High resolution X-ray and neutron diffraction of super- and disorder in decagonal Al–Co–Ni

Synchrotron measurements at DESY and ESRF of decagonal quasicrystals with the nominal composition Al70Co15Ni15 and Al72Co16Ni12, show that Bragg reflections with high |Hi∗| values are surrounded by up to four weak subsidiary peaks. The positions of these additional peaks depend solely on the position of the Bragg reflection in the reciprocal perpendicular subspace and can be explained by a linear phason strain model. This model sheds new light on the current superorder models [K. Hradil et al. Phil. Mag. A 79 (1999) 1963] and is a further step towards an understanding of the real structures of decagonal quasicrystals.