Atomistic simulations and continuum modeling of dislocation nucleation and strength in gold nanowires

Weinberger, Christopher R.; Jennings, Andrew T.; Kang, Keonwook; Greer, Julia R.

doi:10.1016/j.jmps.2011.09.010

Cited by 110 publications

(96 citation statements)

References 60 publications

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“…14,27 In the absence of a pinned dislocation segment, the critical length scale, D, is not necessarily associated with the film thickness. Rather, atomistic and analytical models studying homogeneous nucleation 52 and heterogeneous dislocation nucleation 28,53,54 showed much smaller critical dislocation loops, with the critical radius on the order of a few nanometers. Such a small critical radius further suggests an important contribution from thermal effects.…”

Section: Classical Dislocation Source Modelmentioning

confidence: 95%

“…32 It should be noted that the strengths of these pillars always showed size-dependent strength; however, the effects of a constant displacement rate, as opposed to a constant strain rate, and the relatively few samples tested precludes a definitive conclusion. Further, as the critical dislocation nucleation radius is on the order of a few nanometers, 28,53,54 variations over these small distances such as individual surface steps may play a key role in determining a material's resistance to heterogeneous dislocation nucleation.…”

Section: E Effects Of Imperfections On Dislocation Nucleationmentioning

confidence: 99%

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Heterogeneous dislocation nucleation from surfaces and interfaces as governing plasticity mechanism in nanoscale metals

Jennings

Greer

2011

J. Mater. Res.

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We report the results of constant strain rate experiments on electroplated, single crystalline copper pillars with diameters between 75 and 525 nm. At slow strain rates, 10 À3 s À1, pillar diameters with 150 nm and above show a size-dependent strength similar to previous reports. Below 150 nm, we find that the size effect vanishes as the strength transitions to a relatively size-independent regime. Strain rate sensitivity and activation volume are determined from uniaxial compression tests at different strain rates and corroborate a deformation mechanism change. These results are discussed in the framework of recent in situ transmission electron microscopy experiments observing two distinct deformation mechanisms in pillars and thin films on flexible substrates: partial dislocation nucleation from stress concentrations in smaller structures and single arm source operation in larger samples. Models attempting to explain these different size-dependent regimes are discussed in relation to these experiments and existing literature revealing further insights into the likely small-scale deformation mechanisms.

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Section: Classical Dislocation Source Modelmentioning

confidence: 95%

Section: E Effects Of Imperfections On Dislocation Nucleationmentioning

confidence: 99%

Heterogeneous dislocation nucleation from surfaces and interfaces as governing plasticity mechanism in nanoscale metals

Jennings

Greer

2011

J. Mater. Res.

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“…However, experiments are conducted under constant strain rate. An implicit expression for the strength can be derived from the survival probability of a nanowire under constant strain rate as [51,75,79]…”

Section: Atomistics Simulations Of Dislocation Nucleationmentioning

confidence: 99%

The fundamentals of plastic deformation : several case studies of plasticity in confined volumes.

Weinberger

2012

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Plasticity in small volumes is significantly different than in large, bulk-like specimens. The strength of materials in the micron and sub-micron regime depends not only on the microstructure but also on the size of the material. Given that a number of important mechanical processes occur at these length scales, it is important to build a comprehensive understanding of these materials and processes. This work examines several different processes in small volumes. The motion of dislocations in the drag regime are examined as a function of material volume which exhibits higher drag than in the bulk. The stability of single arm sources are also investigated using molecular dynamics. Finally, dislocation nucleation from the free surface is investigated using both atomistic as well as continuum models. These results provide a better understanding of plastic processes in confined volumes.3 Acknowledgment

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“…In MD simulations thermal activation also can be suppressed because of the high strain rate. Thus, a correspondence may be expected between molecular statics and MD simulations at low temperatures (16)(17)(18). However, the equivalence can break down when the strain rates are so high in MD simulations that the system is driven out of equilibrium.…”

mentioning

confidence: 96%

“…Molecular static calculations, akin to simulations at high strain rate and low temperature (16)(17)(18), showed that an edge dislocation passes through a cluster of self-interstitial atoms (SIAs) under shear deformation, with both defects recovering their original structures after the interaction (1). On the other hand, in postmortem transmission electron microscopy (TEM) on irradiated Zr specimens deformed at low strain rates (10 −4 s −1 ) and high temperature (600 K), a formation of so-called cleared channels was observed.…”

mentioning

confidence: 99%

Mapping strain rate dependence of dislocation-defect interactions by atomistic simulations

Fan¹,

Osetsky

Yip

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Probing the mechanisms of defect-defect interactions at strain rates lower than 10 6 s −1 is an unresolved challenge to date to molecular dynamics (MD) techniques. Here we propose an original atomistic approach based on transition state theory and the concept of a strain-dependent effective activation barrier that is capable of simulating the kinetics of dislocation-defect interactions at virtually any strain rate, exemplified within 10 −7 to 10 7 s −1 . We apply this approach to the problem of an edge dislocation colliding with a cluster of self-interstitial atoms (SIAs) under shear deformation. Using an activation-relaxation algorithm [Kushima A, et al. (2009) J Chem Phys 130:224504], we uncover a unique strain-ratedependent trigger mechanism that allows the SIA cluster to be absorbed during the process, leading to dislocation climb. Guided by this finding, we determine the activation barrier of the trigger mechanism as a function of shear strain, and use that in a coarsegraining rate equation formulation for constructing a mechanism map in the phase space of strain rate and temperature. Our predictions of a crossover from a defect recovery at the low strainrate regime to defect absorption behavior in the high strain-rate regime are validated against our own independent, direct MD simulations at 10 5 to 10 7 s −1 . Implications of the present approach for probing molecular-level mechanisms in strain-rate regimes previously considered inaccessible to atomistic simulations are discussed.structural materials | mechanical properties | low strain rate atomistic simulation

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Atomistic simulations and continuum modeling of dislocation nucleation and strength in gold nanowires

Cited by 110 publications

References 60 publications

Heterogeneous dislocation nucleation from surfaces and interfaces as governing plasticity mechanism in nanoscale metals

Heterogeneous dislocation nucleation from surfaces and interfaces as governing plasticity mechanism in nanoscale metals

The fundamentals of plastic deformation : several case studies of plasticity in confined volumes.

Mapping strain rate dependence of dislocation-defect interactions by atomistic simulations

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