Short-range dislocation interactions using molecular dynamics: Annihilation of screw dislocations

We present results of a large-scale atomistic study of the annihilation of oppositely signed screw dislocations in an fcc metal using molecular dynamics (MD) and an Embedded-Atom-Method (EAM) potential for Cu. The mechanisms of the annihilation process are studied in detail. From the simulation results, we determined the interaction energy between the dislocations as a function of separation. These results are compared with predictions from linear elasticity to examine the onset of non-linear-elastic interactions. The applicability of heuristic models for annihilation of dislocations in large-scale dislocation dynamics simulations is discussed in the light of these results.

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Deformation Behavior of Nanocrystalline Body-Centered Cubic Iron with Segregated, Foreign Interstitial: A Molecular Dynamics Study

Materials ◽

10.3390/ma13235351 ◽

2020 ◽

Vol 13 (23) ◽

pp. 5351

Author(s):

Ahmed Tamer AlMotasem ◽

Matthias Posselt ◽

Tomas Polcar

Keyword(s):

Molecular Dynamics ◽

Grain Boundary ◽

Deformation Behavior ◽

Large Scale ◽

Grain Boundary Sliding ◽

Carbon And Nitrogen ◽

Embedded Atom ◽

Boundary Sliding ◽

Dynamics Simulations

In the present work, modified embedded atom potential and large-scale molecular dynamics’ simulations were used to explore the effect of grain boundary (GB) segregated foreign interstitials on the deformation behavior of nanocrystalline (nc) iron. As a case study, carbon and nitrogen (about 2.5 at.%) were added to (nc) iron. The tensile test results showed that, at the onset of plasticity, grain boundary sliding mediated was dominated, whereas both dislocations and twinning were prevailing deformation mechanisms at high strain. Adding C/N into GBs reduces the free excess volume and consequently increases resistance to GB sliding. In agreement with experiments, the flow stress increased due to the presence of carbon or nitrogen and carbon had the stronger impact. Additionally, the simulation results revealed that GB reduction and suppressing GBs’ dislocation were the primary cause for GB strengthening. Moreover, we also found that the stress required for both intragranular dislocation and twinning nucleation were strongly dependent on the solute type.

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Molecular Dynamics Studies of the Melting of Copper with Vacancies amd Dislocations at High Pressures

MRS Advances ◽

10.1557/adv.2017.353 ◽

2017 ◽

Vol 2 (48) ◽

pp. 2597-2602 ◽

Cited By ~ 1

Author(s):

Clarence C Matthai ◽

Jessica Rainbow

Keyword(s):

Molecular Dynamics ◽

Melting Temperature ◽

Large Scale ◽

High Pressures ◽

Defect Density ◽

Melting Process ◽

Interatomic Potentials ◽

Embedded Atom ◽

Line Defects ◽

Dynamics Simulations

ABSTRACTMolecular dynamics simulations of the melting process of bulk copper were performed using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) with the interatomic potentials being described by the embedded atom method. The aim of the study was to understand the effects of high pressures and defects on the melting temperature. The simulations were visualised using Visual Molecular Dynamics (VMD). The melting temperature of a perfect copper crystal, was found to be slightly higher than the experimentally observed value. The melting temperature as a function of pressure was determined and compared with experiment. Point and line defects, in the form of dislocations, were then introduced into crystal and the new melting temperature of the crystal determined. We find that the melting temperature decreases as the defect density is increased. Additionally, the slope of the melting temperature curve was found to decrease as the pressure was increased while the vacancy formation energy increases with pressure.

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Structure of a Dissociated Edge Dislocation in Copper

MRS Proceedings ◽

10.1557/proc-578-223 ◽

1999 ◽

Vol 578 ◽

Author(s):

L. F. Perondi ◽

P. Szelestey ◽

K. Kaski

Keyword(s):

Molecular Dynamics ◽

Boundary Conditions ◽

Edge Dislocation ◽

Equilibrium Distance ◽

Embedded Atom ◽

Equilibrium Size ◽

Atomic Interactions ◽

Simulated System ◽

Dynamics Simulations ◽

Eam Potential

AbstractThe structure of a dissociated edge dislocation in copper is investigated. Attention is given to the structure of the Shockley partials and the equilibrium size of the fault ribbon. The studies are carried out through Molecular Dynamics simulations. The atomic interactions have been modelled through an Embedded Atom Model (EAM) potential. the implementation of which has been specially designed for this study. Our main results show that the equilibrium distance between partials is very sensitive to the type of boundary conditions imposed on the simulated system.

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Cascade Overlap in hcp Zirconium: Defect Accumulation and Microstructure Evolution with Radiation using Molecular Dynamics Simulations

MRS Proceedings ◽

10.1557/opl.2013.122 ◽

2013 ◽

Vol 1514 ◽

pp. 37-42 ◽

Cited By ~ 1

Author(s):

Prithwish K. Nandi ◽

Jacob Eapen

Keyword(s):

Molecular Dynamics ◽

Molecular Dynamics Simulations ◽

Microstructure Evolution ◽

Stacking Faults ◽

Embedded Atom Method ◽

Shockley Partial Dislocation ◽

Embedded Atom ◽

Defect Accumulation ◽

Dynamics Simulations ◽

Eam Potential

ABSTRACTMolecular dynamics simulations are performed to investigate the defect accumulation and microstructure evolution in hcp zirconium (Zr) – a material which is widely used as clad for nuclear fuel. Cascades are generated with a 3 keV primary knock-on atom (PKA) using an embedded atom method (EAM) potential with interactions modified for distances shorter than 0.1 Å. With sequential cascade simulations we show the emergence of stacking faults both in the basal and prism planes, and a Shockley partial dislocation on the basal plane.

