The Peierls-Nabarro model revisited

We re-examine two important issues within the Peierls- Nabarro model, which are critical in obtaining accurate values for the Peierls stress. The firs t is related to the sampling scheme (double versus single counting) of the misfit energy across the glide plane and the second is the effect of atomic relaxation on the Peierls stress. We argue that the double-counting scheme is physically more appropriate. An analytical formula is derived for the P eierls stress of dislocations in alternating lattices. The atomic relaxatio n is shown to play an important role on the Peierls stress.