Electron microscopy
 
Pentagonal Penrose Tiling
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Figure 1442a shows pentagonal Penrose tiling. The pentagonal Penrose pattern can be obtained by a single decagonal atomic surface as shown in Figure 1442a (b).

Pentagonal Penrose tiling
Decagonal atomic surface
(a)
(b)
Figure 1442a. (a) Pentagonal Penrose tiling, and (b) Decagonal atomic surface.

HAADF (high-angle annular dark-field) in a spherical aberration (Cs)-corrected STEM had been used to study the structure of an Al64Cu22Co14 decagonal quasicrystal (DQC) as shown in Figure 1442b. The bright dots in the HAADF-STEM image correspond to heavy atoms (z-contrast). 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. Figures 1442b (b) and (c) presents that almost all the brightest dots in the same part as Figure 1442b (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 1442b (d).

pentagonal tilings
pentagonal tilings
(a)
(b)
pentagonal tilings
pentagonal tilings
(c)
(d)
Figure 1442b. (a) HAADF image of an Al64Cu22Co14 decagonal quasicrystal (DQC), (b) Highlighted type I of pentagonal tilings in red, (c) Highlighted type II of pentagonal tilings in green, and (d) Both types of pentagonal tilings. Adapted from [1]

Figure 1442c shows the electron diffraction pattern of the Al64Cu22Co14 DQC (space group: P105/mmc) taken with the incident beam vertical to the image plane in Figure 1442b.

Al64Cu22Co14 decagonal quasicrystal (DQC) diffraction

Figure 1442c. Electron diffraction pattern of the Al64Cu22Co14 DQC (space group: P105/mmc). Adapted from [1]

 

 

 

 

 

 

 

 

 

 

 

 

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

 

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