Z-contrast imaging of decagonal quasicrystals: an atomistic model of growth

The structure of Al-Ni-Co decagonal quasicrystals is studied by atomic-reso lution Z-contrast imaging technique. We propose that the presence of "rotat ional ordering" is the key reason leading to the formation of the 2 nm clus ters and the overlaps necessary in the coverage model. Every detail of the Z-contrast images of the 2 nm clusters can be reproduced by a superposition of rotational variants of the 2 nm clusters seen in the ordered tau (2)-in flated Al13Co4 approximant phase. introducing this rotational ordering, it is clear how one cluster can nucleate neighboring clusters. Continuing this process automatically generates all the intercluster separations necessary for quasiperiodic tiling. (C) 2000 Elsevier Science B.V. All rights reserv ed.