ALCHEMI Study of an Al72Ni20Co8Decagonal Quasicrystal

Two-dimensional channelling patterns, derived from variations in characteristic X-ray emission rates as a function of incident electron beam orientation, have been recorded from an Al 72 Ni 20 Co 8 decagonal quasicrystal for the first time. These channelling patterns indicate that the Al and transition metal atoms occupy different sets of sublattice sites, and that (to a good approximation) both Ni and Co atoms randomly occupy a similar set of sublattice sites, i.e. they are mutually disordered. This is shown to support the view that the structure of this alloy is determined primarily by the number of electrons per atom, e / a .