The basis has one atom A at the origin and one atom
1
B at a.
2
The single Laue equation
defines a set of parallel planes in Fourier space. Intersections with a sphere are
a set of circles, so that the diffracted beams lie on a set of cones. (b) S(n) = f
a k ⋅ ∆ = 2π× (integer)
A + fB e–iπn
. For n odd, S = fA –
2-2 f
B; for n even, S = fA + fB. (c) If fA = fB the atoms diffract identically, as if the primitive translation vector
were
1
a
2
and the diffraction condition
1
( ) 2 (integer)