Abstract
Molecular dynamics simulations of crack propagation are performed for two extreme cases of complex metallic alloys. In a model quasicrystal the structure is determined by clusters of atoms, whereas the model C15 Laves phase is a simple periodic stacking of a unit cell. The simulations reveal that the basic building units of the structures also govern their fracture behaviour. Atoms in the Laves phase play a comparable role with the clusters in the quasicrystal. Although the latter are not rigid units, they have to be regarded as significant physical entities.