A numerical study was made of the energetics and atomic mechanisms of misfit dislocation nucleation and stress relaxation in a 2-dimensional atomistic model of strained epitaxial layers on a substrate with lattice misfit. Relaxation processes from coherent to incoherent states for various transition paths were studied by using interatomic potentials of Lennard-Jones type, plus a systematic saddle-point and transition-path search method. The method was based upon a combination of repulsive potential minimization and the nudged elastic band method. For a final state with a single misfit dislocation, the minimum-energy path and the corresponding activation barrier were obtained for various misfits and interatomic potentials. It was found that the energy barrier decreased strongly with misfit. Contrary to continuous elastic theory, a strong tensile-compressive asymmetry was observed. This asymmetry could be seen as being a manifestation of the asymmetry between the repulsive and attractive branches of the pair potential. It was found to depended sensitively upon the form of the potential.

Energetics and Atomic Mechanisms of Dislocation Nucleation in Strained Epitaxial Layers. O.Trushin, E.Granato, S.C.Ying, P.Salo, T.Ala-Nissila: Physical Review B, 2003, 68[15], 155413 (8pp)