Characteristics of precession electron diffraction intensities from dynamical simulations

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 dynamical intensities collected under conditions in which patterns with multiple incident beam orientations are averaged together. A new and significantly faster method is demonstrated for dynamical calculations of PED intensities, based on using information contained in off-central columns of the scattering matrix.