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Total-energy pseudopotential calculations are used to study the cleavage fracture processes in silicon. It is shown that bonds break continuously and cracks propagate easily on 111 and 110 planes provided crack propagation proceeds in the 〈1̄10〉 direction. In contrast, if the crack is driven in a 〈001〉 direction on a 110 plane the bond breaking process is discontinuous and associated with pronounced relaxations of the surrounding atoms. The discontinuous process is partly a result of some load sharing between the crack tip bond and the neighbouring bond, which results in a large lattice trapping. The different lattice trapping for different crack propagation directions can explain the experimentally observed cleavage anisotropy in silicon single crystals.
Pérez et al. (Fri,) studied this question.