Atomistic aspects of the temperature effect on fracture toughness of a silicon single crystal

초록

The temperature effect on the fracture toughness of a Si single crystal was explored through molecular dynamics simulations over the temperature range of 1-1000 K. A sharp crack model with the (010)[00 1] (plane)[front] crystallographic system was considered, in which the interatomic force was characterized using the modified embedded atom method potential. The computational experiment of a mode-I fracture was carried out employing the displacement based on the mode-I near tip field, and the fracture toughness was evaluated using the critical stress intensity factor for the onset of crack growth. The results showed that the fracture toughness in the temperature range of 1-750 K slightly decreased with increasing temperature, where the effect of lattice trapping was reduced at the elevated temperature. However, when the temperature was higher than 800 K, the fracture toughness increased resulting from the nucleation of nanovoids in front of the crack tip. Detailed atomistic analysis showed that, in the small-scale yielding limit, the temperature effect on the hydrostatic component of the local crack tip field was important to crack-tip plasticity.

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