Table 1450. P10₅/mmc space group.

Both HAADF (high-angle annular dark-field) and ABF (annular bright-field) in a spherical aberration (C_s)-corrected STEM had been used to study the structure of an Al₆₄Cu₂₂Co₁₄ decagonal quasicrystal (DQC) as shown in Figure 1450a. The bright dots in the HAADF-STEM image correspond to heavy atoms (z-contrast), while the projective positions of Al atoms, those of transition-metal (TM) Cu/Co atoms, and mixed sites (MSs) of Al and TM atoms in the ABF-STEM image are indicated by the dark dots. This alloy was prepared by annealing at 1173 K for 24 h, subsequently cooling down to 1073 K at a cooling rate of 2 K/h, keeping at 1073 K for 72 h, and finally quenching in water.

Figure 1450b shows electron diffraction patterns of the Al₆₄Cu₂₂Co₁₄ DQC (in Figure 1450a) taken with the incident beam parallel to three primary axes. The diffraction patterns taken along directions q and p indicate that the structure includes two layers along the ten-fold axis and thus has centrosymmetry. The reflections marked by the arrows in Figure 1450b (c) disappear due to the existence of a 10₅ screw axis in the space group of P10₅/mmc.

Figure 1450c (a) shows the magnified image of the red-boxed part in Figure 1450b. Figures 1450c (b) and (c) presents that almost all the brightest dots in the same part as Figure 1450c (a) are arranged in two types of pentagonal tilings with an edge-length of 0.76 nm. In the two types of pentagonal tilings, there are ten dots without definite symmetry as marked by the white arrows in Figure 1450c (d).

(a)	(b)
(c)	(d)

[1] Kunio Yubuta, Kazuki Yamamoto, Akira Yasuhara and Kenji Hiraga, Structure of an AlCuCo Decagonal Quasicrystal Studied by C_s-Corrected STEM, Materials Transactions, 55(6), 866 (2014).