The crack-tip response to various loading conditions was studied. The immediate surroundings of the crack tip were described atomistically by using an embedded atom potential. An elastic finite-element region furnished the atomistically modelled crack tip with realistic boundary conditions. In agreement with experimental observations, perfectly brittle cleavage was observed only for the {110} crack plane. On the other hand, mode-I cracks on the {100} plane followed a zig-zag path, or emitted dislocations. Cracks which were injected into high-index planes emitted dislocations, deviated from the original crack plane and onto a {110} cleavage plane, or produced non-crystallographic rupture. Dislocation emission was also studied under mixed-mode loading. Regardless of the nature of the dislocation, emission was related to an almost constant mode-II energy release rate on the glide plane.

Cleavage Fracture and Crack-Tip Dislocation Emission in B2 NiAl: an Atomistic Study M.Ludwig, P.Gumbsch: Acta Materialia, 1998, 46[9], 3135-43