Bloch wave symmetries in electron diffraction: Applications to Friedels law, Gjonnes–Moodie lines and refraction at interfaces

We classify the point symmetries at the different points in the Brillouin zone for the 17 two-dimensional space groups and the symmetries of the Bloch waves for the 10 two-dimensional crystallographic point groups. Simple examples involving breakdown of Friedels law, Gjonnes–Moodie lines, and reflection and refraction at interfaces are presented.