Key role of excess atomic volume in structural rearrangements at the front of moving partial dislocations in copper nanocrystals.

Here we report on a molecular dynamics simulation of the atomic volume distribution in fcc copper with moving partial dislocations 1/6 〈112〉 {111}. The simulation shows that the leading and trailing partial dislocations surrounding a stacking fault move via local fcc→hcp and hcp→fcc transformations and that a fcc-hcp transition zone exists in which the atomic volume is larger than that in the perfect close-packed structure. The excess volume is five to seven percent, which compares with volume jumps on melting. The simulation results agree with experimental data showing that the nucleation of dislocations is preceded by the formation of regions with an excess atomic volume.