In this first example we calculate the Fourier transform of a single silicon atom. The scattering factors for X-rays are used. The atom is shown schematically as a disk.
Later examples show the actual electron density distribution.
The pictures below show the single atom and the corresponding 1D and 2D Fourier transform. Remember that you can get a full screen version of the pictures by clicking on them. The middle image shows a one dimensional cut through the center of reciprocal space. You can see that the intensity drops off continuously with increasing scattering vector. This is caused by the finite size of the electron density distribution at the atom.