An experimental study on atomic-level unified criterion for brittle fracture

The aim of this study is to experimentally seek a unification of brittle fracture by an atomic-level criterion. In situ fracture experiments are carried out in transmission electron microscope by using notched nano-cantilever specimens of single-crystal silicon. On the basis of atomic fracture mechanics, the critical atomic energy release rate G_AFM^C at fracture is experimentally determined by combining finite element method and molecular statics calculations. It is found that G_AFM^C, of which the magnitude remains at a certain level regardless of the notch size, is an effective parameter to describe brittle fracture of a blunt notch. The comparison of the present G_AFM^C with those of macro-/nano-cracks reveals a good consistency, and this experimentally demonstrates a possible unification of brittle fracture of both a blunt notch and an ideal crack.