d = 6 nm show the formation of many voids that rapidly
coalesce to form a macrocrack. Immediately prior to
failure a classical (nearly) smooth crack forms with
few voids elsewhere in the system (Fig. 2(c)). On the
other hand, the simulations for d = 2 nm show continual
nucleation of new cavities. Eventually, some of these
cavities coalesce into a failure-producing defect that
spans the system. This difference in behavior leads to
very large strains to failure (50%, see Fig. 2(i)) in the
2 nm sample as compared with the relatively small
strains to failure in the 4 nm (18%, see Fig. 2(f)) and
6 nm (13%, see Fig. 2(c)) samples. While all samples
eventually fail via a void coalescence process, the difference
in failure mode between the 4 nm/6 nm samples and the
2 nm sample appears as brittle vs. ductile failure behavior.