If we scatter from a pair of atoms, we see the characteristic two slit interference pattern with an envelope determined by the sizes of the atoms. Copy diffraction to save this graph.
Now select diatomic crystal to assemble a periodic array of atom pairs. Compare the diffraction patterns for the two cases: pair of atoms and diatomic crystal.
NOTE: Because of the discreteness of the Fourier transform the nulls of the interference pattern will appear as clean zeros only if the atom separation is chosen to be {(odd integer)/(even integer)} in units of the lattice constant a.
For the diatomic crystal, "laue" gives you the freedom to define not only the interatomic spacing but also the sizes of each of the atoms and the relative atomic number (the ratio of total electronic charges in the two atoms). Change the ratio ZA/ZB, make a prediction of the consequence, and see if you're right.
To test your skill, look ONLY at the diffraction pattern of "preset 04" and figure out the values of ALL of the system parameters.