Electron microscopy
 
P4/mbm (127) Space Group
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Table 1541a. P4/mbm (127) space group.

Name in the International Tables for Crystallography
P4/mbm P
123 4/mmm
Crystal system
Tetragonal 4/mmm
Asymm
0 ≤ x ≤ 1/2 and 0 ≤ y ≤ 1/2 and 0 ≤ z ≤ 1/2 and y ≤ 1/2-x
16 Absence of reflections

 

Translation
 
Symmetry (atomic coordinates)
X, Y, Z; -X, -Y, Z; -Y, X, Z; Y, -X, Z; 1/2-X, 1/2+Y, -Z; 1/2+X, 1/2-Y, -Z; 1/2+Y, 1/2+X, -Z; 1/2-Y, 1/2-X, -Z; -X, -Y, -Z; X, Y, -Z; Y, -X, -Z; -Y, X, -Z; 1/2+X, 1/2-Y, Z; 1/2-X, 1/2+Y, Z; 1/2-Y, 1/2-X, Z; 1/2+Y, 1/2+X, Z
Crystal examples
 

Table 1541b. C4/mmb (127) space group.

Name in the International Tables for Crystallography
C4/mmb (D4h5)  
   
Crystal system
Tetragonal  
Asymm
 
  Absence of reflections

 

Translation
 
Symmetry (atomic coordinates)
 
Remarks
The unit-cell axes double only along a and b, and thus in electron diffraction pattern, half-integral reflections are found for h and k, but with l integral. For distorted perovskites, the adjacent octahedra along the c-axis are rotated in inphase (+) manner.
Crystal examples
NaNbO3, CsCaCl3 and CsPbCl3.

 

 

 

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