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 C in a range of compositions between approximately 71 and 71.5at.% Al between 18at.% and 22at.% Co. The modulation length along the periodic direction in its pseudo tenfold diffraction patterns is approximately 61A. We show that the 20A 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, 2.5A edge length Penrose tiling that has the observed period. An ideal 20A edge length tiling based on special configurations of this Penrose tiling can be chosen as a prototype for the observed experimental tiling.