Pair of atoms
Row of atoms
1D crystal builder
Polygons of atoms
This example shall illustrate the different 'scans' in reciprocal
space and allows you to see the path a THETA-scan and a H-scan
follows. All scattering patterns so far have been along H,K or L in
reciprocal space. On a laboratory diffractometer, usually THETA scans
are carried out The construction you are about to see is known to
crystallographers as Ewald sphere.
Here are a few questions to explore:
- Recall the scattering vector diagram presented in the
lecture when discussing the case of two electrons. The
scattering process is illustrated on the right.
- When executing this example you will see a plot that
shows the 2D scattering intensity in the hk plane.
The blue circle shows the
path for the THETA scan which can be seen as
blue graph. The thick green
line shows the scan DISCUS presented, again shown
as green graph. Both result from
the same basic pattern ! Just hit RUN and see for yourself ..
- Now start changing the distance and orientation (within the
xy-plane) of the electron pair and describe their influence.
- Finally investigate the effect of the wavelength of the
X-rays. Typical values used in laboratory sources are
Mo=0.71 A, Cu=1.54 A and Ag=0.55 A.