Quantitative Analysis of Factors Controlling Criterion of Dislocation Nucleation in Nanoscale Copper Single-Crystal Nanowires

Abstract

The purpose of this study is to quantitatively evaluate the effect of three factors (Factor-1: Surface of nanoscale materials, Factor-2: Atomistic structure of surfaces, and Factor-3: Normal stress on active slip planes) on critical resolved shear stress (CRSS) of dislocation nucleation in nanoscale materials. We conducted atomistic simulations of tensile or compressive deformation for copper single-crystal nanowire models with different surface structure by varying the cross-section shape and crystal orientation. In all models, stacking faults occurred at the dislocation nucleation. Thus, we discussed the effect of the three factors on CRSS of the nanowire models by considering with the ideal shear strength along the Burgers vector of the partial dislocation under the effect of normal stress. The reduction of the ideal strength due to the presence of surfaces was estimated to be about 30 %. Our analyses revealed that CRSS in most of the models can be explained by considering Factor-1 and Factor-3 alone. CRSS in the other models much deviated (-20 ~ +200 %) from the projection by Factor-1 and Factor-3, suggesting that Factor-2 can play a major role in some cases.