Electron microscopy
 
mmm Point Group
- Practical Electron Microscopy and Database -
- An Online Book -
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For many point groups, if the rotation axis can be unambiguously obtained from the combination of symmetry elements presented in the symbol, the n-fold rotation axes in n/m positions can then be ignored. From instance, the short symbol for 2/m 2/m 2/m (2/m 2/m 2/m) point group is mmm.

Table 2979 list all the space groups which have point group mmm.

Table 2979. All space groups which have point group mmm.
Space Group Patterson Space Group Number of Symmetry Operators Crystal System Laue Class Lattice Type
Pmmm 47 8 Orthorhombic mmm P
Pnnn 47 8 Orthorhombic mmm P
Pccm 47 8 Orthorhombic mmm P
Pban 47 8 Orthorhombic mmm P
Pmma 47 8 Orthorhombic mmm P
Pnna 47 8 Orthorhombic mmm P
Pmna 47 8 Orthorhombic mmm P
Pcca 47 8 Orthorhombic mmm P
Pbam 47 8 Orthorhombic mmm P
Pccn 47 8 Orthorhombic mmm P
Pbcm 47 8 Orthorhombic mmm P
Pnnm 47 8 Orthorhombic mmm P
Pmmn 47 8 Orthorhombic mmm P
Pmmn 47 8   mmm P
Pbcn 47 8 Orthorhombic mmm P
Pbca 47 8 Orthorhombic mmm P
Pnma 47 8 Orthorhombic mmm P
Cmcm 65 16 Orthorhombic mmm C
Cmca 65 16 Orthorhombic mmm C
Cmmm 65 16 Orthorhombic mmm C
Cccm 65 16 Orthorhombic mmm C
Cmma 65 16 Orthorhombic mmm C
Ccca 65 16 Orthorhombic mmm C
Fmmm 69 32 Orthorhombic mmm F
Fddd 69 32 Orthorhombic mmm F
Immm 71 16 Orthorhombic mmm I
Ibam 71 16 Orthorhombic mmm I
Ibca 71 16 Orthorhombic mmm I
Imma 71 16 Orthorhombic mmm I

mmm is the only centrosymmetric orthorhmbic point group. For the mirror plane perpendicular to axis a, we have the diffraction intensities Ihkl = I-hkl, for the mirror plane perpendicular to axis b we have Ihkl = Ih-kl, and for the mirror plane perpendicular to axis c, we have Ihkl = Ihk-l.

 

 

 

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