It was recalled that the Peierls-Nabarro model had originally been developed in order to describe core spreading on the slip plane of a dislocation. It was noted that screw dislocations had more than one slip plane and were expected to dissociate in a non-planar fashion which reflected the symmetry about the screw axis. The Peierls-Nabarro model was here generalized in order to account for non-planar core spreading.

A.H.W.Ngan: Philosophical Magazine Letters, 1995, 72[4], 207-13