Solid State Chemistry and its Applications. Anthony R. West
Чтение книги онлайн.
Читать онлайн книгу Solid State Chemistry and its Applications - Anthony R. West страница 70
Figure 1.65 Orthorhombic space group F222 (No 22); coordinates of equivalent positions 16(k)
Special positions with point symmetry 222, 4(a): only one position is given as the other three are generated by the face centring; 0, 0, 0; 4(b): 0, 0, ½; 4(c):
There are sixteen general equivalent positions that fall into four groups related by the face‐centring condition. The four sets are related as (0, 0, 0); (½, ½, 0); (½, 0, ½) and (0, ½, ½). Thus, position l, (x, y, z), is related to positions 2–4: (x + ½, у + ½, z); (x + ½, y, z + ½) and (x, y + ½, z + ½). Generation of the remaining equivalent positions by the action of the 2‐fold axes should be straightforward.
1.18.5.6 Tetragonal I41
The principal axis in the space group I41, Fig. 1.66, is a 41 screw axis parallel to z. There are four such axes which intersect the unit cell at x =
Figure 1.66 Tetragonal space group I41 (No 80); coordinates of equivalent positions 8(b):
Special positions with point symmetry 2, 4(a): 0, 0, z; 0, ½,