CONTINUED No. 131 P4
2
/mmc
Generators selected (1); t(1, 0,0); t(0,1,0); t(0,0,1); (2); (3); (5); (9)
Positions
Multiplicity,
Wyckoff letter,
Site symmetry
Coordinates Reflection conditions
General:
16 r 1(1)x,y,z (2) ¯x, ¯y,z (3) ¯y,x,z +
1
2
(4) y, ¯x, z +
1
2
(5) ¯x,y, ¯z (6) x, ¯y, ¯z (7) y, x, ¯z +
1
2
(8) ¯y, ¯x, ¯z +
1
2
(9) ¯x, ¯y, ¯z (10) x, y, ¯z (11) y, ¯x, ¯z +
1
2
(12) ¯y,x, ¯z +
1
2
(13) x, ¯y,z (14) ¯x,y,z (15) ¯y, ¯x,z +
1
2
(16) y,x , z +
1
2
hhl : l = 2n
00l : l = 2n
Special: as above, plus
8 qm.. x,y,0¯x, ¯y,0¯y,x,
1
2
y, ¯x,
1
2
¯x,y,0 x , ¯y, 0 y,x,
1
2
¯y, ¯x,
1
2
no extra conditions
8 p . m .
1
2
,y,z
1
2
, ¯y, z ¯y,
1
2
,z +
1
2
y,
1
2
,z +
1
2
1
2
,y, ¯z
1
2
, ¯y, ¯zy,
1
2
, ¯z +
1
2
¯y,
1
2
, ¯z +
1
2
no extra conditions
8 o . m . 0,y,z 0, ¯y,z ¯y, 0,z +
1
2
y, 0,z +
1
2
0,y, ¯z 0, ¯y, ¯zy,0, ¯z +
1
2
¯y,0, ¯z +
1
2
no extra conditions
8 n ..2 x,x,
1
4
¯x, ¯x,
1
4
¯x,x,
3
4
x, ¯x,
3
4
¯x, ¯x,
3
4
x,x,
3
4
x, ¯x,
1
4
¯x,x,
1
4
hkl : l = 2n
4 mm2 m. x,
1
2
,0¯x,
1
2
,0
1
2
,x,
1
2
1
2
, ¯x,
1
2
no extra conditions
4 lm2 m. x,0,
1
2
¯x,0,
1
2
0,x, 00, ¯x,0 no extra conditions
4 km2 m. x,
1
2
,
1
2
¯x,
1
2
,
1
2
1
2
,x,0
1
2
, ¯x, 0 no extra conditions
4 jm2 m. x, 0,0¯x,0,00,x,
1
2
0, ¯x,
1
2
no extra conditions
4 i 2 mm. 0,
1
2
,z
1
2
,0, z +
1
2
0,
1
2
, ¯z
1
2
,0, ¯z +
1
2
hkl : h + k + l = 2n
4 h 2 mm.
1
2
,
1
2
,z
1
2
,
1
2
,z +
1
2
1
2
,
1
2
, ¯z
1
2
,
1
2
, ¯z +
1
2
hkl : l = 2n
4 g 2 mm. 0,0, z 0,0,z +
1
2
0,0, ¯z 0,0 , ¯z +
1
2
hkl : l = 2n
2 f
¯
4 m 2
1
2
,
1
2
,
1
4
1
2
,
1
2
,
3
4
hkl : l = 2n
2 e
¯
4 m 20,0,
1
4
0,0,
3
4
hkl : l = 2n
2 dmmm. 0,
1
2
,
1
2
1
2
,0, 0 hkl : h + k + l = 2n
2 cmmm. 0,
1
2
,0
1
2
,0,
1
2
hkl : h + k + l = 2n
2 bmmm.
1
2
,
1
2
,0
1
2
,
1
2
,
1
2
hkl : l = 2n
2 ammm. 0,0, 00,0,
1
2
hkl : l = 2n
Symmetry of special projections
Along [001] p4mm
a
= ab
= b
Origin at 0,0,z
Along [100] p2mm
a
= bb
= c
Origin at x,0,0
Along [110] p2mm
a
=
1
2
(−a + b) b
=
1
2
c
Origin at x,x , 0
(Continued on preceding page)
455