Generalized stacking fault energies for embedded atom FCC metals

Zimmerman, Jonathan A.; Gao, Huajian; Abraham, Farid F.

doi:10.1088/0965-0393/8/2/302

Cited by 290 publications

(156 citation statements)

References 37 publications

(57 reference statements)

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“…Indeed, it is known that EAM Al potentials do not accurately model the unstable stacking fault energy, while DFT is offered as a better approach. 22 While the shear response of the OFDFT compares well to that obtained with a Kohn-Sham DFT formulation with similar parameters and the same local pseudopotential, Fig. 1, the results differ significantly from those obtained with the EAM.…”

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confidence: 51%

Density-functional-theory-based local quasicontinuum method: Prediction of dislocation nucleation

et al. 2004

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We introduce the density functional theory (DFT) local quasicontinuum method: a first principles multiscale material model that embeds DFT unit cells at the subgrid level of a finite element computation. The method can predict the onset of dislocation nucleation in both single crystals and those with inclusions, although extension to lattice defects awaits new methods. We show that the use of DFT versus embedded-atom method empirical potentials results in different predictions of dislocation nucleation in nanoindented face-centered-cubic aluminum. In this paper we establish the feasibility of embedding density functional theory (DFT) into large-scale macroscopic finite-element calculations. The embedding takes place at the subgrid level and exploits the Cauchy-Born hypothesis, 1 whereby the local deformation computed at a quadrature point of the finite-element grid is applied to an infinite crystal lattice, whose energy and state of stress is then evaluated with DFT. We call our method DFT-LQC in reference to the local quasicontinuum (LQC) or Cauchy-Born approach, 2 in anticipation of a future nonlocal extension of the method.The impetus for multiscale descriptions of materials such as DFT-LQC derives from two main sources. From a topdown viewpoint, empirical constitutive models which remain reliable under extreme conditions of pressure, deformation, and deformation rate are often not available for use in largescale engineering simulations. Alternately, it is often desirable to extend the applicability of fundamental theories to engineering spatial and temporal scales. Methods such as DFT-LQC meet these demands by supplying a fundamental description of the material and embedding this description into large-scale engineering simulations.The LQC method, including extensions dealing with complex lattices, has been extensively used by Tadmor et al.,3,4 who used the method to study the nanoindentation of silicon and to analyze the process of polarization switching in PbTiO 3 . Tadmor et al. based their subgrid atomistic calculations on empirical potentials or effective Hamiltonians fitted to first principles calculations.The chief contribution of the present work is to establish the feasibility of using DFT, as opposed to empirical or effective interatomic potentials, as the fundamental description of materials such as aluminum in LQC calculations. Since DFT is a first-principles theory (see Ref. 5, and references therein for background), it may be expected to result in increased fidelity of the calculations, especially when the material is subject to an environment where the empirical potentials were not calibrated. A case in point is provided by nanoindentation, which induces high pressures and deformations under the indenter, even in the elastic range. Indeed, we show that the use of DFT versus embedded-atom method (EAM) empirical potentials results in vastly different predictions of dislocation nucleation in nanoindented facecentered-cubic (fcc) aluminum.The general DFT-LQC method consists of embedding DFT calcul...

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confidence: 51%

Density-functional-theory-based local quasicontinuum method: Prediction of dislocation nucleation

et al. 2004

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“…Despite the considerable volume of interest that this problem has generated, as yet there does not seem to be a common view as to the underlying mechanism behind the defect generation. Several models around the year 1930 were proposed in perfect crystals to estimate the maximum stress before inducing plasticity [1,2]. At the atomic level, the plasticity is described by the rearrangement of atoms from its current configuration.…”

Section: Introductionmentioning

confidence: 99%

Elastic-Plastic Transition under Uniaxial Stress BCC Tantalum

Guerrero¹,

Marucho²

2013

JMSE-B

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Classical molecular dynamics and lattice dynamics were utilized to study the elastic-plastic transition underuniaxial stress in defect free body center cubic (BCC) Tantalum crystals. We demonstrate that the nucleation of defects at the time scales of molecular dynamics in tantalum is due to dynamical instabilities (soft-phonons). Uniaxial compressions test were simulated along the crystallographic directions (100), (110) and (111). The results show that the nucleation of defeccts in the direction (110) is due to crystal twinning.

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“…An important indicator of this is that the generalized stacking fault energy-one of the most important properties for dislocation nucleation-is the same for the LJ potential and more advanced potentials for nickel and copper. 13 We compare the results of planar-extension boundary conditions and boundary conditions based on the K I -continuum solution.…”

Section: Introductionmentioning

confidence: 99%

Molecular dynamics study of dislocation nucleation from a crack tip

Hess¹,

Giessen²,

Thijsse³

2005

Phys. Rev. B

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We have performed a systematic molecular dynamics study of the competition between crack growth and dislocation emission from a crack tip. Two types of boundary conditions are adopted: either planar extension or boundary displacements according to the anisotropic mode-I asymptotic continuum solution. The effects of temperature, loading rate, crystal orientation, sharpness of the crack tip, atomic potential, and system size are investigated. Depending on the crystal orientation, dislocation nucleation can be driven either by the strain or by concerted fluctuations at the crack tip. In the latter case, crystal orientation and temperature have the largest influence on the process of dislocation nucleation.

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Generalized stacking fault energies for embedded atom FCC metals

Cited by 290 publications

References 37 publications

Density-functional-theory-based local quasicontinuum method: Prediction of dislocation nucleation

Density-functional-theory-based local quasicontinuum method: Prediction of dislocation nucleation

Elastic-Plastic Transition under Uniaxial Stress BCC Tantalum

Molecular dynamics study of dislocation nucleation from a crack tip

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