Structure refinement of (Al, Zn)49Mg32-type phases by single-crystal X-ray diffraction

Detailed structures of (Al, Zn)49Mg32-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 analysis. The structures have been determined with final R factors less than 0.04, and show good correspondence between chemical compositions obtained from structural refinements and those determined by electron probe microanalysis. The refined structures are somewhat different from that proposed by Bergman 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. The atom site occupancy is also discussed as a function of Zn content.