The 32 Crystal Classes | |||||||||||||||||||
Crystal system |
Crystal Class |
2-fold axes |
3-fold axes |
4-fold axes |
6-fold axes |
mirror planes |
inversion |
Examples |
Number of symmetry elements |
Generating matrices |
rank 1 tensors1 |
rank 2 symmetric tensors2 |
rank 2 asymmetric tensors |
rank 3 tensors3 |
rank 4 tensors |
Group elements | |||
Triclinic |
triclinic-pedial |
1 |
C1 |
- |
- |
- |
- |
- |
n |
|
1 |
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triclinic-pinacoidal |
1 |
S2 = Ci |
2: P1 |
- |
- |
- |
- |
- |
y |
2 |
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Monoclinic |
monoclinic-sphenoidal |
2 |
C2 |
3: P2, 4: P21, 5: C2 |
1 |
- |
- |
- |
- |
n |
4: sucrose |
2 |
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monoclinic-domatic |
m |
C1h = Cs |
6: Pm, 7: Pc, 8: Cm, 9: Cc |
- |
- |
- |
- |
1 |
n |
|
2 |
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monoclinic-prismatic |
$\frac{2}{m}$ |
C2h |
10: P2/m, 11: P21/m, 12: C2/m, 13: P2/c, 14: P21/c, 15: C2/c |
1 |
- |
- |
- |
1 |
y |
|
4 |
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Crystal system |
Crystal Class |
2-fold axes |
3-fold axes |
4-fold axes |
6-fold axes |
mirror planes |
inversion |
Examples |
Number of symmetry elements |
Generating matrices |
rank 1 tensors1 |
rank 2 symmetric tensors2 |
rank 2 asymmetric tensors |
rank 3 tensors3 |
rank 4 tensors |
Group elements | |||
Orthorhombic |
orthorhombic-disphenoidal |
222 |
V = D2 |
16: P222, 17: P2221, 18: P21212, 19: P212121, 20: C2221, 21: C222, 22: F222, 23: I222, 24: I212121 |
3 |
- |
- |
- |
- |
n |
|
4 |
|||||||
orthorhombic-pyramidal |
mm2 |
C2v |
25: Pmm2, 26: Pmc21, 27: Pcc2, 28: Pma2, 29: Pca21, 30: Pnc2, 31: Pmn21, 32: Pba2, 33: Pna21, 34: Pnn2 35: Cmm2, 36: Cmc21, 37: Ccc2, 38: Amm2, 39: Aem2, 40: Ama2, 41: Aea2, 42: Fmm2, 43: Fdd2, 44: Imm2, 45: Iba2, 46: Ima2 |
1 |
- |
- |
- |
2 |
n |
|
4 |
||||||||
orthorhombic-dipyramidal |
mmm |
Vh = D2h |
47: Pmmm, 48: Pnnn, 49: Pccm, 50: Pban, 51: Pmma, 52: Pnna, 53: Pmna, 54: Pcca, 55: Pbam, 56: Pccn, 57: Pbcm, 58: Pnnm, 59: Pmmn, 60: Pbcn, 61: Pbca, 62: Pnma 63: Cmcm, 64: Cmce, 65: Cmmm, 66: Cccm, 67: Cmme, 68: Ccce, 69: Fmmm, 70: Fddd, 71: Immm, 72: Ibam, 73: Ibca, 74: Imma |
3 |
- |
- |
- |
3 |
y |
47: YBa2Cu3O7-x |
8 |
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Crystal system |
Crystal Class |
2-fold axes |
3-fold axes |
4-fold axes |
6-fold axes |
mirror planes |
inversion |
Examples |
Number of symmetry elements |
Generating matrices |
rank 1 tensors1 |
rank 2 symmetric tensors2 |
rank 2 asymmetric tensors |
rank 3 tensors3 |
rank 4 tensors |
Group elements | |||
tetragonal-pyramidal |
4 |
C4 |
