Structure refinement of (Al, Zn)(49)Mg-32-type phases by single-crystal X-ray diffraction

Detailed structures of (Al, Zn)(49)Mg-32-type crystalline phases, which are closely related to the Mg-Al-Zn icosahedral quasicrystal in Mg40Al60-xZnx (x=14-51) alloys, were examined by single-crystal X-ray diffraction analysi s. The structures have been determined with final R factors less than 0.04, and show good correspondence between chemical compositions obtained from s tructural refinements and those determined by electron probe microanalysis. The refined structures are somewhat different from that proposed by Bergma n et al. [G. Bergman, J.L.T. Waugh, L. Pauling, Acta Crystallogr. 10 (1957) 254] in that they have no central atom in the Bergman-type atom cluster. T he atom site occupancy is also discussed as a function of Zn content. (C) 2 000 Elsevier Science B.V. All rights reserved.