2mm symmetry

2mm Symmetry
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Figure 2999a shows the whole-pattern symmetry and projection-diffraction symmetry of the [1-100] CBED patterns of T1 (Al₂CuLi) crystals. [2] The symmetries of both patterns are 2mm. The projection-diffraction symmetry in Figures 2999a(b) does not show perfect 2mm symmetry due to slight misalignment of the second condenser aperture.


(a)	(b)

Figure 2999a. [1-100] CBED patterns of T1 (Al₂CuLi) crystals: (a) whole-pattern symmetry (HOLZ) and (b) projection-diffraction symmetry in ZOLZ. Adapted from [2]

Figure 2999b shows an electron diffraction pattern obtained from Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5 in [100] zone axis. This crystal system belongs to space group I4/mmm and the diffraction pattern have 2mm Symmetry.

$Electron diffraction pattern obtained from Zr41Ti14Cu12.5Ni10Be22.5 in [100] zone axis$

Figure 2999b. Electron diffraction pattern obtained from Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5 in [100] zone axis. The lattice parameters are a = 0.34 nm, and c = 1.137 nm. [1]

[1] Q. Wei, N. Wanderka, P. Schubert-Bischoff, and M-P. Macht, S. Friedrich, Crystallization phases of the Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5 alloy after slow solidification, J. Mater. Res., 15 (8) 1729, (2000).
[2] Kenneth S. Vecchio and David B. Williams, Convergent Beam Electron Diffraction Analysis of the T1 (Al2CuLi) Phase in Al-Li-Cu Alloys, Metallurgical Transactions A, 19A, 1988-2885, (1988).

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