The first atomistic calculations were made of the saddle-point configuration and activation energy for the nucleation of a 3-dimensional dislocation loop from a stressed crack tip in monocrystalline Cu. The transition state was found by using reaction pathway sampling schemes, nudged elastic band and dimer methods. For a (111)[110]-crack, typically loaded to 75% of the athermal critical strain energy release rate for spontaneous dislocation nucleation, the calculated activation energy was 1.1eV. This value was significantly higher than the continuum estimate.

Atomistic Study of Dislocation Loop Emission from a Crack Tip. T.Zhu, J.Li, S.Yip: Physical Review Letters, 2004, 93[2], 025503 (4pp)