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Lattice resistance and Peierls stress in finite size atomistic dislocation simulations

Olmsted, David L. and Hardikar, Kedar Y. and Phillips, Rob (2001) Lattice resistance and Peierls stress in finite size atomistic dislocation simulations. Modelling and Simulation in Materials Science and Engineering, 9 (3). pp. 215-247. ISSN 0965-0393. doi:10.1088/0965-0393/9/3/308.

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Atomistic computations of the Peierls stress in fcc metals are relatively scarce. By way of contrast, there are many more atomistic computations for bcc metals, as well as mixed discrete-continuum computations of the Peierls-Nabarro type for fcc metals. One of the reasons for this is the low Peierls stresses in fcc metals. Because atomistic computations of the Peierls stress take place in finite simulation cells, image forces caused by boundaries must either be relaxed or corrected for if system size-independent results are to be obtained. One of the approaches that has been developed for treating such boundary forces is by computing them directly and subsequently subtracting their effects, as developed in (Shenoy V B and Phillips R 1997 Phil. Mag. A 76 367). That work was primarily analytic, and limited to screw dislocations and special symmetric geometries. We extend that work to edge and mixed dislocations, and to arbitrary two-dimensional geometries, through a numerical finite element computation. We also describe a method for estimating the boundary forces directly on the basis of atomistic calculations. We apply these methods to the numerical measurement of the Peierls stress and lattice resistance curves for a model aluminium (fcc) system using an embedded-atom potential.

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Phillips, Rob0000-0003-3082-2809
Additional Information:© 2001 IOP Publishing Ltd Received 8 November 2000, accepted for publication 8 March 2001, Print publication: Issue 3 (May 2001) We would like to thank Nitin Bhate, Ron Miller, Dnyanesh Pawaskar and S I Rao for helpful conversations. This work was partially supported by the DOE through Caltech’s ASCI Center for the Simulation of the Dynamic Response of Materials and the NSF under grant CMS-9971922 and through the MRSEC at Brown University. Note added in proof. After submitting this paper for publication, we became aware that R Wang and Q F Fang have recently computed the Peierls stress of the mobile edge dislocation for the same Ercolessi and Adams potential for aluminium, obtaining a value of 7.5 × 10^−5 μ [20, 21]. Our value, which is about 6 × 10^−5 μ, is in reasonable agreement with their result. This agreement may be coincidental, however, as their value is dominated by a term in their data fit with period √2a0/2. In our data the lattice resistance (for the edge dislocation) appears to be periodic with period √2a0/4 so that such a term would vanish.
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Deposited On:09 Feb 2006
Last Modified:08 Nov 2021 19:12

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