Dynamical scattering and electron diffraction from thin polymer lamellar crystals - poly(tert-butylethylene sulfide).
Strong violations of Friedel symmetry are observed in hk0 electron diffraction patterns from lamellar crystals of poly(tert-butylethylene sulfide) obtained at 120 kV. These deviations are largely explained by a multislice dynamical scattering calculation based on the crystal structure model. Further improvement is found when a secondary scattering component is added, in keeping with a perfect crystallite thickness less than that of the lamellar thickness. Despite the multiple-scattering perturbations, the frustrated chain packing can still be determined by direct methods followed by Fourier refinement. However, the Friedel-related intensities must be averaged before calculation of normalized structure factors.
Electron Diffraction Department, Hauptman-Woodward Medical Research Institute, 73 High Street, Buffalo, NY 14203-1196, USA. dorset@hwi.buffalo.edu
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Dorset
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Dumas
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Cartier
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Lotz