ISSN:
1600-5740
Quelle:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Thema:
Chemie und Pharmazie
,
Geologie und Paläontologie
,
Physik
Notizen:
Al5.103(Fe, Cr), orthorhombic, Imm2, a = 12.34, b = 12.41, c = 30.71 Å, V = 4701 Å3, atoms/cell = 305 (average), Dx \simeq 3.4 g cm−3. A structural model of the non-Fibonacci approximant O-AIFeCr with composition Al5.103(Fe, Cr) found in an Al12Fe2Cr alloy has been derived from its high-resolution electron microscopy images and the structure of the hexagonal \mu-Al4Mn [Shoemaker, Keszler & Shoemaker (1989). Acta Cryst. B45, 13–20], being isostructural to \mu-Al4Cr. Among the 14 unique positions of transition metal (TM) atoms, 13 are icosahedrally coordinated: five of these icosahedra interpenetrate into each other, forming icosahedral chains along [010], and the remaining eight icosahedra with their twofold axis parallel to this axis. This structural model describes a (010) layer structure with a sequence P^{m}FP(P^{m}FP)_I, where a flat layer F (a mirror plane) is sandwiched between two puckered P and Pm layers, and (P^{m}FP)I is related to P^{m}FP through a body-centred translation. The interatomic distances are 2.51–2.74 Å for TM—TM, 2.38–2.99 for TM—Al and 2.41–3.18 Å, for Al—Al. Simulated images and electron diffraction patterns calculated based on this structural model are comparable with the experimentally observed results.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1107/S0108768197000220
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