Origin on mm2

Asymmetric unit

0 ≤ x ≤ 1/4; 0 ≤ y ≤ 1/2

For (0, 0, 0)+ set

(1)  1

(2)  2   0, 0, z

(3)  m   x, 0, z

(4)  m   0, y, z

For (1/2, 1/2, 0)+ set

(1)  t(1/2, 1/2, 0)

(2)  2   1/4, 1/4, z

(3)  a   x, 1/4, z

(4)  b   1/4, y, z

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

Positions

Multiplicity, Wyckoff letter, Site symmetry	Coordinates	Reflection conditions
	(0, 0, 0)+  (1/2, 1/2, 0)+	General:
8 f 1	(1) x, y, z (2) -x, -y, z (3) x, -y, z (4) -x, y, z	hk: h + k = 2n 0k: k = 2n h0: h = 2n

		Special: as above, plus
4 e  m . .	0, y, z 0, -y, z	no extra conditions
4 d  . m .	x, 0, z -x, 0, z	no extra conditions
4 c  . . 2	1/4, 1/4, z 1/4, 3/4, z	hk: h = 2n
2 b  m m 2	0, 1/2, z	no extra conditions
2 a  m m 2	0, 0, z	no extra conditions

Symmetry of special projections

Along [001]   c2mm a' = a   b' = b    Origin at 0, 0, z

Along [100]   1m1 a' = 1/2b    Origin at x, 0, 0

Along [010]   1m1 a' = 1/2a    Origin at 0, y, 0

Maximal non-isotypic subgroups

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I	[2] c1m1 (cm11, 13)	(1; 3)+
	[2] cm11 (13)	(1; 4)+
	[2] c112 (p112, 3)	(1; 2)+

IIa	[2] pba2 (25)	1; 2; (3; 4) + (1/2, 1/2, 0)
	[2] pbm2 (pma2, 24)	1; 3; (2; 4) + (1/2, 1/2, 0)
	[2] pma2 (24)	1; 4; (2; 3) + (1/2, 1/2, 0)
	[2] pmm2 (23)	1; 2; 3; 4

IIb

none

Maximal isotypic subgroups of lowest index

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IIc	[3] cmm2 (a' = 3a or b' = 3b) (26)

Minimal non-isotypic supergroups

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I	[2] cmmm (47); [2] cmme (48); [2] p4mm (55); [2] p4bm (56); [2] p-42m (57); [2] p-421m (58); [3] p6mm (77)

II	[2] pmm2 (a' = 1/2a, b' = 1/2b) (23)

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