Molecular dynamics investigation of the effect of the interatomic potential on steady-state crack propagation

We present molecular dynamics simulations examining the effect of the interatomic potential on steady-state mode I crack propagation in a two-dimensional triangular lattice as a function of applied strain. The interatomic potential is the Morse potential whose failure strain exhibits linear variation with its exponential parameter. The limiting crack speed is defined to be the steady-state crack velocity observed at the onset of instability in steady-state crack propagation leading to dislocation nucleation or crack branching. For all systems studied, the limiting crack speed is observed to be less than one third the Rayleigh wave speed. The fastest crack propagation in these ideal systems is associated with a material's long-wavelength elastic properties being dominated by the strength of the nearest-neighbor bond.