Integral reflection conditions

Conditions de réflexion intégrales (Fr).

Definition

The integral reflections are the general reflection conditions due to the centring of cells. They are given in the table below:

**Integral reflection conditions for centred lattices.**
Reflection condition	Centring type of cell	Centring symbol
None	Primitive	P R (rhombohedral axes)
h + k = 2n	C-face centred	C
k + l = 2n	A-face centred	A
l + h = 2n	B-face centred	B
h + k + l = 2n	body centred	I
h + k, h + l and k + l = 2n or: h, k, l all odd or all even (‘unmixed’)	all-face centred	F
− h + k + l = 3n	rhombohedrally centred, reverse setting	R (hexagonal axes)
h − k + l = 3n	rhombohedrally centred, obverse setting (standard)	R (hexagonal axes)
h − k = 3n	hexagonally centred	H