Here you see the electron density of a single atom with a Gaussian shape on the left and its diffraction pattern on the right. Copy both of these graphs by clicking the copy buttons above the graphs. Use the shape menu to choose a pseudo atom which has compact core and diffuse valence electrons. Calculate, and then steal data on each of the copied graphs to compare both pairs of plots.
Now choose monatomic crystal from the material menu, reselect pseudo atom from the shape menu, and calculate. The envelope of the diffraction pattern reflects the intensity plot of the single atom.