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Table 3553a and Figure 3553 show the monoclinic crystal systems and the schematic illustration of the monoclinic lattices, respectively.
Table 3553a. Monoclinic crystal systems.
Crystal
family 
Crystal
system 
Required
symmetries
of point group 
Point
group 
Space
group 
Bravais
lattices 
Lattice
system 
Monoclinic

1 twofold axis of rotation or 1 mirror plane 
3

13

2

Monoclinic 
Figure 3553. Schematic illustrations of the Bravais
lattices of monoclinic crystals.
Table 3553b. Relationship between Laue classes and point groups.
System 
Essential symmetry 
Lattice symmetry 
Laue class (Diffraction symmetry) 
Point Groups (Hermann–Mauguin notation) 
Triclinic 
None 


1, 1 
Monoclinic 

2/m 
2/m 
2, m, 2/m 
Orthorhombic 
222 or 2mm

mmm

mmm 
222, mm2, mmm 
Tetragonal 

4/mmm

4/m

4, 4, 4/m 
4/mmm 
422, 42m, 4mm, 4/mmm 
Trigonal 


3 
3, 3 
3m1 
321, 3m1, 3m1 
31m 
312, 31m, 31m 
Hexagonal 

6/mmm

6/m 
6, 6, 6/m 
6/mmm 
622, 62m, 6mm, 6/mmm 
Cubic 
23 
m3m

m3 
23, m3 
m3m 
432, 43m, m3m 
For monoclinic structures, the lattice spacing (dspacing) can be given by, (You can download the excel file for your own calculations)
 [3553]
where,
a, b and c  The lattice constants.
h, k, and l  The Miller indices.
In crystals, anisotropy of many properties clearly arises because the arrangement of their atoms varies in different directions. In general, cubic crystals is less anisotropic than monoclinic ones because of their greater symmetry, for instance, with respect to electrical conductivity. Therefore, cubic crystals do not exhibit electrical polarization when the temperature is changed, so that their pyroelectric effect is isotropic.
Table 3553c. Centrosymmetric, noncentrosymmetric, and chiral space groups for monoclinic crystal systems.
Crystal system 
Laue group 
Point group 
Space group 
Monoclinic 
2/m 
2 
P2, P2_{1}, C2 
m 
Pm, Pc, Cm, Cc 
2/m 
P2/m, P2_{1}/m, C2/m, P2/c, P2_{1}/c, C2/c 
Red: chiral; green: noncentrosymmetric; and yellow: centrosymmetric. 
Table 3553d. Other characteristics of monoclinic structures.
Contents 
Page 
Angles in unit cells 
page3555 
Volume of unit cells 
page3033 
Bravais lattices 
page4546 
Relationship between threedimensional crystal families, crystal systems, space group, point group, lattice systems and symmetries 
page4549 
