A large columnar cluster of atoms in an Al-Cu-Rh decagonal quasicrystal studied by atomic-scale electron microscopy observations

We have found a columnar atomic cluster with a decagonal section of about 3.2 nm in diameter as a structural unit of an Al-Cu-Rh decagonal quasicrystal with 0.4 nm periodicity, using atomic-scale observations of high-resolution transmission electron microscopy (HRTEM) and high-angle annular detector dark-field (HAADF) scanning transmission electron microscopy (STEM). The decagonal cluster is tau times (tau is the golden ratio) the largest cluster (2.0 nm in diameter) previously found in Al-Ni-Co and Al-Pd-Mn decagonal quasicrystals. A structural model of the cluster is proposed from HRTEM and HAADF STEM images.