By means of reaction pathway analysis, we have investigated the nucleation of 90 • and 30 • partial dislocation from a sharp corner in an f.c.c. crystal copper. The anisotropy aspects of dislocation nucleation revealed by the results have shown that the stressdependent activation energy of 30 • partial dislocation is approximately twice over the counterpart of 90 • partial dislocation, and that the maximum inelastic displacement for the former is also higher. Moreover, the shape of the

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... int configuration of 30 • partial dislocation is similar to a half-ellipse whereas in the case of 90 • partial dislocation it is more like a semi-circle, reflecting the different Peierls barriers influenced by the Burgers vectors. Further study of the surface reconstruction demonstrates that although the nucleation of 30 • partial dislocation has been enhanced by surface reduction, it is still more energy-unfavorable than the 90 • partial dislocation. These results suggest that the higher Peierls barrier is responsible for the larger activation energy of 30 • partial dislocation nucleation.