Abstract
Molecular dynamic (MD) simulations of brittle microcrack growth in mode I show that initiation of the (001) [110] microcrack in α-iron can be treated in the framework of fracture mechanics. In agreement with experimental observations, the presented fracture parameters exceed several times the Griffith values, while the maximum crack velocity observed in MD-simulations is lower than that corresponding to the continuum prediction v_R (Rayleigh surface waves). Microcrack growth can be described by Freund's velocity function, if the terminal velocity v_m is replaced by the lower maximum velocity v_m. Near v_m, crack tip instabilities and branching have been observed under high loading. Present results indicate that microcrack branching can be expected especially under an impact loading.

Key words
molecular dynamic (MD) simulations, brittle microcrack, Rayleigh surface waves, α-iron

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