3. Dynamic interactions between fast electrons and matter

In X-ray and neutron diffraction, kinematic theory applies. Diffraction generally takes place in a single diffracted direction, exactly under Bragg conditions, and the diffracted intensity is proportional to the square of the absorption-corrected structure factor. Electron diffraction is multiple, due to the softening of Bragg conditions, and the diffracted and transmitted beams are coupled. The conditions are dynamic, and the complex diffracted and transmitted amplitudes obtained by solving the dynamic equations are not simply related to electronic structure factors. We will briefly introduce this theory by showing the singularity associated with the diffraction of fast, high-energy electrons.

Several calculation methods have been proposed, with one essential and common approximation: small-angle diffraction [4]