xnd top | Next file | Previous file |
---|
Bravais | extinction rule |
P | |
---|---|
A | k + l = 2n |
B | h + l = 2n |
C | h + k = 2n |
I | h + k + l = 2n |
F | k + l = 2n, h + l = 2n, (h + k = 2n) |
R | h - k + l = 3n |
S | k - h + l = 3n |
H | h - kl = 3n |
q_x | q_y | q_z | 3D lattice | extinction rule | listing code | |
---|---|---|---|---|---|---|
0 | 0 | 0 | all | using 3D rules | ||
1/2 | 0 | 0 | P | h + m = 2n | A4P | |
A | h + m = 2n, k + l = 2n | A4A | ||||
0 | 1/2 | 0 | P | k + m = 2n | B4P | |
B | k + m = 2n, h + l = 2n | B4B | ||||
0 | 0 | 1/2 | P | l + m = 2n | C4P | |
C | l + m = 2n, h + k = 2n | C4C | ||||
0 | 1/2 | 1/2 | orthorhombic | k + m = 2n, l + m = 2n | U4O | |
tetragonal | k + l + m = 2n | U4Q | ||||
1/2 | 0 | 1/2 | orthorhombic | h + m = 2n, l + m = 2n | V4O | |
tetragonal | h + l + m = 2n | V4Q | ||||
1/2 | 1/2 | 0 | orthorhombic | h + m = 2n, k + m = 2n | W4O | |
tetragonal | h + k + m = 2n | W4Q | ||||
1 | 0 | 0 | P | L4P | ||
A | k + l = 2n | L4A | * | |||
B | h + l + m = 2n | L4B | ||||
C | h + k + m = 2n | L4C | ||||
I | h + k + l + m = 2n | L4I | ||||
F | h + k + m = 2n, k + l = 2n | L4F | ||||
0 | 1 | 0 | P | M4P | ||
A | k + l + m = 2n | M4A | ||||
B | h + l = 2n | M4B | * | |||
C | h + k + m = 2n | M4C | ||||
I | h + k + l + m = 2n | M4I | ||||
F | h + k + m = 2n, h + l = 2n | M4F | ||||
0 | 0 | 1 | P | N4P | ||
A | k + l + m = 2n | N4A | ||||
B | h + l + m = 2n | N4B | ||||
C | h + k = 2n | N4C | * | |||
I | h + k + l + m = 2n | N4I | ||||
F | h + k = 2n, k + l + m = 2n | N4F | ||||
1 | 1 | 0 | P | LM4P | ||
A | k + l + m = 2n | LM4A | ||||
B | h + l + m = 2n | LM4B | ||||
C | h + k = 2n | LM4C | + | |||
I | h + k + l = 2n | LM4I | + | |||
F | h + k = 2n, k + l + m = 2n | LM4F | ||||
0 | 1 | 1 | P | MN4P | ||
A | k + l = 2n | MN4A | ||||
B | h + l + m = 2n | MN4B | ||||
C | h + k + m = 2n | MN4C | ||||
I | h + k + l + m = 2n | MN4I | ||||
F | h + k + m = 2n, k + l = 2n | MN4F | ||||
1 | 0 | 1 | P | LN4P | ||
A | k + l = 2n | LN4A | ||||
B | h + l + m = 2n | LN4B | ||||
C | h + k + m = 2n | LN4C | ||||
I | h + k + l + m = 2n | LN4I | ||||
F | h + k + m = 2n, k + l = 2n | LN4F | ||||
1/3 | 1/3 | 0 | R | h - k + m = 3n | R4 |
As it can be seen in the upper table, the case of rational components (1/2,1/2,0) generates
two kind of 4D extinction which are not related directly to the 3D Bravais lattice but to
the symmetry of this lattice (tetragonal or orthorhombic). Some cases (*) have been
generated for encoding reasons but are not associated with real crystallographic cases; the cases(+)
are associated with non classical settings.
The systematic relation between the rational part of q and the 4D extinction setting was
introduced in xnd by D. Grebille (ISMRA, Caen) and coll. as an efficient way to describe
the extinction rules for 4D structure. This seems to have been a reasonable choice as no
standard name remains for 4D Bravais lattice.
xnd top | Next file | Previous file |
---|