Decagonal quasicrystal with ordered body-centred (CsCl-type) hypercubic lattice

An ordered structure, which was found in a decagonal quasicrystal with 0.4 nm periodicity in a conventionally solidified Al70Ni20Ru10 alloy, has been examined theoretically by the projection of an ordered body-centred (CsCl-t ype) hypercubic lattice. The ordered structure can be characterized as an o rdered arrangement of two kinds of atom columnar cluster with different dir ections of pentagonal symmetry. Two lattices, which are constructed by conn ecting the atom clusters in the same directions, can be interpreted as orde red sublattices formed by each of vertex and body-centred positions of the CsCl-type hypercubic lattice. Diffraction patterns calculated from the orde red and disordered body-centred hypercubic lattices replicate well the elec tron diffraction patterns observed from the Al-Ni-Ru and other decagonal qu asicrystals.