Numerical study of the athermal annihilation of edge-dislocation dipoles

The stability against recombination of narrow edge-dislocation dipoles of t he vacancy type is investigated in aluminium and copper by using atomistic- scale numerical simulation and phenomenological n-body potentials adapted t o these metals. Stable and metastable equilibrium positions of edge dipole configurations have been considered and the influence of the dissociation w idth has been examined. The calculations show that, in aluminium, edge dipo les athermally annihilate at distances much larger than the Burgers vector length of perfect dislocations while, in copper, the dislocations forming t he dipole recombine only when they are in close contact. These results are discussed in terms of surface energetics and in the framework of existing t heoretical and experimental work.