Lattice resistance and Peierls stress in finite size atomistic dislocationsimulations

Atomistic computations of the Peierls stress in fcc metals are relatively s carce. By way of contrast, there are many more atomistic computations for b ce metals, as well as mixed discrete-continuum computations of the Peierls- Nabarro type for fcc metals, One of the reasons for this is the low Peierls stresses in fcc metals. Because atomistic computations of the Peierls stre ss take place in finite simulation cells, image forces caused by boundaries must either be relaxed or corrected for if system size-independent results are to be obtained. One of the approaches that has been developed for trea ting such boundary forces is by computing them directly and subsequently su btracting their effects, as developed in (Shenoy V B and Phillips R 1997 Ph il. Mag. A 76 367), That work was primarily analytic, and limited to screw dislocations and special symmetric geometries. We extend that work to edge and mixed dislocations, and to arbitrary two-dimensional geometries, throug h a numerical finite element computation. We also describe a method for est imating the boundary forces directly on the basis of atomistic calculations . We apply these methods to the numerical measurement of the Peierls stress and lattice resistance curves for a model aluminium (fcc) system using an embedded-atom potential.