Combined atomistic simulation and continuum mechanics: Size-dependent behavior of atomistic simulation for brittle fracture in bcc-iron

The size-dependent behavior of atomistic simulation for brittle fracture in bcc-iron is studied using combined continuum-atomistic method. The result of displacement distribution at the crack tip indicates the radius of discrete region at the crack tip is about 120 Å, and the truncated distance of continuum elastic field is about 120 Å away from the crack tip. Further investigations of energy and atomic structure show that the elastic field of continuum mechanics cannot affect the crack tip processes effectively through the common region if the diameter of the atomistic region is smaller than 300 Å. We assume that the range of the system size that can bridge continuum with discrete region is at the scale of about 300 Å.