Shape transition and dislocation nucleation in strained epitaxial islands

We study numerically the equilibrium shape, shape transition and dislocation nucleation in strained epitaxial islands with a two-dimensional atomistic model, using interatomic potentials of Lennard-Jones type. The phase diagram for the equilibrium island shapes as a function of island size and lattice misfit with the substrate is obtained by an energy minimization procedure which does not require predefined faceted shapes. We determine the energy barrier and transition path for transition between different shapes of the islands and for dislocation nucleation in initially coherent islands using a method introduced recently, based on a systematic search of the transition paths for activated events. (AU)