A nonplanar Peierls–Nabarro model and its application to dislocation cross-slip

Abstract

A novel semidiscrete Peierls-Nabarro model is introduced which can be used to study dislocation spreading at more than one slip planes, such as dislocation cross-slip and junctions. The strength of the model, when combined with ab initio calculations for the energetics, is that it produces essentially an atomistic simulation for dislocation core properties without suffering from the uncertainties associated with empirical potentials. Therefore, this method is particularly useful in providing insight into alloy design when empirical potentials are not available or not reliable for such multi-element systems. As an example, we study dislocation cross-slip and constriction process in two contrasting fcc metals, Al and Ag. We find that the screw dislocation in Al can cross-slip spontaneously in contrast with that in Ag, where the screw dislocation splits into two partials, which cannot cross-slip without first being constricted. The response of the dislocation to an external stress is examined in detail. The dislocation constriction energy and the critical stress for cross-slip are determined, and from the latter, we estimate the cross-slip energy barrier for straight screw dislocations.

Dislocation Mobility in a Quantum Crystal: The Case of SolidHe4

“…At a critical stress value, the so-called Peierls stress, an instability is reached and an equilibrium solution ceases to exist. [14,15] In this situation the dislocation becomes free to move through the crystal. The third line of This value is ∼ 3 orders of magnitude smaller than the shear modulus, which is consistent with the typical discrepancy between the ideal shear strength and actual yield stresses in crystals [1].…”

“…We compute the intrinsic dislocation structure and mobility of four different dislocation types using the multiscale paradigm of the semi-discrete Peierls-Nabarro (PN) model [13][14][15]. It constitutes a hybrid continuum-atomistic approach that captures the long-range elastic fields as well as the lattice-discreteness effects associated with the dislocation core.…”

Outils de simulation à l'échelle atomique pour traiter la chimie et la plasticité

“…La structure de coeur de différents métaux (e.g. Ni 3 Al (Schoeck 1999) [1], Al and Ag (Lu et al 2003) [2] et semi-conducteurs (e.g. Si (Joos et al 1994) [3]) ont ainsi été obtenue.…”

The Peierls—Nabarro Model of Dislocations: A Venerable Theory and its Current Development

“…We have recently developed the nonplanar SVPN model in order to study dislocation cross-slip and constriction in fcc metals [14]. As shown in Fig.…”

“…The planar model aims to treat a dislocation that is entirely confined to a single glide plane, while the nonplanar model deals with a dislocation that is spread onto more than one glide planes. The nonplanar model was developed in order to study stress-assisted dislocation cross-slip and constriction [14]. After the discussion of the models, we will apply the planar model to dislocations in Al with ab initio determined GSF energy surface.…”