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Structure determination of a pseudo-decagonal quasicrystal approximant by the strong-reflections approach and rotation electron diffraction.
- Source :
- Journal of Applied Crystallography; Apr2016, Vol. 49 Issue 2, p433-441, 8p
- Publication Year :
- 2016
-
Abstract
- The structure of a complicated pseudo-decagonal (PD) quasicrystal approximant in the Al-Co-Ni alloy system, denoted as PD1, was solved by the strong-reflections approach on three-dimensional rotation electron diffraction (RED) data, using the phases from the known PD2 structure. RED shows that the PD1 crystal is primitive and orthorhombic, with a = 37.3, b = 38.8, c = 8.2 Å. However, as with other approximants in the PD series, the superstructure reflections (corresponding to c = 8.2 Å) are much weaker than those of the main reflections (corresponding to c = 4.1 Å), so it was decided to solve the PD1 structure in the smaller primitive unit cell first, i.e. with unit-cell parameters a = 37.3, b = 38.8, c = 4.1 Å and space group Pnam. A density map of PD1 was calculated from only the 15 strongest unique reflections. It contained all 31 Co/Ni atoms and many weaker peaks corresponding to Al atoms. The structure obtained from the strong-reflections approach was confirmed by applying direct methods to the complete RED data set. Successive refinement using the RED data set resulted in 108 unique atoms (31 Co/Ni and 77 Al). This is one of the most complicated approximant structures ever solved by electron diffraction. As with other approximants in the PD series, PD1 is built of characteristic 2 nm wheel clusters with fivefold rotational symmetry, which agrees with results from high-resolution electron microscopy images. The simulated electron diffraction patterns for the structure model are in good agreement with the experimental electron diffraction patterns obtained by RED. [ABSTRACT FROM AUTHOR]
- Subjects :
- QUASICRYSTALS
CONDENSED matter
ELECTRON diffraction
WAVE diffraction
CRYSTALS
Subjects
Details
- Language :
- English
- ISSN :
- 00218898
- Volume :
- 49
- Issue :
- 2
- Database :
- Complementary Index
- Journal :
- Journal of Applied Crystallography
- Publication Type :
- Academic Journal
- Accession number :
- 115376309
- Full Text :
- https://doi.org/10.1107/S1600576716000042