75: P4, 76: P41, 77: P42, 78: P43, 79: I4, 80: I41 |
- |
- |
1 |
- |
- |
n |
|
4 |
||||||||
tetragonal-disphenoidal |
4 |
S4 |
81: P4, 82: I4 |
1 |
- |
- |
- |
- |
n |
|
4 |
||||||||
tetragonal-dipyramidal |
$\frac{4}{m}$ |
C4h |
83: P4/m, 84: P42/m, 85: P4/n, 86: P42/n, 87: I4/m, 88: I41/a |
- |
- |
1 |
- |
1 |
y |
|
8 |
||||||||
tetragonal-trapezoidal |
422 |
D4 |
89: P422, 90: P4212, 91: P4122, 92: P41212, 93: P4222, 94: P42212, 95: P4322, 96: P43212, 97: I422, 98: I4122 |
4 |
- |
1 |
- |
- |
n |
|
8 |
||||||||
ditetragonal-pyramidal |
4mm |
C4v |
99: P4mm, 100: P4bm, 101: P42cm, 102: P42nm, 103: P4cc, 104: P4nc, 105: P42mc, 106: P42bc, 107: I4mm, 108: I4cm, 109: I41md, 110: I41cd |
- |
- |
- |
- |
4 |
n |
99: PZT PbZrxTi1-xO3 x<0.52 |
8 |
||||||||
tetragonal-scalenoidal |
42m |
Vd = D2d |
111: P42m, 112: P42c, 113: P421m, 114: P421c, 115: P4m2, 116: P4c2, 117: P4b2, 118: P4n2, 119: I4m2, 120: I4c2, 121: I42m, 122: I42d |
3 |
- |
- |
- |
2 |
n |
|
8 |
||||||||
ditetragonal-dipyramidal |
$\frac{4}{m}mm$ |
D4h |
123: P4/mmm, 124: P4/mcc, 125: P4/nbm, 126: P4/nnc, 127: P4/mbm, 128: P4/mnc, 129: P4/nmm, 130: P4/ncc, 131: P42/mmc, 132: P42/mcm, 133: P42/nbc, 134: P42/nnm, 135: P42/mbc, 136: P42/mnm, 137: P42/nmc, 138: P42/ncm, 139: I4/mmm, 140: I4/mcm, 141: I41/amd, 142: I41/acd |
4 |
- |
1 |
- |
5 |
y |
123: Tetrataenite, 139: In |
16 |
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Crystal system |
Crystal Class |
2-fold axes |
3-fold axes |
4-fold axes |
6-fold axes |
mirror planes |
inversion |
Examples |
Number of symmetry elements |
Generating matrices |
rank 1 tensors1 |
rank 2 symmetric tensors2 |
rank 2 asymmetric tensors |
rank 3 tensors3 |
rank 4 tensors |
Group elements | |||
trigonal-pyramidal |
3 |
C3 |
143: P3, 144: P31, 145: P32, 146: R3 |
- |
1 |
- |
- |
- |
n |
|
3 |
||||||||
rhombohedral |
3 |
S6 = C6i |
147: P3, 148: R3 |
- |
1 |
- |
- |
- |
y |
|
6 |
||||||||
trigonal-trapezoidal |
32 |
D3 |
149: P312, 150: P321, 151: P3112, 152: P3121, 153: P3212, 154: P3221, 155: R32 |
3 |
1 |
- |
- |
- |
n |
154: α-Quartz |
6 |
||||||||
ditrigonal-pyramidal |
3m |
C3v |
156: P3m1, 157: P31m, 158: P3c1, 159: P31c, 160: R3m, 161: R3c |
- |
1 |
- |
- |
3 |
n |
161: ferroelectric LiNbO3 |
6 |
||||||||
ditrigonal-scalahedral |
3m |
D3d |
162: P31m, 163: P31c, 164: P3m1, 165: P3c1, 166: R3m, 167: R3c |
3 |
1 |
- |
- |
3 |
y |
167: calcite, paraelectric LiNbO3, sapphire (α-Al2O3) |
12 |
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Crystal system |
Crystal Class |
2-fold axes |
3-fold axes |
4-fold axes |
6-fold axes |
mirror planes |
inversion |
Examples |
Number of symmetry elements |
Generating matrices |
rank 1 tensors1 |
rank 2 symmetric tensors2 |
