It was recalled that dislocations in quasicrystals could be observed by means of conventional diffraction-contrast transmission electron microscopy. The extinction conditions for dislocations were derived, within the framework of kinematic theory, for the case of 2-dimensional quasicrystals. As in the case of icosahedral quasicrystals, it was also expected that there would exist so-called weak-extinction conditions. That is, the dislocation could be in and out of contrast for co-linear vectors. The theory was presented in detail for the case of decagonal quasicrystals.

R.Wittmann: Philosophical Magazine Letters, 1995, 72[2], 87-91