Electron microscopy
 
P63/mmc (194) space group
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Table 3026a. P63/mmc (194) space group.

Name in the International Tables for Crystallography
P63/mmc P
191 6/mmm
Crystal system
Hexagonal (HCP) 6/mmm
24 1, √(4/3), √(4/R2), √(4/3+1/R2), √(4/3+4/R2), √4, ... (R=1.6)
Asymm
0≤ x ≤ 2/3 and 0 ≤ y ≤ 2/3 and 0 ≤ z ≤ 1/4 and x ≤ 2 y and y ≤ min(1-x,2 x)
Symmetry (atomic coordinates)
X, Y, Z; -Y, X-Y, Z; Y-X, -X, Z; -X, -Y, 1/2+Z; Y, Y-X, 1/2+Z; X-Y, X, 1/2+Z; Y, X, -Z; X-Y, -Y, -Z; -X, Y-X, -Z; -Y, -X, 1/2-Z; Y-X, Y, 1/2-Z; X, X-Y, 1/2-Z; -X, -Y, -Z; Y, Y-X, -Z; X-Y, X, -Z; X, Y, 1/2-Z; Y-X, -X, 1/2-Z; -Y, X-Y, 1/2-Z; -Y, -X, Z; Y-X, Y, Z; X, X-Y, Z; Y, X, 1/2+Z; X-Y, -Y, 1/2+Z; -X, Y-X, 1/2+Z.
0001:1 = 2n; hkil: none; hh2hl: 1 = 2n; hh01: none
Crystal examples
MgZn2: 2 Zn at 0, 0, 0 and 0, 0, 1/2; 4 Mg at 1/3, 2/3, z; 2/3, 1/3, z + 1/2; 2/3, 1/3, -z and 1/3, 2/3, -z + 1/2; 6 Zn at x, 2x, 1/4; -2x, -x, 1/4; x, -x, 1/4 and -x, -2x, 3/4.

Table 3026b. Lattice constants of typical structures with P63/mmc (194).

Structure
a (nm)
b (nm)
General
2r (r is metallic radius) (8/3)1/2 a
Be
0.2286 0.3583
Cd
0.2979 0.5617
Mg
0.3209 0.5211
Os
0.2735 0.4319
Re
0.2760 0.4458
Ru
0.2706 0.4282
Ti
0.2506 0.4679
Zn
0.2665 0.4947
Zr
0.3312 0.5148

63 screw axis

Figure 3026. 63 screw axis.

 

 

 

 

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