Atomic-resolution Z-contrast provided direct images of chemical disorder and columnar vacancies in an ideal decagonal quasi-crystal. Chemical disorder occurred in the central ring of the 2nm clusters, and involved both Al and Ni(Co) atoms. Columnar vacancies were observed in the form of closely-spaced half-occupied atomic columns in specific rings within the clusters. This structure, deduced from real space images, differed significantly from previous atomic models.

Direct Imaging of Local Chemical Disorder and Columnar Vacancies in Ideal Decagonal Al-Ni-Co Quasicrystals. Y.Yan, S.J.Pennycook, A.P.Tsai: Physical Review Letters, 1998, 81[23], 5145-8