ENFORCEMENT OF MATCHING RULES BY CHEMICAL ORDERING IN THE DECAGONAL ALCUCO QUASI-CRYSTAL

An atomic structure model of the decagonal AlCuCo quasicrystal is proposed. The matching rules recently found by R. Klitzing et al. [Int. J. Mod. Phys. B (to be published)] for an abstract triangle tiling are enforced by specific Cu (Co) ordering, reducing the symmetry to P10(5)/m. The model renders very simple Kalugin's homology indices of (1,0) for Al and (0,1) for Cu (Co) and the ''magic'' Al composition of tau-1 almost-equal-to 0.618. Coupling of the chemical and phason disorders is suggested.