Pma2 C2v4 mm2 Orthorhombic info
No. 28 Pma2 Patterson symmetry Pmmm

symmetry group diagram

Origin on 1 a 2

Asymmetric unit 0 ≤ x ≤ 1/4; 0 ≤ y ≤ 1; 0 ≤ z ≤ 1

Symmetry operations

(1)  1   (2)  2   0, 0, z(3)  a   x, 0, z(4)  m   1/4, y, z

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

Positions

Multiplicity, Wyckoff letter,
Site symmetry		 Coordinates Reflection conditions
 General:
4 d 1
(1) x, y, z(2) -x, -y, z(3) x + 1/2, -y, z(4) -x + 1/2, y, z
h0l : h = 2n
h00 : h = 2n
    Special: as above, plus
2 c  m . . 
1/4, y, z 3/4, -y, z
no extra conditions
2 b  . . 2 
0, 1/2, z 1/2, 1/2, z
hkl : h = 2n
2 a  . . 2 
0, 0, z 1/2, 0, z
hkl : h = 2n

Symmetry of special projections

Along [001]   p2mg
a' = a   b' = b   
Origin at 0, 0, z		Along [100]   p1m1
a' = b   b' = c   
Origin at x, 0, 0		Along [010]   p11m
a' = c   b' = 1/2a   
Origin at 0, y, 0

Maximal non-isomorphic subgroups

I [2] P1a1 (Pc, 7)1; 3
  [2] Pm11 (Pm, 6)1; 4
  [2] P112 (P2, 3)1; 2
IIa none
IIb[2] Pba2 (b' = 2b) (32); [2] Pmn21 (c' = 2c) (31); [2] Pcn2 (c' = 2c) (Pnc2, 30); [2] Pca21 (c' = 2c) (29); [2] Aea2 (b' = 2b, c' = 2c) (41); [2] Ama2 (b' = 2b, c' = 2c) (40)

Maximal isomorphic subgroups of lowest index

IIc[2] Pma2 (b' = 2b) (28); [2] Pma2 (c' = 2c) (28); [3] Pma2 (a' = 3a) (28)

Minimal non-isomorphic supergroups

I[2] Pccm (49); [2] Pmma (51); [2] Pmna (53); [2] Pbcm (57)
II[2] Cmm2 (35); [2] Bme2 (Aem2, 39); [2] Ama2 (40); [2] Ima2 (46); [2] Pmm2 (a' = 1/2a) (25)








































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