28 research outputs found
Periodic diffraction patterns for 1D quasicrystals
A simple model of 1D structure based on a Fibonacci sequence with variable
atomic spacings is proposed. The model allows for observation of the continuous
transition between periodic and non-periodic diffraction patterns. The
diffraction patterns are calculated analytically both using ``cut and project''
and ``average unit cell'' methods, taking advantage of the physical space
properties of the structure.Comment: 17 pages, 6 figures, the language was polished. References added:
[18], [23] & [28]. Paper accepted to Acta Physica Polonica
Re-refinement of AlCuRh decagonal quasicrystal with a quasilattice based on the generalized Penrose tiling
Approximant-based orientation determination of quasicrystals using electron backscatter diffraction
Orientation mapping of quasicrystalline materials is demonstrated using crystalline approximant structures in the technique of electron backscatter diffraction (EBSD). The approximant-based orientations are symmetrised according to the rotational point group of the quasicrystal, including the visualization of orientation maps using proper colour keys for quasicrystal symmetries. Alternatively, approximant-based orientation data can also be treated using pseudosymmetry post-processing options in the EBSD system software, which enables basic grain size estimations. Approximant-based orientation analyses are demonstrated for icosahedral and decagonal quasicrystals
Phason-flips refinement of and multiple-scattering correction for the d-AlCuRh quasicrystal
The origin of the characteristic bias observed in a logarithmic plot of the calculated and measured intensities of diffraction peaks for quasicrystals has not yet been established. Structure refinement requires the inclusion of weak reflections; however, no structural model can properly describe their intensities. For this reason, detailed information about the atomic structure is not available. In this article, a possible cause for the characteristic bias, namely the lattice phason flip, is investigated. The derivation of the structure factor for a tiling with inherent phason flips is given and is tested for the AlCuRh decagonal quasicrystal. Although an improvement of the model is reported, the bias remains. A simple correction term involving a redistribution of the intensities of the peaks was tested, and successfully removed the bias from the diffraction data. This new correction is purely empirical and only mimics the effect of multiple scattering. A comprehensive study of multiple scattering requires detailed knowledge of the diffraction experiment geometry