The atomic structure of 1/1 -1/1 -1/1 approximants, where x ranged from 20.5 to 50.5, was determined as a function of the Al concentration by applying the Rietveld method to X-ray powder diffraction data. It was shown that the center of the cluster was only 10%-occupied by the Al atom, at x = 20.5, but became essentially vacant when x was greater than 30. The sites which corresponded to the vertex of the icosahedral cluster in the first shell were 80%-occupied by Zn atoms and the remaining sites were occupied by Al atoms, when x ranged up to 40.

Composition Dependence of the Atomic Structure of AlxMg39.5Zn60.5-x (20.5 < x < 50.5) 1/1 -1/1 -1/1 Approximants Determined by the Rietveld Method U.Mizutani, W.Iwakami, T.Takeuchi, M.Sakata, M.Takata: Philosophical Magazine Letters, 1997, 76[5], 349-56