Effects of H2O on Si fracture:: a hybrid quantum-classical simulation

The mechanism of stress corrosion cracking in Si has became recently important, because it occurs in micro-machines. A novel hybrid quantum-mechanical/molecular-dynamics simulation code developed recently for parallel computers is used to perform simulations for a cracked Si-model under tension (mode-I opening) with three H2O molecules around the crack front to investigate possible effects of both, saturation of dangling bonds of Si with hydrogen atoms and environment molecules on the fracture initiation. Our results demonstrate formation of Si-O-Si bond by chemical reaction, which occurs at the crack tip after dissociation of O atom from H2O molecule. Moreover, the reaction exhibits no energy barrier and the hydrogen saturation has no effect on H2O molecule pathway. (C) 2004 Elsevier B.V. All rights reserved.