Dresden 2009 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 10: Intermetallic Phases II

MM 10.2: Vortrag

Montag, 23. März 2009, 16:15–16:30, IFW B

Structural interrelations between cubic icosahedral approximants of the Ru-Sb-Zn system — •Bernd Harbrecht and Ding-Bang Xiong — Department of Chemistry, Centre of Materials Science, Philipps University, 35032 Marburg, Germany

Structural complexity in intermetallics comes in different guises, often not just as one phase rather than - as result of small energy differences between compositionally and structurally intimately related phases - in bundles of phases. Positional and substitution disorder may be one cause, long-range vacancy ordering another [1]. More attention has been paid recently to (in)commensurately complex alloy structures, quasicrystals QCs, and quasicrystal approximants QCAs, in which unusual rotational symmetries are relinquished that usual 3D translation symmetry can guide matter to the state of rest. We will present new examples of QCAs we found in the Ru-Zn-Sb system by partly substituting Sb for Zn and Ru in Ru13-δZn128-δ* (hP564-4(δ-δ*)[2], yielding icosahedral approximants of idealised composition Ru26Sb24Zn67 (cF936), Ru13Sb12Zn81, and Ru13Sb6Zn87 (cF848), homotypic to Mo7Zn40Sn12 [3]. The structures will be discussed in the light of the hierarchical approach by decorating high symmetry points with clusters instead with atoms, here with double-Mackay M127 and M119 snub cube clusters with and without additional glue atoms.

[1] S. Thimmaiah, B. Harbrecht, J. Alloys Comp. 2006, 417, 45. [2] C. Allio, B. Harbrecht, Z. Anorg. Allg. Chem. 2006, 632, 2142. [3] H. Hillebrecht, V. Kuntze, K. Gebhardt, Z. Kristallogr. 1997, 212, 840.