mmm Point Group

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mmm Point Group

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 () 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 I_hkl = I_-hkl, for the mirror plane perpendicular to axis b we have I_hkl = I_h-kl, and for the mirror plane perpendicular to axis c, we have I_hkl = I_hk-l.

Practical Electron Microscopy and Database

An Online Book, Second Edition by Dr. Yougui Liao (2006)

mmm Point Group