rank 2 asymmetric tensors |
rank 3 tensors3 |
rank 4 tensors |
Group elements | |||
hexagonal-pyramidal |
6 |
C6 |
168: P6, 169: P61, 170: P65, 171: P62, 172: P64, 173: P63 |
- |
- |
- |
1 |
- |
n |
6 |
|||||||||
trigonal-dipyramidal |
6 |
C3h = S3 |
174: P6 |
- |
1 |
- |
- |
1 |
n |
6 |
|||||||||
hexagonal-dipyramidal |
$\frac{6}{m}$ |
C6h |
175: P6/m, 176: P63/m |
- |
- |
- |
1 |
1 |
y |
|
12 |
||||||||
hexagonal-trapezoidal |
622 |
D6 |
177: P622, 178: P6122, 179: P6522, 180: P6222, 181: P6422, 182: P6322 |
6 |
- |
- |
1 |
- |
n |
180: β-Quartz |
12 |
||||||||
dihexagonal-pyramidals |
6mm |
C6v |
183: P6mm, 184: P6cc, 185: P63cm, 186: P63mc |
- |
- |
- |
1 |
6 |
n |
186: Wurtzite, |
12 |
||||||||
ditrigonal-dipyramidal |
6m2 |
D3h |
187: P6m2, 188: P6c2, 189: P62m, 190: P62c |
3 |
1 |
-s |
- |
4 |
n |
|
12 |
||||||||
dihexagonal-dipyramidal |
$\frac{6}{m}mm$ |
D6h |
191: P6/mmm, 192: P6/mcc, 193: P63/mcm, 194: P63/mmc |
6 |
- |
- |
1 |
7 |
y |
194: hcp, Mg, Be, Sc, α-Ti, Co, Zn, Y, Zr, Tc, Ru, Cd, Gd, Tb, Dy, Ho, Er, Tm, Lu, Hf, Re, Os, Tl, graphite, MoS2, ice Ih |
24 |
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Crystal system |
Crystal Class |
2-fold axes |
3-fold axes |
4-fold axes |
6-fold axes |
mirror planes |
inversion |
Examples |
Number of symmetry elements |
Generating matrices |
rank 1 tensors1 |
rank 2 symmetric tensors2 |
rank 2 asymmetric tensors |
rank 3 tensors3 |
rank 4 tensors |
Group elements | |||
tetrahedral |
23 |
T |
195: P23, 196: F23, 197: I23, 198: P213, 199: I213 |
3 |
4 |
- |
- |
- |
n |
12 |
|||||||||
diploidal |
m3 |
Th |
200: Pm3, 201: Pn3, 202: Fm3, 203: Fd3, 204: Im3, 205: Pa3, 206: Ia3 |
3 |
4 |
- |
- |
3 |
y |
|
24 |
||||||||
gyroidal |
432 |
O |
207: P432, 208: P4232, 209: F432, 210: F4132, 211: I432, 212: P4332, 213: P4132, 214: I4132 |
6 |
4 |
3 |
- |
- |
n |
|
24 |
||||||||
hextetrahedral |
43m |
Td |
215: P43m, 216: F43m, 217: I43m, 218: P43n, 219: F43c, 220: I43d |
3 |
4 |
- |
- |
6 |
n |
216: Zincblende, GaAs, GaP, InAs, SiC |
24 |
||||||||
hexoctahedral |
m3m |
Oh |
221: Pm3m, 222: Pn3n, 223: Pm3n, 224: Pn3m 225: Fm3m, 226: Fm3c, 227: Fd3m, 228: Fd3c 229: Im3m, 230: Ia3d |
6 |
4 |
3 |
- |
9 |
y |
221: CsCl, cubic perovskite |
48 |
1 Rank 1 tensors are vectors. Examples of properties described by rank 1 tensors are pyroelectricity and pyromagnetism.
2 Rank 2 tensors are matrices. Examples of properties described by rank 2 tensors are electrical conductivity, thermal conductivity, dielectic constant, magnetic susceptibility, and thermal expansion. Only the upper elements of the matrices are given because gij = gji.
3 Examples of properties described by rank 3 tensors are piezoelectricity and piezomagnetism.