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Strength and Brittleness of Interfaces in Fe-Al Superalloy Nanocomposites under Multiaxial Loading: An ab initio and Atomistic Study

Nanomaterials ◽

10.3390/nano8110873 ◽

2018 ◽

Vol 8 (11) ◽

pp. 873 ◽

Cited By ~ 13

Author(s):

Petr Šesták ◽

Martin Friák ◽

David Holec ◽

Monika Všianská ◽

Mojmír Šob

Keyword(s):

Molecular Dynamics ◽

Tensile Strength ◽

Ab Initio ◽

Molecular Dynamics Simulations ◽

Mechanical Stability ◽

Tensile Tests ◽

Lateral Stress ◽

Dynamics Simulations ◽

Atomistic Study ◽

Eam Potential

We present an ab initio and atomistic study of the stress-strain response and elastic stability of the ordered Fe 3 Al compound with the D0 3 structure and a disordered Fe-Al solid solution with 18.75 at.% Al as well as of a nanocomposite consisting of an equal molar amount of both phases under uniaxial loading along the [001] direction. The tensile tests were performed under complex conditions including the effect of the lateral stress on the tensile strength and temperature effect. By comparing the behavior of individual phases with that of the nanocomposite we find that the disordered Fe-Al phase represents the weakest point of the studied nanocomposite in terms of tensile loading. The cleavage plane of the whole nanocomposite is identical to that identified when loading is applied solely to the disordered Fe-Al phase. It also turns out that the mechanical stability is strongly affected by softening of elastic constants C ′ and/or C 66 and by corresponding elastic instabilities. Interestingly, we found that uniaxial straining of the ordered Fe 3 Al with the D0 3 structure leads almost to hydrostatic loading. Furthermore, increasing lateral stress linearly increases the tensile strength. This was also confirmed by molecular dynamics simulations employing Embedded Atom Method (EAM) potential. The molecular dynamics simulations also revealed that the thermal vibrations significantly decrease the tensile strength.

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NiAl thin film growth on Ni(001) substrate using molecular dynamics simulations

The European Physical Journal Applied Physics ◽

10.1051/epjap/2020200186 ◽

2020 ◽

Vol 91 (3) ◽

pp. 30301

Author(s):

Hicham El Azrak ◽

Abdessamad Hassani ◽

Khalid Sbiaai ◽

Abdellatif Hasnaoui

Keyword(s):

Thin Film ◽

Molecular Dynamics ◽

Molecular Dynamics Simulations ◽

Film Growth ◽

Deposition Process ◽

Thin Film Growth ◽

Embedded Atom ◽

Dynamics Simulations ◽

Eam Potential ◽

Deposited Film

We have studied thin film growth of NiAl on Nickel (001) substrate using molecular dynamics simulations (MD) based on the Embedded Atom Method (EAM) potential. An incidence energy of 0.06 eV at 800 K, 900 K and 1000 K was considered. After the deposition process, we have obtained a B2-NiAl structure film with different percentages; 32.6% for the temperature 1000 K, 30% for 900 K and 25% for 800 K. Our investigation has prompt us to analyze the crystalline structure. During the evolution of deposited film, we observe the formation of grains with different orientation, as well as the appearance of vacancies in Ni and Al sublattices and antisites.

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Network Connectivity in Icosahedra Medium-Range Order of Metallic Mg70Zn30 Alloy

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.727.801 ◽

2017 ◽

Vol 727 ◽

pp. 801-805

Author(s):

Li Li Zhou ◽

Zheng Zhong

Keyword(s):

Molecular Dynamics ◽

Network Connectivity ◽

Physical Nature ◽

Precise Method ◽

Embedded Atom ◽

Extended Range ◽

Medium Range ◽

Dynamics Simulations ◽

Eam Potential ◽

Zn Alloy

The molecular dynamics simulations with embedded atom model (EAM) potential had performed to investigate the icosahedral network connectivity in Mg70Zn30 alloy. The microstructure was detected with a new precise method of largest standard cluster analysis. It was validated that the EAM potential is succeed in reflecting the objective physical nature of Mg-Zn alloy systems. Results shows that large amount of nanoclusters consist of ICOIs, which shows large connectivity variations, formed in the system with decreasing temperature. And the ICOIs connect over extended range act as backbone for a networked structure.

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Massively Parallel Molecular Dynamics Simulations of Two-dimensional Materials at High Strain Rates

MRS Proceedings ◽

10.1557/proc-291-91 ◽

1992 ◽

Vol 291 ◽

Cited By ~ 3

Author(s):

Norman J. Wagner ◽

Brad Lee Holian

Keyword(s):

Molecular Dynamics ◽

Molecular Dynamics Simulations ◽

Large Scale ◽

Spall Strength ◽

Computer Experiments ◽

Dislocation Dynamics ◽

Parallel Computer ◽

Massively Parallel ◽

Connection Machine ◽

Dynamics Simulations

ABSTRACTLarge scale molecular dynamics simulations on a massively parallel computer are performed to investigate the mechanical behavior of 2-dimensional materials. A model embedded atom many- body potential is examined, corresponding to “ductile” materials. A parallel MD algorithm is developed to exploit the architecture of the Connection Machine, enabling simulations of > 106atoms. A model spallation experiment is performed on a 2-D triagonal crystal with a well-defined nanocrystalline defect on the spall plane. The process of spallation is modelled as a uniform adiabatic expansion. The spall strength is shown to be proportional to the logarithm of the applied strain rate and a dislocation dynamics model is used to explain the results. Good predictions for the onset of spallation in the computer experiments is found from the simple model. The nanocrystal defect affects the propagation of the shock front and failure is enhanced along the grain boundary.

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