Structural model for the Al72Ni20Co8 decagonal quasicrystals

We propose a structure model for the Al72Ni,Co-20(8) decagonal quasicrystal s based on its tau(2)-inflated Al13Co4 approximant phase: Applying a 10(5) screw operation on a monolayer obtained from the approximant reproduces alm ost all features of 2-nm clusters seen in atomic-resolution Z-contrast imag es of Al72Ni20Co8 decagonal quasicrystals. The exception is the central rin g, where the symmetry is broken due to chemical ordering of Al and transiti on metals. By restricting possible overlaps, this enforces the perfect quas iperiodic tiling.