Direct observation of domains and discommensurations in Mn-Si-Al octagonal quasicrystal by transmission electron microscopy

Domains and discommensurations have been directly observed by transmission electron microscopy in some dark-field images using certain reflections in a Mn-Si-Al octagonal quasicrystal. The invisibility and visibility of domains and discommensurations separate the diffraction spots into basic and satellite reflections. The domains and discommensurations observed in satellite reflections are interpreted as due to the ordering of Si and Al atoms in the quasilattice of the quasicrystal. A simple model which gives satisfactory agreement with the experimental results is given.