The peierls energy and kink energy in fcc metals

Abstract

In fcc crystals, dislocations are dissociated on the {111} glide plane into pairs of partial dislocations. Since each partial interacts individually with the Peierls potential and is coupled to its neighbour by a stacking fault, periodic variations in the separation distance d of the partials occur when dislocations running along closed packed lattice directions are displaced. This can drastically reduce the effective Peierls stress. By using the Peierls model the structure of 0°, 30°, 60° and 90° dislocations in a typical fcc metal with the elastic properties of Cu and a stacking-fault energy γ₀ in the interval 0.04 ≤ γ₀ ≤ 0.05 J/m² was studied, and the magnitude of the Peierls energy ΔE _P and the resulting kink energies E _K were determined. Since the energies involved are of the order of 10⁻³ eV/b or less, their magnitude cannot be asserted with high confidence, considering the simplifying assumptions in the model. The difference in the changes of the core configuration during displacement of dislocations of different orientations should, however, be of physical significance. It is found that a dissociated 60° dislocation generally has a higher effective Peierls energy than a screw dislocation, but the reverse is true for the kink energy, at least in Cu.

Acknowledgement

This work was supported by the Austrian Fonds zur Förderung der wissenschaftlichen Forschung (project P12990-PHY). We are grateful to Professor W. Pichl for help with the numerical evaluation and to W. Püschl for supplying the anisotropic elastic constants.

Notes

Dedicated to Prof. Alfred Seeger on the occasion of his 77th birthday on August 31, 2004.

Additional information

Notes on contributors

Maciej Krystian

Dedicated to Prof. Alfred Seeger on the occasion of his 77th birthday on August 31, 2004.