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M: Metallphysik

M 6: Quasikristalle II

M 6.4: Fachvortrag

Monday, March 26, 2001, 12:30–12:45, S5.3

Structure model for the variant ’basic’ of the decagonal phase Al–Co–Ni — •Max Scheffer — Materials Research and Liquids, Institute of Physics, TU Chemnitz

The description of the structures of decagonal quasicrystals by tilings, which are covered by intersecting clusters, becomes a promising approach^1,2. In this description points of interest are the corresponding tiling as well as the structure of the clusters.

A structure model of the high temperature Ni-rich decagonal phase ’basic’ in Al–Co–Ni was investigated, which is generated by the cut & projection method. The acceptance domains are very simple and describe a structure which exhibits small decagonal clusters with a twofold centre and a diameter of 6.5 Å, which results in a small number of atoms per cluster. The centres of the clusters describe a tiling with an edgelength of 7.6 Å. This tiling and its Inflations can be compared to those found in experimental investigations³. The density of the structure model is 3.91 g/cm³ and the stoichiometry (72.36 at.% Al) matches to the existence region of the decagonal phase⁴.

1. P. Gummelt, Geometriae, 62, 1-17, (1996).
2. P.J. Steinhardt, H.-C. Jeong, K. Saitoh, M. Tanaka, E. Abe and A.P. Tsai, Nature 396, 55-57 (1998).
3. S. Ritsch, C. Beeli, H.-U. Nissen, T. Gödecke, M. Scheffer and R. Lück, Phil. Mag. Lett., 74, 99-106 (1996).
4. T. Gödecke, M. Scheffer, R. Lück, S. Ritsch and C. Beeli, Z. Metallkd. 89,687-698, (1998).