Interpretation of electron diffraction data from organic microcrystals: a theoretical perspective.
The current framework for the quantitative analysis of transmission electron diffraction data from organic microcrystals is discussed. The appropriate formulation depends upon the crystal perfection: solution-grown material tends to be nearly perfect with regular elastic bends whilst the epitaxial samples are usually considerably less perfect with highly irregular bends. It is possible to obtain Bragg intensity data which are near-kinematical and thus amenable to ab initio structure analysis. Thereafter, the further refinement of the model proceeds with a consideration of dynamical and crystal bending effects. If both of these are small it is a good approximation to analyse them independently rather than use the correct description of dynamical scattering from a deformed foil. The analysis of three-dimensional data sets from tilt series is considered. Although the technique has been successfully demonstrated in several instances there are still details of the analysis that need further clarification.
Dynamical electron diffraction from elastically bent organic crystals
Calculation of dynamical structure factors from a periodically curved crystal lattice have been carried out for the paraffin n-hexatriacontane, C36H74, and the linear polymer anhydrous nigeran, poly[(1 → 3)-α-d- maltose], (C12H20O10)n. These are compared to dynamical structure factors from a fiat crystal, and also to kinematic structure amplitudes from a bent lattice in order to determine the validity of considering each experimentally observed data perturbation separately. Individual treatment of these effects is found to be a good approximation so long as the crystal thickness and bend deformations are each small.
Electron Microscopy, 1972
London: The Institute of Physics 1972 Conf. Series No 14 pp 683 price £15 This volume consists of about 300 papers presented at the 1972 EMCON European Regional Conference on Electron Microscopy held in Manchester. Since the reviewer was a contributor this review cannot be entirely disinterested!