A stable one-dimensional quasicrystal related to decagonal Al-Co-Ni

A stable one-dimensional quasicrystal has been found for Al-Co-Ni which is related closely to the decagonal phase in this system. It exists as a high- temperature state above 900 degrees C in a range of compositions between ap proximately 71 and 71.5at.% Al between 18at.% and 22at.% Co. The modulation length along the periodic direction in its pseudo tenfold diffraction patt erns is approximately 61 Angstrom. We show that the 20 Angstrom edge length defective rhomb tiling superimposed on to a corresponding high-resolution image, defined by centres of atomic clusters, can be considered as a subset of a phason-strained, 2.5 Angstrom edge length Penrose tiling that has the observed period. An ideal 20 Angstrom edge length tiling based on special configurations of this Penrose tiling can be chosen as a prototype for the observed experimental tiling.