[script p]ccm mmm Orthorhombic
No. 21 [script p]2/c2/c2/m Patterson symmetry [script p]mmm

symmetry group diagram

Origin at centre (2/m) at cc2/m

Asymmetric unit 0 ≤ x; 0 ≤ y; 0 ≤ z ≤ 1/2

Symmetry operations

(1)  1   (2)  2   0, 0, z(3)  2   0, y, 1/4(4)  2   x, 0, 1/4
(5)  -1   0, 0, 0(6)  m   x, y, 0(7)  c   x, 0, z(8)  c   0, y, z

Generators selected (1); t(0, 0, 1); (2); (3); (5)

Positions

Multiplicity, Wyckoff letter,
Site symmetry		 Coordinates Reflection conditions
 General:
8 g 1
(1) x, y, z(2) -x, -y, z(3) -x, y, -z + 1/2(4) x, -y, -z + 1/2
(5) -x, -y, -z(6) x, y, -z(7) x, -y, z + 1/2(8) -x, y, z + 1/2
l: l = 2n
  Special: no extra conditions
4 f  . . m 
x, y, 0-x, -y, 0-x, y, 1/2x, -y, 1/2
4 e  . . 2 
0, 0, z0, 0, -z + 1/20, 0, -z0, 0, z + 1/2
4 d  . 2 . 
0, y, 1/40, -y, 1/40, -y, 3/40, y, 3/4
4 c  2 . . 
x, 0, 1/4-x, 0, 1/4-x, 0, 3/4x, 0, 3/4
2 b  2 2 2 
0, 0, 1/40, 0, 3/4
2 a  . . 2/m 
0, 0, 00, 0, 1/2

Symmetry of special projections

Along [001]   2mm

Origin at 0, 0, z 		Along [100]   [script p]2mm
a' = 1/2c   
Origin at x, 0, 0 		Along [010]   [script p]2mm
a' = 1/2c   
Origin at 0, y, 0

Maximal non-isotypic non-enantiomorphic subgroups

I[2] [script p]c2m ([script p]2cm, 19)1; 3; 6; 8
 [2] [script p]2cm (19)1; 4; 6; 7
 [2] [script p]cc2 (16)1; 2; 7; 8
 [2] [script p]222 (13)1; 2; 3; 4
 [2] [script p]112/m (11)1; 2; 5; 6
 [2] [script p]12/c1 ([script p]2/c11, 7)1; 3; 5; 7
 [2] [script p]2/c11 (7)1; 4; 5; 8
IIa none
IIbnone

Maximal isotypic subgroups and enantiomorphic subgroups of lowest index

IIc[3] [script p]ccm (c' = 3c) (21)

Minimal non-isotypic non-enantiomorphic supergroups

I[2] [script p]4/mcc (40); [2] [script p]42/mmc (41); [3] [script p]6/mcc (74)
II[2] [script p]mmm (c' = 1/2c) (20)








































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