User:Johnjbarton/Electron Diffraction Sandbox

Figure 1: Selected area diffraction pattern of a twinned austenite crystal in a piece of steel

Electron diffraction refers to both the electron matter wave diffraction phenomenon and its many applications, especially to crystallography.

Like all diffraction, electron diffraction occurs whenever electrons encounter obstacles, such as atoms, a plate with two slits, or wires; when the obstacles have a regular structure, interference among the electron paths create a diffraction pattern. When suitably prepared electrons encounter crystalline solids striking diffraction patterns emerge – see Figure 1; analysis of these patterns provide deep insight into the atomic structure of the solid.

Electron diffraction resembles x-ray and neutron diffraction technologies but with complementary strengths and areas of application. Electron diffraction from atoms occurs due to elastic scattering, when there is no change in the energy of the electrons during their interactions with atoms. The negatively charged electrons are scattered due to Coulomb forces when they interact with both the positively charged atomic core and the negatively charged electrons around the atoms; most of the interaction occurs quite close to the atoms, within about one angstrom. In comparison, x-rays are scattered after interactions with the electron density while neutrons are scattered by the atomic nuclei through the strong nuclear force.

The magnitude of the interaction of the electrons with a material scales as