Complex macroscopic plastic flow arising from non-planar dislocation core structures

For a broad range of crystalline materials complex dislocation core structures have a significant effect on macroscopic plastic flow, causing unexpected deformation modes that are strongly influenced by other components of stress in addition to the glide stress on a given slip system and on the sign of stress. In this paper we use atomistic simulations of a screw dislocation in bcc molybdenum to determine the dependence on orientation of the maximum resolved shear stress (in the direction of the Burgers vector) required to move the dislocation. A yield criterion that enters a continuum theory of bcc crystal plasticity and includes non-glide components of stress is developed along the lines of a general framework that was proposed several years ago. The predicted results are in excellent agreement with the atomistic simulations.