The critical energy release rate defined as Gc = 2γ + γp (where, γ is the cohesive energy and γp is the plastic work) is widely used as a macroscopic fracture criterion. During embrittlement of Aluminum by Gallium, impurity segregation is localized to a small region along the grain boundary and the bulk plastic properties is unaffected. Yet, the critical energy release rate (which is predominan...