Band 219, Heft 7

Is quasicrystal structure analysis a never-ending story? Why is still not a single quasicrystal structure known with the same precision and reliability as structures of regular periodic crystals? What is the state-of-the-art of structure analysis of axial quasicrystals? The present comprehensive review summarizes the results of almost twenty years of structure analysis of axial quasicrystals and tries to answer these questions as far as possible. More than 2000 references have been screened for the most reliable structural models of pentagonal, octagonal, decagonal and dodecagonal quasicrystals. These models, mainly based on diffraction data and/or on bulk and surface microscopic images are critically discussed together with the limits and potentialities of the respective methods employed.

A great number of stable and metastable structures associated with the Al—Ni—Co decagonal phase were observed in a continuous range from binary Al—Co to binary Al—Ni. Two independent basic binary compounds forming the continuous row of the decagonal solid solutions are argued for Al—Ni—Co. The formation of different quasiperiodic and periodic structures in this range is discussed. Our analysis leads to a significant simplification of the description of the decagonal range in the equilibrium Al—Ni—Co phase diagram.

The bicyclic carboxylic acid, C 17 H 22 O 5 , a potential intermediate in the synthesis of bioactive δ -cuparenol has been prepared and characterized by spectroscopic and X-ray studies. The structure derived from the NMR data, the infrared spectra and the chemical analysis is consistent with that of single crystal X-ray analysis. The molecules in the title compound are linked into a three dimensional framework by O—H…O and C—H…O intermolecular hydrogen bonds. The supramolecular assembly of molecules exhibits R 4 4 (23) rings. The conformational analysis of the molecule as investigated by the semi-empirical quantum mechanical AM1 calculations shows a good agreement with the X-ray structure.