Alternative misfit dislocations pattern in semi-coherent FCC {100} interfaces

Abstract

The character of interface misfit dislocations is determined according to interface crystallography and minimization of interface energy, which includes coherent interface energy and dislocation line energy. The core energy of dislocations is generally ignored in such analysis. In this work, we demonstrate that the core energy of misfit dislocations is dependent on the mechanical and thermal loading condition, and ultimately determines the nature of interface misfit dislocation patterns (MDP). Employing atomistic simulations with empirical interatomic potentials, we show the transformation of conventional MDP consisting of a/2<110> dislocation into an alternative MDP consisting of mixed a<100> and a/2<110> dislocations under elevated temperatures and/or normal-to-interface tensile stresses. Although a<100> type dislocations typically have greater line energy in bulk, molecular statics/dynamics calculations show that a<100> type misfit dislocations are preferred over a/2<110> type under elevated temperatures and/or normal-to-interface tensile stresses due to their reduced core energy. In addition, we found that the a<100> dislocations possess significantly reduced vacancy formation energies compared to the a/2<110> dislocations. The potential application of this unique property of the alternative dislocation pattern for nanoscale multilayered composite as a functional material is discussed.