Electron microscopy
 
2/m Point Group
- Practical Electron Microscopy and Database -
- An Online Book -
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The notation '2/m' in point group 2/m denotes a two-fold axis parallel to the normal to a mirror plane. The '/' symbol indicates parallel symmetry elements.

Table 2982 list all the space groups which have point group 2/m.

Table 2982. All space groups which have point group 2/m.
Space Group Patterson Space Group Number of Symmetry Operators Crystal System Laue Class Lattice Type
P2/m 10 4 Monoclinic 2/m P
P21/m 10 4 Monoclinic 2/m P
C2/m 12 8 Monoclinic 2/m C
P21/c 10 4 Monoclinic 2/m P
C2/c 12 8 Monoclinic 2/m C
P2/c 10 4 Monoclinic 2/m P

2/m is the only centrosymmetric monoclinic point group. For crystals with this point group, the combination of the two-fold axis (unique axis b) and the mirror plane leads to two sets of intensities of four equivalent reflections which are Ihkl = I-hk-l = I-h-k-l = Ih-kl and I-h-kl = I-hkl = Ihk-l = Ih-k-l.

 

 

 

 

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