Origin at intersection of 2 with perpendicular plane containing 2₁ axes

Asymmetric unit

0 ≤ x ≤ 1/2; 0 ≤ y ≤ 1/2

(1)  1

(2)  2   0, 0, z

(3)  2(0, 1/2, 0)   1/4, y, 0

(4)  2(1/2, 0, 0)   x, 1/4, 0

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

Positions

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

		Special: as above, plus
2 b  . . 2	0, 1/2, z 1/2, 0, -z	hk: h + k = 2n
2 a  . . 2	0, 0, z 1/2, 1/2, -z	hk: h + k = 2n

Symmetry of special projections

Along [001]   p2gg a' = a   b' = b    Origin at 0, 0, z

Along [100]   2mg a' = b    Origin at x, 1/4, 0

Along [010]   2mg a' = a    Origin at 1/4, y, 0

Maximal non-isotypic subgroups

---

I	[2] p1211 (p2111, 9)	1; 3
	[2] p2111 (9)	1; 4
	[2] p112 (3)	1; 2

IIa

none

IIb

none

Maximal isotypic subgroups of lowest index

---

IIc	[3] p21212 (a' = 3a or b' = 3b) (21)

Minimal non-isotypic supergroups

---

I	[2] pbam (44); [2] pmmn (46); [2] p4212 (54); [2] p-421m (58)

II	[2] c222 (22); [2] p2212 (a' = 1/2a) (p2122, 20)

---