Atomistic simulations of homogeneous dislocation nucleation in single crystal copper

Atomistic simulations are used to investigate how the stress required for homogeneous nucleation of partial dislocations in single crystal copper under uniaxial tension changes as a function of crystallographic orientation. Molecular dynamics is employed based on an embedded-atom method potential for Cu at 10 and 300 K. Results indicate that non-Schmid parameters are required to describe dislocation nucleation for certain single crystal orientations. Specifically, we find that the stereographic triangle can be divided into two regions: a region where dislocation nucleation is dominated by the conventional Schmid factor ( the resolved shear stress in the direction of slip) and a region where dislocation nucleation is dominated by the normal factor ( the resolved stress normal to the slip plane). A continuum relationship that incorporates Schmid and non-Schmid terms to correlate the stress required for dislocation nucleation over all tensile axis orientations within the stereographic triangle is presented. The significance of this work is that simulation results are cast into an atomistically inspired continuum formulation for partial dislocation loop nucleation in face-centered cubic single crystals.