An Ab initio study of the cleavage anisotropy in silicon

Total-energy pseudopotential calculations are used to study the cleavage fr acture processes in silicon. It is shown that bonds break continuously and cracks propagate easily on {111} and {110} planes provided crack propagatio n proceeds in the (110) direction. In contrast, if the crack is driven in a (001) direction on a {110} plane the bond breaking process is discontinuou s and associated with pronounced relaxations of the surrounding atoms. The discontinuous process is partly a result of some load sharing between the c rack tip bond and the neighbouring bond, which results in a large lattice t rapping. The different lattice trapping for different crack propagation dir ections can explain the experimentally observed cleavage anisotropy in sili con single crystals. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.