Study of the Mechanical Behavior of BCC Transition Metals Using Bond-Order Potentials

Mrovec, Matous; Vítek, V.; Nguyen-Manh, D.; Pettifor, D. G.; Wang, L. G.; Šob, Mojmı́r

doi:10.1557/proc-578-199

Cited by 5 publications

(3 citation statements)

References 30 publications

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“…Hence, they do not capture any directionality of the bonding in BCC materials. More sophisticated potentials have been proposed to account for directional bonding in BCC materials; for example, modified generalized pseudo-potential theory or MGPT in [34,35], angular-dependent interatomic potential orADP in [36], modified embedded atom method or MEAM in [37] and the bond-order potentials or BOP in [38]. However, the computational cost for these potentials is much higher than that for those without directionality, which restricts application to smaller molecular systems.…”

Section: Interatomic Potential For MD Simulationsmentioning

confidence: 99%

Evaluating the effects of loading parameters on single-crystal slip in tantalum using molecular mechanics

Alleman

Ghosh

Luscher

et al. 2013

Philosophical Magazine

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This study is aimed at developing a physics-based crystal plasticity finite element model for body-centred cubic (BCC) metals, through the introduction of atomiclevel deformation information from molecular dynamics (MD) investigations of dislocation motion at the onset of plastic flow. In this study, three critical variables governing crystal plasticity mediated by dislocation motion are considered. MD simulations are first performed across a range of finite temperatures up to 600K to quantify the temperature dependence of critical stress required for slip initiation. An important feature of slip in BCC metals is that it is not solely dependent on the Schmid law measure of resolved shear stress, commonly employed in crystal plasticity models. The configuration of a screw dislocation and its subsequent motion is studied under different load orientations to quantify these non-Schmid effects. Finally, the influence of strain rates on thermal activation is studied by inducing higher stresses during activation at higher applied strain rates. Functional dependence of the critical resolved shear stress on temperature, loading orientation and strain rate is determined from the MD simulation results. The functional forms are derived from the thermal activation mechanisms that govern the plastic behaviour and quantification of relevant deformation variables. The resulting physics-based rate-dependent crystal plasticity model is implemented in a crystal plasticity finite element code. Uniaxial simulations reveal orientation-dependent tension-compression asymmetry of yield that more accurately represents singlecrystal experimental results than standard models.

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Section: Interatomic Potential For MD Simulationsmentioning

confidence: 99%

Evaluating the effects of loading parameters on single-crystal slip in tantalum using molecular mechanics

Alleman

Ghosh

Luscher

et al. 2013

Philosophical Magazine

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show abstract

“…On the other hand, Fig. 1b shows the core structure obtained in calculations employing the recently developed screened bond-order potentials for molybdenum [43][44][45]. The most important feature of these potentials, which are based on the tight-binding approach [42,55,56], is that they reflect the most significant quantum mechanical aspect of bonding in transition metals, formation of directional bonds due to the unfilled d-band.…”

Section: Atomistic Simulations Of Screw Dislocations In Molybdenummentioning

confidence: 99%

“…We concentrate here on molybdenum for which such study was made using central-force many-body potentials [38], potentials based on a modified generalized pseudopotential theory (MGPT) [39][40][41], screened bond-order potentials [42][43][44][45] as well as an ab initio pseudopotential plane-wave method within the local-density approximation of the density functional theory [46,47]. While the details of the core structure are not the same in these calculations the calculated dependence of the CRSS on the orientation of the MRSSP is very similar in all cases.…”

Section: Introductionmentioning

confidence: 99%

Influence of non-glide stresses on plastic flow: from atomistic to continuum modeling

Vítek

Mrovec

Bassani

2004

Materials Science and Engineering: A

120

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The Schmid law, which is accurate for face-centered-cubic (fcc) metals, assumes that only the shear stress acting in the slip plane in the slip direction controls the plastic deformation. Hence, it is implicitly assumed that the critical resolved shear stress (CRSS) for the slip is not affected by any other components of the applied stress tensor. This rule is almost ubiquitously utilized in large-scale continuum computations of plastically deforming single and polycrystals. On the other hand, in materials with more complex structures and for some orientations of the dislocation line the cores can spread onto several non-parallel planes. The most widely-known example is the screw dislocation in bcc metals, though this phenomenon is quite universal in structures that are not close packed. Signatures of such core configurations commonly include unexpected deformation modes and slip geometries, strong and unusual dependence of flow stresses on temperature and strain rate, a high Peierls stress, and, in general, a breakdown of the Schmid law. In this paper, we first summarize results of atomistic computer simulations of the response of 1/2 1 1 1 screw dislocations to the applied shear stresses. The calculations have been made using central-force many-body potentials and tight-binding based bond-order potentials for molybdenum. While the core structure found is not the same for the two descriptions of atomic interactions, both lead to a very similar orientation dependence of the critical resolved shear stress for the dislocation motion which takes place along the most highly stressed {1 1 0} plane. This dependence reveals the break down of the Schmid law invoked by the effect of shear stresses acting in another {1 1 0} plane, which are called non-glide stresses. These results are then transferred to macroscopic level by formulating single crystal yield criteria that include the effects of non-glide components of the stress tensor. These criteria form a basis for multislip yield criteria and flow relations for continuum analyses. Using this approach we demonstrate that the effects of non-glide stresses that have their origin at the level of individual dislocations also have significant effect on polycrystalline response, including a significant tension-compression asymmetry.

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Higher-energy Structures and Stability of Cu and Al Crystals Along Displacive Transformation Paths

Černý

Boyer

Šob

et al. 2006

J Computer-Aided Mater Des

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Stability of ground-state and higher-energy phases of Cu and Al encountered along the tetragonal (bcc-fcc), trigonal (bcc-simple cubic-fcc) and hexagonal (bcc-hcp) displacive transformation paths is studied by ab initio electronic structure calculations (ultra-soft pseudopotentials, VASP code) and by many-body semi-empirical interatomic potentials developed by Mishin et al. Comparison of these two calculations provides a means for further analysis of the efficacy of the potentials in atomistic modeling of more complicated configurations, such as extended defects.

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Study of the Mechanical Behavior of BCC Transition Metals Using Bond-Order Potentials

Cited by 5 publications

References 30 publications

Evaluating the effects of loading parameters on single-crystal slip in tantalum using molecular mechanics

Evaluating the effects of loading parameters on single-crystal slip in tantalum using molecular mechanics

Influence of non-glide stresses on plastic flow: from atomistic to continuum modeling

Higher-energy Structures and Stability of Cu and Al Crystals Along Displacive Transformation Paths

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