Precession Electron Diffraction (PED) offers a number of advantages for
crystal structure analysis and solving unknown structures using electron
diffraction. The current article uses many-beam simulations of PED intensities,
in combination with model structures, to arrive at a better understanding of
how PED differs from standard unprecessed electron diffraction. It is shown
that precession reduces the chaotic oscillatory behavior of electron
diffraction intensities as a function of thickness. An additional
characteristic of PED which is revealed by simulations is reduced sensitivity
to structure factor phases. This is shown to be a general feature of dynami-cal
intensities collected under conditions in which patterns with multiple incident
beam orienta-tions are averaged together. A new and significantly faster method
is demonstrated for dynami-cal calculations of PED intensities, based on using
information contained in off-central columns of the scattering matrix.Comment: 20 pages, 7 Figure