Size Effect in the Shear-Coupled Migration of Grain Boundaries Pinned by Triple Junctions

2009 ◽  
Vol 1224 ◽  
Author(s):  
Javier Gil Sevillano ◽  
Aitor Luque ◽  
Javier Aldazabal ◽  
José Manuel Martinez-Esnaola
Keyword(s):  
Molecular Dynamics ◽  
Simple Model ◽  
Low Temperature ◽  
Size Effect ◽  
Model Structure ◽  
Triple Junctions ◽  
Columnar Grains ◽  
Tilt Boundaries ◽  
Relationship Breakdown ◽  
Dynamics Simulations

AbstractThis paper presents molecular dynamics simulations of shear-coupled migration of tilt boundaries pinned by triple junctions in a simple model structure of columnar grains of different sizes. Simulations are for copper at 300 K. The phenomenon is of interest as a possible explanation of the Hall-Petch relationship breakdown in nano-grained polycrystals deformed at high or moderate strain rate and low-temperature.

Rotation-induced axial oscillation of a composite nanoconvertor at low temperature

2020 ◽  
pp. 107754632093711
Author(s):  
Bo Song ◽  
Kun Cai ◽  
Jiao Shi ◽  
Qing-Hua Qin
Keyword(s):  
Molecular Dynamics ◽  
Low Temperature ◽  
Large Amplitude ◽  
Oscillation Amplitude ◽  
Axial Direction ◽  
Axial Vibration ◽  
Axial Oscillation ◽  
Axial Translation ◽  
Vibration Responses ◽  
Dynamics Simulations

We propose a model of a nanostructure which can transform an input rotation into an output oscillation. In the model, the rotor has two identical internally hydrogenated deformable parts. The mechanism is that the rotation-induced centrifugal force and van der Waals force drive the recoverable deformation of the hydrogenated deformable parts, which gives rise to the axial translation of the free end of the rotor. Once the two hydrogenated deformable parts deform periodically, the free end of the rotor oscillates periodically in the axial direction. Molecular dynamics simulations are conducted to reveal the dynamic response of the system at low temperature. Four main types of deformation and the first three orders of vibration responses of the hydrogenated deformable parts are analyzed. Synchronous breathing vibration of the two hydrogenated deformable parts produces ideal oscillation with large amplitude. Asynchronous axial vibration of the hydrogenated deformable parts reduces the oscillation amplitude or produces beat vibration. The way to control the amplitude of the axial oscillation/vibration is given.

An Atomistic Study of Hydrogen Effects on the Fracture of Tilt Boundaries in Nickel.

1991 ◽  
Vol 238 ◽  
Author(s):  
N. R. Moody ◽  
S. M. Foiles
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Site Occupancy ◽  
Boundary Structure ◽  
Trap Site ◽  
Embedded Atom ◽  
Defect Sites ◽  
Tilt Boundaries ◽  
Temperature Exposure ◽  
Dynamics Simulations

ABSTRACTIn this study, molecular dynamics simulations were used to fracture Σ9 tilt boundaries in nickel lattices containing a range of trap site hydrogen concentrations. These lattices were created in a previous study using Monte Carlo simulations and the Embedded Atom Method to duplicate room temperature exposure to a hydrogen environment. The molecular dynamics simulations were run at absolute zero to immobilize the hydrogen distributions for determination of trap site occupancy effects on grain boundary fracture. In all lattices, fracture began by the breaking of bonds next to polyhedral defect sites that characterize the boundary structure followed by rapid failure of the remaining bonds. The effect of hydrogen was to lower the stress for fracture from 18 GPa to a lower limiting value of 8 GPa as the trap sites along the boundary plane filled. The simulations showed that the atoms at these sites were the only atoms involved in the fracture process. Within the constraints imposed on these calculations, the results of this study showed that the ‘inherent’ effect of hydrogen in the absence of plastic deformation is to reduce the cohesive force between atoms across the boundary.

