Dislocation motion in icosahedral quasicrystals at elevated temperatures: Numerical simulation

We have simulated shear deformation of an icosahedral model quasicrystal at elevated temperatures with molecular dynamics. The generation of a dislocation loop was studied with a new visualization technique and a critical stress almost as large as the theoretical shear strength was measured. Built-in dislocations started to move at a temperature-dependent critical stress lower by one order of magnitude. While at zero temperature the dislocation propagated intermittently by large jumps, its motion became viscous as temperature increased. The dislocation cores bulged considerably owing to pinning at obstacles inherent in the structure. A calculation of the energy of a Peierls-Nabarro dislocation moving rigidly through the sample allowed us to determine the dominant obstacles. The results are considered in relation to two different models of quasicrystalline plasticity.