Structure Analysis of a Hyper-Complex Approximant to Icosahedral Quasicrystal using 3D Electron Diffraction Tomography

Analyzing the crystal structure of approximants is of vital importance in deriving structural information of building units (or basic clusters) and their arrangements toward icosahedral quasicrystals (IQCs). The acquired knowledge is essential in performing a hyper-space modeling, which is the only feasible way of today to elucidate the structural details of IQC’s. Since approximants are periodic crystals, conventional single-crystal X-ray diffraction can in principle be applied to analyze their atomic structure. However, the task becomes quite challenging when it comes to the case of approximants to Al-based F-type IQCs, Al-Pd-TM (TM = transition metal) [1]. These approximants often have very large unit cells with lattice constants of over a few tens of Angströms [2]. A recent study also suggests that, except for the solved case of [2], it is often very difficult to grow single crystals having coherent crystallinity within the width of the incident X-ray beam. It is therefore desirable if the crystal structure can be assessed using electron diffraction from a sub-micron sized crystal domain.