104
8 • Utilisation des tables internationales
1 CONTINUED
N ◦ 28
Pma2
2 Generators selected
(1) ;
t(1, 0, 0) ; t(0, 1, 0) ; t(0, 0, 1) ; (2) ;
(3)
3 Positions
Multiplicity,
Wyckoff letter,
Site symmetry
Coordinates
Reflection conditions
General :
4 d 1
(1) x, y, z (2) x, y, z (3) x + ½, y, z (4) x + ½, y, z h01 : h = 2n
h00 : h = 2n
Special : as above plus
2 c m..
¼, y, z
¾, y, z
no extra condition
2 b ..2
0, ½, z
½, ½, z
hkl : h = 2n
2 a ..2
0, 0, z
½, 0, z
hkl : h = 2n
4 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 = ½ a
Origin at 0, y, 0
5 Maximal non-isomorphic subgroup
I
[2]P112(P2) 1 ;2
[2]P1a1(Pc)
1 ;3
[2]Pm11(Pm) 1 ;4
IIa
none
IIb
[2]Pba2 (b = 2b) [2]Pnm2 1 (c = 2c) ; [2]Pca2 (c = 2c)(Pcn2) ;
[2]Ama2 (b = 2b, c = 2c) ; [2]Aba2 (b = 2b, c = 2c)
6 Maximal isomorphic subgroups of lowaest index
IIc
[2]Pma2 (a = 3a) ; [2]Pma2 (b = 2b) ; [2]Pma2 (c = 2c)
7 Minimal non-isomorphic supergroups
I
[2]Pccm ; [2]Pmma ; [2]Pmna ; [2]Pbcm
II
[2]Ama2 ; [2]Bma2 (Abma2) ; [2]Cmm2 ; [2]Ima2 ; [2Pmm2] (2a = a)
D’après les Tables internationales de cristallographie
Reproduction autorisée par « Kluwer Academic Publishers »
1 En-tête simplifié.