Atomic-resolution $Z$-contrast images provide direct images of chemical disorder and columnar vacancies in an ideal Al-Ni-Co decagonal quasicrystal. Chemical disorder occurs in the central ring of the 2 nm clusters and involves both Al and Ni(Co) atoms. Columnar vacancies are observed in the form of closely spaced, half-occupied atomic columns in specific rings within the clusters. This structure, derived from real space images, differs significantly from previous atomic models.

• Received 24 August 1998

DOI:https://doi.org/10.1103/PhysRevLett.81.5145