Weak Bragg scattering in icosahedral Mg-Y-Zn

The mathematical framework of higher-dimensional crystallography intrinsica lly assumes the ideally perfect crystal as the underlying basis for solving , modelling and refining crystal structures with a quasiperiodic ordering s cheme. Such an ideally perfect crystal will result in a Fourier spectrum wi th sharp Bragg peaks and no diffuse scattering. However, most quasicrystall ine materials do exhibit diffuse scattering phenomena, and therefore contai n a certain amount of disorder. Only recently, single-crystals from the sys tem Mg-Y-Zn emerged as possible candidates for ideally perfect crystals. We employed X-ray diffraction techniques on a particular sample of Mg-Y-Zn. T echniques, based on area detector systems, which are usually used to study weak diffuse scattering phenomena, are employed. There is no indication of disorder diffuse scattering which normally obscures the weak Bragg scatteri ng. The experimental conditions are discussed under which a full data colle ction may he performed with area detectors. (C) 2000 Elsevier Science B.V. All rights reserved.