Dynamical Effects of High-Energy Diffraction in Non-centrosymmetric Sphalerite, ZnS

In order to study accidental degeneracies of Bloch waves in non-centrosymmetric crystals, many-beam dynamical effects in high-energy electron diffraction from sphalerite F 43m ZnS have been observed. Several critical-voltage effects due to accidental degeneracies, which were created by projected mirror or rotation symmetries, were observed at various crystallographic orientations. Diffraction phenomena very similar to critical-voltage effects were also observed at the non-centrosymmetric projections. These phenomena were discussed using the second Bethe approximation. By the analysis of experimentally measured critical voltages, the structure factors for the 220 and 200 reflections were determined accurately and discussed in terms of the charge rearrangement caused by ionization.