Direct Imaging of Local Chemical Disorder and Columnar Vacancies in Ideal Decagonal Al-Ni-Co Quasicrystals

Abstract

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.