P21/m (11) Space Group - Practical Electron Microscopy and Database - - An Online Book - |
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Table 1669a. P21/m (11) space group.
Table 1669b. P1121/m (11) space group.
For La4Cu3MoO12 crystals, both the absent reflections in the SAED [100] pattern in Figure 1669 (a) and the G-M lines in the 00l discs for odd l in the ZOLZ-CBED pattern taken along the [010] zone axis in Figure 1669 (b) indicate the presences of a 21 screw axis parallel to the c-axis and the forbidden reflection (00l: l≠2n). Moreover, the [010] WP (whole-pattern) in Figure 1669 (c) presents a mirror plane perpendicular to the c-axis. Therefore, according to the tables above, the La4Cu3MoO12 crystals belong to the P1121/m (11) space group.
Figure 1669. La4Cu3MoO12 (a ≈ 8 Å, b ≈ 7 Å, c ≈ 11 Å, γ ≈ 90°) crystals: (a) SAED pattern along [100] zone axis; (b) ZOLZ-CBED pattern along [010] zone axis. The black arrows indicate G-M lines visible in the 00l discs for odd l, and (c) Whole pattern presenting a mirror plane perpendicular to the c-axis. Adapted from [1]
[1] Sylvie Malo, Douglas A. Vander Griend, Kenneth R. Poeppelmeier, Yanguo Wang, Vinayak P. Dravid, Crystal symmetry of La3Cu2VO9 and La4Cu3MoO12 derived from the YAlO3 hexagonal structure by transmission electron microscopy, Solid State Sciences 3 (2001) 17–23.
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