Abstract
The stress distribution near a crack tip and crack propagation in a β-silicon nitride crystal are investigated by molecular dynamics (MD) simulations. A crack propagates when KI is greater than 0.7MPa√m. On the other hand, it shrinks when KI is smaller than 0.65MPa√m, indicating that the KIC value is about 0.7MPa√m. This value agrees well with that calculated using Griffith's theory. The stress distribution near the crack tip for KI is 0.7MPa√m, i.e. the case when the crack stops, is calculated from the MD results, assuming that the stress is the average of the atomic stresses. The calculated stress distribution is in good agreement with the linear elastic solution.
