Fracture and dislocation properties: An ab-initio electronic structure approach

The mechanisms of that underline the mechanical behavior of the ductile/brittle behavior and anomalous mechanical response of materials with interfaces are still far from being well understood and remain a challenge to theoretical explanation. These problems can be extremely difficult, since for example, in transition metals, accurate, microscopic descriptions of the directional covalent chemical bonding are required for modeling mesoscale phenomena (e.g. dislocations, crack tips). We present examples of fundamental studies of several aspects related with mechanical properties on the basis of ab-initio calculations of the cleavage and generalized stacking fault (GSF or γ-surface) energetics, the effects of impurities and transition-metal additions on Fe grain boundary cohesion, and extended-point defect interaction characteristics needed for further Peierls-Nabarro, Rice-Thomson and Rice-Wang theoretical analyses. We emphasize the importance of accurate, ab-initio electronic structure determinations of the interatomic interactions, the effects of local atomic relaxation, the electronic states on dislocations, and the dislocation structure and mobility needed for understanding the mechanical response of solids on a fundamental level.