Interactive Tutorial about Diffraction Modification I: Original structure 

Modification
Goto 
The structure chosen for this set of examples is an artificial structure in
the space group Pnnn. The lattice constants have been chosen as
7.5, 10 and 12.5 Angstroem with the asymmetric unit given in the table below.
A simple projection of the structure along [001] is shown in the following
image (one unit cell). The grid gives 0.25 intervals in fractional
coordinates. The origin of the unit cell is at the lower left corner, the
horizontal axis is [100], the vertical axis [010]. Click on the picture
to get a full screen version of it.
The following pictures show the Fourier transform of a single unit cell and the intensity distribution of a crystal. The left picture shows the hk0 layer of reciprocal space. The image corresponds to the Fourier transform of a single unit cell. The intensity distribution of the crystal is shown as blue dots marking the Bragg reflections. The next two images show the intensity along the lines from 0,0,0 to 8.5,0,0 and from 0,0,0 to 0,8.5,0. Note that the intensity is zero at all integer h00, h=2n+1 and 0k0, k=2n+1. Additionally, the intensity at 0,4,0 is (almost) zero as well. The blue curve is again the Fourier transform of a single unit cell and the red line is the Fourier transform of the crystal. The vertical scale has been cut off at approximately 40% of the intensity at 0,0,0. Click on the pictures to get a full screen image.
The students can learn the following based on the observations made so far:


© Th. Proffen and R.B. Neder, 2003 