We examine the conditions for dislocation nucleation beneath a plane strain rectangular indenter using atomistic simulations as well as analytic models, with the aim of (a) examining the validity of the analytic models and (b) extracting a nucleation criterion that can be used in mesoscopic dislocation dynamics models. Atomistic lattice statics calculations are performed using the quasicontinuum method, while the analytic analysis is carried out within the Rice-Thomson and Peierls-Nabarro frameworks. We find that both the atomistic and analytic models suggest a stress-based nucleation criterion. The features of the analytic models and quasicontinuum simulations are compared on the basis of the nucleation load and the incipient slip distribution. We find that the predictions of the analytical models are qualitatively borne out by the atomistic simulations, though quantitatively they are left wanting. Improvements to the analytical models to achieve quantitative agreement with the atomistic results are suggested.
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We are grateful to Marc Fivel, Alan Needleman, Christian Robertson, David Rodney and Erik van der Giessen for discussions. We would also like to acknowledge support through the Brown University MRSEC Program and the ASCI center at Caltech.