Interatomic potentials for monoatomic metals from experimental data and<i>ab initio</i>calculations

Mishin, Y.; Farkas, Diana; Mehl, Michael J.; Papaconstantopoulos, D. A.

doi:10.1103/physrevb.59.3393

Cited by 1,344 publications

(649 citation statements)

References 45 publications

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confidence: 99%

“…The aspect ratio was fixed at 3:1. An embedded-atom method potential for Ni as described by Mishin et al [20] was chosen in the present work because it is calibrated according to ab initio values of stacking fault and twin formation energies [20]. After the initial construction, energy minimization using the conjugate gradient method was performed to obtain the equilibrium configurations.…”

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Alternating starvation of dislocations during plastic yielding in metallic nanowires

2008

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Using molecular dynamics simulations, we show that the mechanical deformation behaviors of single-crystalline nickel nanowires are quite different from their bulk counterparts. Correlation between the obtained stress-strain curves and the visualized defect evolution during deformation processes clearly demonstrates that a sequence of complex dislocation slip events results in a state of dislocation starvation, involving the nucleation and propagation of dislocations until they finally escape from the wires, so that the wires deform elastically until new dislocations are generated. Ó 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Due to the unique mechanical, thermal, electrical and optical properties, materials with nanometer-sized structure have attracted a great deal of interest as potential building blocks in nanoelectronic and nanoelectromechanical devices [1]. Many researchers have demonstrated, through both experiments and analysis, that the structure and properties of nanowires can be quite different from those of bulk materials due to the effect of the large surface to volume ratio [2][3][4][5][6][7][8][9][10][11][12][13][14].Recently, Uchic et al. [15,16] and Greer et al. [17,18] reported that the plastic deformation behavior of single-crystalline sub-micropillars is dependent on the size of the pillar, even without a deformation gradient. More recently, a ''mechanical annealing" test was used to demonstrate that dislocations can be swept out of the samples through the progressive activation and exhaustion of dislocation sources [19]. These promising results raise an important question: is the size effect still operative when the size of the pillar is reduced to under 10 nanometers?Despite many efforts [6][7][8][9][10][11][12][13][14], a quantitative understanding of dislocation flow in nanoscale metals has remained elusive. In particular, the correlation of the dislocation flow with the stress-strain curve is of great interest, for the underlying mechanisms are typically represented by a mechanical response in macroscopic level experiments. An understanding of the post-yielding deformation mechanism is also of paramount importance. However, previous simulations have concentrated on the initial yielding behavior of metallic nanowires [9][10][11], while studies on the post-yielding are still lacking.It is well-known that most conventional bulk metals only have their initial yield point represented by the stress-strain curve, their plastic flow being characterized as continuous dislocation movement after yielding. Here we show, by using molecular dynamics simulations, that metallic nanowires behave in an alternating dislocation starvation manner upon uniaxial compressive loading, which involves dislocation nucleation from free surfaces, dislocation travel across to the opposite side and then escape out of the wire system, so that continued elastic deformation is required to nucleate new dislocations.We focus mainly on Ni[1 1 1] nanowires with a nearly square cross-section. Nanow...

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Alternating starvation of dislocations during plastic yielding in metallic nanowires

2008

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“…The atomistic domain is simulated using MD, where the interatomic forces are represented by an atomistic potential suitably fitted to reproduce the material properties of aluminum [12]. The continuum domain is simulated by using the finite element method (FEM) with anisotropic elastic properties derived from the aluminum potential [12] at room temperature (300K). The coupling between FEM and MD is achieved by the recently-developed embedded statistical coupling method (ESCM) [13,14] to provide elastic boundary conditions for the atomistic domain and transfer the applied far field mechanical load into the atomistic system.…”

Section: The Simulation Approachmentioning

confidence: 99%

Multiscale modeling of intergranular fracture in aluminum: constitutive relation for interface debonding

2008

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Intergranular fracture is a dominant mode of failure in ultrafine grained materials. In the present study, the atomistic mechanisms of grain-boundary debonding during intergranular fracture in aluminum are modeled using a coupled molecular dynamics -finite element simulation. Using a statistical mechanics approach, a cohesive-zone law in the form of a traction-displacement constitutive relationship, characterizing the load transfer across the plane of a growing edge crack, is extracted from atomistic simulations and then recast in a form suitable for inclusion within a continuum finite element model. The cohesive-zone law derived by the presented technique is free of finite size effects and is statistically representative for describing the interfacial debonding of a grain boundary (GB) interface examined at atomic length scales. By incorporating the cohesive-zone law in cohesive-zone finite elements, the debonding of a GB interface can be simulated in a coupled continuum-atomistic model, in which a crack starts in the continuum environment, smoothly penetrates the continuum-atomistic interface, and continues its propagation in the atomistic environment. This study is a step towards relating atomistically derived decohesion laws to macroscopic predictions of fracture and constructing multiscale models for nanocrystalline and ultrafine grained materials.

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“…To keep these surfaces flat, the y-coordinates of some atomic planes adjacent to these surfaces were fixed. The embedded atom method (EAM) developed by Mishin et al [27] was used in this study. This potential has been extensively used in many MD studies of aluminum [28][29][30] for it describes aluminum elastic properties and dislocations in aluminum well [29,31].…”

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Temperature dependence of the yield strength of aluminum thin films: Multiscale modeling approach

Davoudi

2017

Scripta Materialia

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Modeling deformation at elevated temperatures using discrete dislocation dynamics (DDD) is a recent area of high interest. However, the literature dedicated to this subject fails to address the variations of DDD parameters with temperature. This study aims to investigate the effect of temperature on the yield strength of aluminum thin films in two-dimensional DDD simulations. To this end, the temperature dependence of DDD parameters has been studied using molecular dynamics, three-dimensional DDD simulations, and the existing experimental results. Based on these calculations, we observed 18% decrease in the yield strength when temperature was increased from 100 K to 600 K. Discrete dislocation dynamics (DDD) is a powerful tool that has been successfully applied to simulate plastic deformation in crystalline materials specially at the micron and submicron scales in various modeling problems. In this method, the material is modeled as a continuous medium containing dislocations as the main plastic carriers, where evolution of dislocations is tracked. In the formulation of the DDD approach, it is assumed that the motion of a dislocation of unit length is governed by:where v is the dislocation velocity, m * is the effective mass, B is the drag coefficient, and F(t) is the driving force arising from externally applied stresses, image stresses, self-stress, interactions with other defects, and the lattice friction (Peierls stress). In this method, long range interactions between dislocations are calculated through theory of elasticity; short range interactions are determined based on local rules.DDD is implemented either in two-or three-dimensional frameworks. Three-dimensional DDD (3d DDD) includes dislocations in realistic geometries and many dislocation phenomena such as junction formation and cross-slip. 2d simulations include only infinitely long edge dislocations.In 2d approach, Frank-Read (FR) sources are represented by points; when the resolved shear stress exceeds a prescribed nucleation stress during a period of time, called nucleation time, the *

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Interatomic potentials for monoatomic metals from experimental data andab initiocalculations

Cited by 1,344 publications

References 45 publications

Alternating starvation of dislocations during plastic yielding in metallic nanowires

Alternating starvation of dislocations during plastic yielding in metallic nanowires

Multiscale modeling of intergranular fracture in aluminum: constitutive relation for interface debonding

Temperature dependence of the yield strength of aluminum thin films: Multiscale modeling approach

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