on the Properties of Screw Dislocation in Nanofilms

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Lili Liu ◽  
Zhenya Meng ◽  
Gang Xu ◽  
Chenglin He ◽  
Xiaozhi Wu ◽  
...  
Keyword(s):  
Screw Dislocation ◽  
Governing Equation ◽  
Surface Effect ◽  
Stacking Fault ◽  
Peierls Stress ◽  
First Principle ◽  
Screw Dislocations ◽  
The Core ◽  
Core Width ◽  
Stacking Fault Energies

The image dislocation method is used to construct the governing equation of dislocations in nanofilms. The classical Peierls-Nabarro equation can be recovered when the thickness of nanofilm is taken to be infinite. In order to determine the core width and Peierls stress of dislocations, the unstable stacking fault energies of Al and Cu nanofilms are calculated via the first-principle methods. It is found that surface effect can increase the Peierls stresses of screw dislocations in Al and Cu nanofilms.

Influence of Ni and N on generalized stacking-fault energies in Fe–Cr–Ni alloy: A first principle study

2012 ◽  
Vol 407 (5) ◽  
pp. 891-895 ◽  
Author(s):  
Jie Liu ◽  
Peide Han ◽  
Minghui Dong ◽  
Guangwei Fan ◽  
Guanjun Qiao ◽  
...  
Keyword(s):  
Stacking Fault ◽  
First Principle ◽  
Ni Alloy ◽  
Generalized Stacking Fault ◽  
Stacking Fault Energies

scholarly journals The Third-Order Elastic Constants and Mechanical Properties of 30° Partial Dislocation in Germanium: A Study from the First-Principles Calculations and the Improved Peierls−Nabarro Model

Crystals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 4
Author(s):  
Huili Zhang ◽  
Defang Lu ◽  
Yu Sun ◽  
Yunchang Fu ◽  
Lumei Tong
Keyword(s):  
Lattice Constant ◽  
Elastic Constants ◽  
First Principles ◽  
Partial Dislocation ◽  
Stacking Fault ◽  
Peierls Stress ◽  
First Principles Calculations ◽  
Third Order ◽  
The Third ◽  
Core Width

The elastic constants, core width and Peierls stress of partial dislocation in germanium has been investigated based on the first-principles calculations and the improved Peierls−Nabarro model. Our results suggest that the predictions of lattice constant and elastic constants given by LDA are in better agreement with experiment results. While the lattice constant is overestimated at about 2.4% and most elastic constants are underestimated at about 20% by the GGA method. Furthermore, when the applied deformation is larger than 2%, the nonlinear elastic effects should be considered. And with the Lagrangian strains up to 8%, taking into account the third-order terms in the energy expansion is sufficient. Except the original γ—surface generally used before (given by the first-principles calculations directly), the effective γ—surface proposed by Kamimura et al. derived from the original one is also used to study the Peierls stress. The research results show that when the intrinsic−stacking−fault energy (ISFE) is very low relative to the unstable−stacking−fault energy (USFE), the difference between the original γ—surface and the effective γ—surface is inapparent and there is nearly no difference between the results of Peierls stresses calculated from these two kinds of γ—surfaces. As a result, the original γ—surface can be directly used to study the core width and Peierls stress when the ratio of ISFE to the USFE is small. Since the negligence of the discrete effect and the contribution of strain energy to the dislocation energy, the Peierls stress given by the classical Peierls−Nabarro model is about one order of magnitude larger than that given by the improved Peierls−Nabarro model. The result of Peierls stress estimated by the improved Peierls−Nabarro model agrees well with the 2~3 GPa reported in the book of Solid State Physics edited by F. Seitz and D. Turnbull.

scholarly journals Effects of Alloying Elements on the Stacking Fault Energies of Ni58Cr32Fe10 Alloys: A First-Principle Study

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1163 ◽  
Author(s):  
Yuchen Dou ◽  
Hong Luo ◽  
Yong Jiang ◽  
Xiaohua Tang
Keyword(s):  
High Performance ◽  
Filler Metal ◽  
Alloy Element ◽  
Stacking Fault ◽  
Alloying Elements ◽  
Filler Materials ◽  
First Principle ◽  
Magnetic Entropy ◽  
Alloy 690 ◽  
Stacking Fault Energies

Ni58Cr32Fe10-based alloys, such as Alloy 690 and filler metal 52 (FM-52), suffer from ductility dip cracking (DDC). It is reported that decreasing the stacking fault energy (SFE) of these materials could improve the DDC resistance of Alloy 690. In this work, the effects of alloying elements on the stacking fault energies (SFEs) of Ni58Cr32Fe10 alloys were studied using first-principle calculations. In our simulations, 2 at.% of Ni is replaced by alloy element X (X=Al, Co, Cu, Hf, Mn, Nb, Ta, Ti, V, and W). At a finite temperature, the SFEs were divided into the magnetic entropy (SFEmag) and 0 K (SFE0) contributions. Potentially, the calculated results could be used in the design of high-performance Ni58Cr32Fe10-based alloys or filler materials.

On the core width and Peierls stress of bubble rafts dislocations within the framework of modified Peierls-Nabarro model

Open Physics ◽  
2011 ◽  
Vol 9 (4) ◽  
Author(s):  
Xiaozhi Wu ◽  
Lili Liu ◽  
Rui Wang ◽  
Na Ji
Keyword(s):  
Strain Energy ◽  
Bubble Radius ◽  
Elastic Strain Energy ◽  
Core Structure ◽  
Peierls Stress ◽  
Restoring Force ◽  
The Core ◽  
Core Width ◽  
Lattice Effect ◽  
Discrete Effect

AbstractUsing Foreman’s method, the core structure and Peierls stress of dislocations in bubble rafts have been investigated within the framework of the modified Peierls-Nabarro (P-N) model in which the discrete lattice effect is taken into account. The core width obtained from the modified P-N model is much wider than that from the P-N model owing to the discrete lattice effect. It is found that the core width of dislocation increases with a decrease of the bubble radius. The elastic strain energy associated with the discrete effect is considered while calculating the Peierls stress. The new expression of the Peierls stress obtained in this paper is not explicitly dependent on the particular form of the restoring force law, which is only related to the core structure parameter and can be used expediently to predict the Peierls stress of dislocations. The Peierls stress decreases rapidly with the decrease of the bubble radius.

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 The Properties of Shuffle Screw Dislocations in Semiconductors Silicon and Germanium

2015 ◽  
Vol 9 (1) ◽  
pp. 10-13 ◽  
Author(s):  
Huili Zhang ◽  
Chun Zhang ◽  
Chunhua Zeng ◽  
Lumei Tong
Keyword(s):  
Screw Dislocation ◽  
Peierls Stress ◽  
Diamond Structure ◽  
Screw Dislocations ◽  
Burgers Vector ◽  
Peierls Barrier ◽  
Silicon And Germanium

The dislocation widths, Peierls barriers and Peierls stresses for shuffle screw dislocations in diamond structure crystals, Si and Ge, have been calculated by the improved P-N theory. The widths are about 0.6b, where b is the Burgers vector. The Peierls barrier for shuffle screw dislocation in Si and Ge, is about 3.61~4.61meV/Å and 5.31~13.32meV/Å, respectively. The Peierls stress is about 0.28~0.33GPa and 0.31~0.53GPa, respectively. The calculated Peierls barriers and stresses are likely the results of shuffle screw dislocation with metastable core which is centered on the bond between two atoms.

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.

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