PyCAC: The concurrent atomistic-continuum simulation environment

Xu, Shuozhi; Payne, Thomas G.; Chen, Hao; Liu, Yongchao; Xiong, Liming; Chen, Youping; McDowell, David L.

doi:10.1557/jmr.2018.8

Cited by 39 publications

(16 citation statements)

References 72 publications

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“…For monoatomic face-centred cubic (FCC) crystals, three options are shown in figure 2 with each containing only one atom and having the same volume. They are (a) the Wigner-Seitz cell which is the primitive unit cell widely used in solid-state physics, (b) the rhombohedral shaped unit cell which is the primitive unit cell primarily used in the concurrent atomistic-continuum (CAC) method for modelling of FCC crystals [55][56][57][58][59][60][61][62][63] and the rectangular prism which is the only unit cell for FCC crystals whose faces are mutually orthogonal. Recall that the stress tensor defined by Cauchy is the 'the force per unit area on three given rectangular planes' [19].…”

Section: Numerical Methods For Local Stress Calculationmentioning

confidence: 99%

Asymmetry of the atomic-level stress tensor in homogeneous and inhomogeneous materials

Díaz

et al. 2018

Proc. R. Soc. A.

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The stress tensor is described as a symmetric tensor in all classical continuum mechanics theories and in most existing statistical mechanics formulations. In this work, we examine the theoretical origins of the symmetry of the stress tensor and identify the assumptions and misinterpretations that lead to its symmetric property. We then make a direct measurement of the stress tensor in molecular dynamics simulations of four different material systems using the physical definition of stress as force per unit area acting on surface elements. Simulation results demonstrate that the stress tensor is asymmetric near dislocation cores, phase boundaries, holes and even in homogeneous material under a shear loading. In addition, the atomic virial stress and Hardy stress formulae are shown to significantly underestimate the stress tensor in regions of stress concentration.

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Section: Numerical Methods For Local Stress Calculationmentioning

confidence: 99%

Asymmetry of the atomic-level stress tensor in homogeneous and inhomogeneous materials

Díaz

et al. 2018

Proc. R. Soc. A.

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“…These forces are then used to update the accelerations, velocities, and eventually positions of nodes and atoms. [45,46] As a result, the aforementioned reduction in the number of DOFs (96.47%) is directly related to the computational gain of the CAC simulations with respect to MD. To validate the CAC method and the interatomic potential, we build a Si/Ge (001) semicoherent interface in CAC and compare it, in Figure 2, against a transmission electron microscopy (TEM) image.…”

Section: Methodsmentioning

confidence: 99%

Si/Ge (111) Semicoherent Interfaces: Responses to an In‐Plane Shear and Interactions with Lattice Dislocations

Chen

2020

Physica Status Solidi (b)

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Concurrent atomistic–continuum simulations are employed to study Si/Ge (111) semicoherent interfaces in terms of their responses to an in‐plane shear and interactions with lattice dislocations. Three types of Si/Ge interfaces, differing in interfacial structures and energy, are considered. Type I interface coincides with the shuffle‐set slip plane and contains a hexagonal network of edge dislocations. Type II and Type III interfaces both coincide with the glide‐set slip plane, yet they contain, respectively, a triangular and a hexagonal network of Shockley partial dislocations. The simulations show that among the three types of interfaces, 1) Type I interface is the least stable subject to an in‐plane shear and 2) Type III interface impedes the gliding of lattice dislocations the most significantly.

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“…It follows that homogeneous compressive engineering strain with a constant rate of 10 9 s −1 and time step of 5 fs is applied along the axial z direction. All CAC simulations are carried out using PyCAC (Xu, 2017;Xu et al, 2018b). Atomistic structures are visualized in OVITO (Stukowski, 2010) with lattice defects identified by the centrosymmetry parameter (CSP) (Kelchner et al, 1998).…”

Section: Figmentioning

confidence: 99%

Modeling Plastic Deformation of Nano/Submicron-Sized Tungsten Pillars Under Compression: A Coarse-Grained Atomistic Approach

2018

Int J Mult Comp Eng

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In this work, coarse-grained atomistic simulations via the concurrent atomistic-continuum (CAC) method are performed to investigate compressive deformation of nano-/submicron-sized pillars in body-centered cubic (BCC) tungsten. Two models with different surface roughness are considered. All pillars have the same height-to-diameter aspect ratio of 3, with the diameter ranging from 27.35 to 165.34 nm; as a result, the largest simulation cell contains 291,488 finite elements, compared to otherwise ≈ 687.82 million atoms in an equivalent full atomistic model. Results show that (i) a larger surface roughness leads to a lower yield stress and (ii) the yield stress of pillars with a large surface roughness scales nearly linearly with the diameter while that of pillars with smooth surfaces scales exponentially with the diameter, the latter of which agrees with experiments. The differences in the yield stress between the two models are attributed to their different plastic deformation mechanisms: in the case of large surface roughness, dislocation nucleation is largely localized near the ends of the pillars; and in pillars with smooth surfaces, dislocation avalanches in a more homogeneous manner are observed. This work, which is the first attempt to simulate BCC systems using the CAC method, highlights the significance of the surface roughness in uniaxial deformation of nano-/submicropillars.

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PyCAC: The concurrent atomistic-continuum simulation environment

Abstract: Abstract

Cited by 39 publications

References 72 publications

Asymmetry of the atomic-level stress tensor in homogeneous and inhomogeneous materials

Asymmetry of the atomic-level stress tensor in homogeneous and inhomogeneous materials

Si/Ge (111) Semicoherent Interfaces: Responses to an In‐Plane Shear and Interactions with Lattice Dislocations

Modeling Plastic Deformation of Nano/Submicron-Sized Tungsten Pillars Under Compression: A Coarse-Grained Atomistic Approach

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