Atomistic simulations were used to investigate how the stress required for the homogeneous nucleation of partial dislocations, in monocrystalline Cu under uniaxial tension, changed as a function of the crystallographic orientation. Molecular dynamics was used, with an embedded-atom method potential for Cu at 10 and 300K. The results indicated that non-Schmid parameters were required to describe dislocation nucleation for certain single crystal orientations. It was found that the stereographic triangle could be divided into 2 regions: one where dislocation nucleation was dominated by the conventional Schmid factor (the resolved shear stress in the direction of slip) and one where dislocation nucleation was dominated by the normal factor (the resolved stress normal to the slip plane). A continuum relationship was derived that incorporated Schmid and non-Schmid terms in order to correlate the stress required for dislocation nucleation over all tensile axis orientations within the stereographic triangle. It was notable that the simulation results could be expressed as an atomistically-based continuum formulation for partial dislocation loop nucleation in face-centred cubic single crystals.

Atomistic Simulations of Homogeneous Dislocation Nucleation in Single Crystal Copper. M.A.Tschopp, D.E.Spearot, D.L.McDowell: Modelling and Simulation in Materials Science and Engineering, 2007, 15[7], 693-709