Effects of Hydrogen on the Fracture Properties of Σ9 and Σ11 Tilt Boundaries in Nickel

1992 ◽  
Vol 278 ◽  
Author(s):  
J.E. Angelo ◽  
W.W. Gerberich ◽  
N.R. Moody ◽  
S.M. Foiles
Keyword(s):  
Molecular Dynamics ◽  
Monte Carlo ◽  
Fracture Stress ◽  
Equilibrium Distribution ◽  
Embedded Atom Method ◽  
Far Field ◽  
Fracture Properties ◽  
Embedded Atom ◽  
Tilt Boundaries ◽  
Dynamics Simulations

AbstractIn this study, the Embedded Atom Method is combined with Monte Carlo and molecular dynamics simulations to study the fracture properties of Σ9 and Σ11 tilt boundaries in nickel. The Monte Carlo simulations are used to simulate the exposure of the bicrystal to a hydrogen environment at 300° C. These simulations establish the equilibrium distribution of hydrogen at the boundaries as a function of far-field concentration. The effect of the hydrogen on the fracture process is then studied with molecular dynamics. It will be shown that the fracture stress of the Σ9 boundary is affected over a wider range of far-field concentrations than the Σ11 boundary, although the Σ11 boundary shows that catastrophic failure occurs when the sample is charged beyond a certain far-field concentration.

Mechanisms of Molecular Beam Epitaxial Growth on Reconstructed Si{100}: Thermal and Energized Beams

1988 ◽  
Vol 141 ◽  
Author(s):  
B. J. Garrison ◽  
M. T. Miller ◽  
D.W. Brenner
Keyword(s):  
Molecular Dynamics ◽  
Low Temperature ◽  
Epitaxial Growth ◽  
Gas Phase ◽  
Molecular Beam ◽  
Energy Deposition ◽  
Amorphous Structure ◽  
Molecular Beam Epitaxial ◽  
Dynamics Simulations ◽  
Molecular Beam Epitaxial Growth

Summary:Molecular dynamics simulations have been performed that examine the microscopic mechanisms of rearrangements of atoms on the Si{ 1001 surface due to deposition of gas phase atoms. For thermal energy deposition we find that the gas atoms initially attach to dangling bonds of the surface dimer atoms. The dimer ’unreconstruction’ is due to a diffusion event on the surface, thus is temperature activated. We also find that dimers may open in regions of the surface where there are several atoms not at lattice sites, thus a low temperature amorphous structure. For 5-10 eV deposition there are direct mechanisms of dimer opening that occur on the 50-100 fs timescale. For energies greater than 15-20 eV there is implantation of the silicon atoms which leads to subsurface damage.

A molecular dynamics investigation on grain disappearance at a triple junction in polycrystalline silicon

2001 ◽  
Vol 677 ◽  
Author(s):  
Alessandra Satta ◽  
Luciano Colombo ◽  
Fabrizio Cleri
Keyword(s):  
Molecular Dynamics ◽  
Triple Junction ◽  
Polycrystalline Silicon ◽  
Critical Radius ◽  
Interatomic Potential ◽  
Atomistic Modeling ◽  
Triple Junctions ◽  
Atomistic Region ◽  
The Stability ◽  
Dynamics Simulations

ABSTRACTTopological changes in microstructure are strictly related to the microscopic evolution of triple junctions (TJ). The three-sided grain disappearance, usually called T2 process, is here investigated via 3D-atomistic modeling. In particular the stability of a three-sided grain insertion in a triple junction in silicon is studied within the framework of Molecular Dynamics simulations. The Stillinger-Weber interatomic potential is adopted and constant-traction border conditions are considered to ensure a proper embedding of the atomistic region in a virtually infinite bulk continuum. Dealing with the T2-event, the critical radius below which the three- sided inner grain become unstable is evaluated to be three to four times the lattice constant of silicon. Moreover, we show that the instability sets in through the amorphization of the central shrinking grain.

Size effect in the melting and freezing behaviors of Al/Ti core-shell nanoparticles using molecular dynamics simulations

2016 ◽  
Vol 25 (3) ◽  
pp. 036102 ◽  
Author(s):  
Jin-Ping Zhang ◽  
Yang-Yang Zhang ◽  
Er-Ping Wang ◽  
Cui-Ming Tang ◽  
Xin-Lu Cheng ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Size Effect ◽  
Molecular Dynamics Simulations ◽  
Core Shell ◽  
Shell Nanoparticles ◽  
Dynamics Simulations ◽  
Core Shell Nanoparticles

LEED observations and molecular dynamics simulations of the low-temperature phases of N2 physisordered on graphite

Vacuum ◽  
1983 ◽  
Vol 33 (10-12) ◽  
pp. 857-858 ◽  
Author(s):  
Renee D Diehl ◽  
SC Fain ◽  
J Talbot ◽  
DJ Tildesley ◽  
WA Steele
Keyword(s):  
Molecular Dynamics ◽  
Low Temperature ◽  
Molecular Dynamics Simulations ◽  
Dynamics Simulations
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