ATOMIC-STRUCTURE OF A DECAGONAL AL-CO-NI QUASI-CRYSTAL

A structure refinement of the decagonal quasicrystal Al70Co20Ni10 with the five-dimensional superspace group P10/mmm was made on the basis of single-crystal x-ray-diffraction data. The structure is a layer structure that consists of two kinds of layers stacked along the c (tenfold) axis with an interval of c/2 (c=4.08). The structure has a local-atom arrangement similar to that of monoclinic Al13Fe4, but includes stacking disorder of the layers. The model explains well the diffraction intensity, chemical composition, and density. There exists another model with P105mc, which gives a diffraction intensity similar to that of the above model, except for the extinct reflections due to the extinction rule of the superspace group. © 1990 The American Physical Society.