electrondiffraction

Electron diffraction, also called electrondiffraction, is the scattering of a beam of electrons by a crystal or by molecules, producing interference patterns that reflect the atoms’ arrangement. It follows from the wave–particle duality of matter; electrons have a de Broglie wavelength λ = h/p. For electrons accelerated by voltage V (non-relativistic), p ≈ sqrt(2 m e V) and λ ≈ 12.27 / sqrt(V) angstroms. At higher voltages relativistic corrections are sometimes included.

In crystals, diffraction patterns arise when electron waves scattered by lattice planes interfere. In transmission electron microscopy (TEM) and related setups, a thin sample yields a diffraction pattern governed by Bragg's law nλ = 2d sin θ. From SAED patterns, lattice spacings, crystal orientation, and phase information can be obtained; Kikuchi patterns from inelastic scattering are also observed.

History and significance: The wave nature of electrons was demonstrated in 1927 by Davisson and Germer, confirming de Broglie’s hypothesis. Since then electron diffraction has become a central tool in crystallography and materials science, used to determine structures of metals, ceramics, and nanomaterials. Gas-phase electron diffraction is used to determine molecular geometries of small molecules.

Limitations: electrons interact strongly with matter, so samples must be thin and experiments are performed under high vacuum. Multiple scattering and beam damage can complicate interpretation. Electron diffraction complements X-ray diffraction, offering high spatial resolution in electron microscopes and sensitivity to light elements.