Peierls stress and Peierls energy of a 70.5° ⟨1 1 1⟩ dislocation in Mo

Abstract

The Peierls potential and the Peierls stress of a 70.5° ⟨1 1 1⟩dislocation with line orientation along the [1 1 1] direction and Burgers vector in Mo are studied using two slightly different profiles of the γ-surface from the literature. Since the Burgers vector has a large edge component, the dislocation has a well-defined glide plane. Therefore, its core structure can be studied following the procedure of the Peierls model generalized as variational problem. The model allows differentiating between the (long range) elastic self-energy and the (local) atomic misfit energy in the glide plane. When in the Rayleigh–Ritz method the variational trial functions are assumed to be Peierls dislocations, it is possible to calculate analytically the changes in elastic energy during the translation of the dislocation centre. It turns out that these changes in elastic energy can be very large and reduce the ‘effective Peierls energy’ to a small fraction of the changes in atomic misfit energy. The results depend sensitively on finer details of the γ-surface. The calculations can be performed on a laptop in a time scale of minutes.

Keywords:

• Peierls energy
• Peierls stress
• bcc
• Mo

Acknowledgement

Constructive criticism of A. Seeger is gratefully acknowledged.