Screw dislocation structure and mobility in body centered cubic Fe predicted by a Gaussian Approximation Potential
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Authors
Maresca, F
Dragoni, D
Csányi, G
Marzari, N
Curtin, WA
Publication Date
2018-12-05Journal Title
npj Computational Materials
ISSN
2057-3960
Publisher
Springer Science and Business Media LLC
Volume
4
Issue
1
Type
Article
This Version
VoR
Metadata
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Maresca, F., Dragoni, D., Csányi, G., Marzari, N., & Curtin, W. (2018). Screw dislocation structure and mobility in body centered cubic Fe predicted by a Gaussian Approximation Potential. npj Computational Materials, 4 (1) https://doi.org/10.1038/s41524-018-0125-4
Abstract
The plastic flow behavior of bcc transition metals up to moderate
3 temperatures is dominated by the thermally activated glide of screw
4 dislocations, which in turn is determined by the atomic-scale screw dis-
5 location core structure and the associated kink-pair nucleation mech-
6 anism for glide. Modeling complex plasticity phenomena requires the
7 simulation of many atoms and interacting dislocations and defects.
8 These sizes are beyond the scope of first-principles methods and thus
9 require empirical interatomic potentials. Especially for the technolog-
10 ical important case of bcc Fe, existing empirical interatomic potentials
11 yield spurious behavior. Here, the structure and motion of the screw
12 dislocations in Fe are studied using a new Gaussian Approximation
13 Potential (GAP) for bcc Fe, which has been shown to reproduce the
14 potential energy surface predicted by density-functional theory (DFT)
and many associated properties. The Fe GAP predicts a compact,
16 non-degenerate core structure, a single-hump Peierls potential, and
17 glide on {110}, consistent with DFT results. The thermally-activated
18 motion at finite temperatures occurs by the expected kink-pair nucle-
19 ation and propagation mechanism. The stress-dependent enthalpy
20 barrier for screw motion, computed using the nudged-elastic-band
21 method, follows closely a form predicted by standard theories with a
22 zero-stress barrier of ∼ 1eV, close to the experimental value of 0.84eV,
23 and a Peierls stress of ∼ 2GPa consistent with DFT predictions of the
24 Peierls potential.
Sponsorship
Engineering and Physical Sciences Research Council (EP/L014742/1)
Engineering and Physical Sciences Research Council (EP/P022596/1)
Identifiers
External DOI: https://doi.org/10.1038/s41524-018-0125-4
This record's URL: https://www.repository.cam.ac.uk/handle/1810/287392
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