X-ray photoelectron diffraction study of the approximant Al 5 Co 2 (001) quasicrystal.

The intermetallic Al ₅ Co ₂ is defined as a structurally complex material and is considered a low-order quasicrystalline approximant. A single crystal of Al ₅ Co ₂ (001) was obtained by the Czochralski method. The sample was characterized by X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and X-ray photoelectron diffraction (PED). The surface composition was also analyzed by XPS, indicating only Al and Co compounds. In the current research, the crystal structure was qualitatively analyzed using the LEED patterns for different incident beam energies indicating a (1 × 1) termination, also in accordance with some literature works. The structure study was performed by applying the standard software MSCD and showed a (1 × 1) pattern. In addition, four different termination models for this termination were tested. The reliability factor indicated that the best termination belongs to the Al-rich surface layer.