halo
otherwise
amorphous ring
(rus. гало otherwise аморфное кольцо)
—
luminous ring around an object; optical phenomenon (from Greek χαλοσ “circle”, “disc”; also aura, nimbus, aureole).
Description
Halos are often seen on X-ray and electron diffraction images of amorphous and nanostructured materials because they do not have a long-range order, i.e. the symmetry and ordered structure over arbitrarily large distances that is inherent in solids with regular crystalline structure. Therefore, instead of the dots typical for crystals, the diffraction peaks of X-rays and electron diffraction patterns of nanomaterials and amorphous materials look like blurred concentric rings.
Illustrations
|
Electron
diffraction on an amorphous polymer film. Author: A. V. Garshev, Lomonosov Moscow State University, Department of Materials Science. |
Authors
- Veresov Alexander G.
- Zhuravleva Natalya G.
Sources
- B.K. Vainshtein. Structural electron diffraction (in Russian). — Moscow: AN SSSR, 1956. — 314 p.
- Z. G. Pinsker. Electron diffraction. — Butterworths Scientific Publications, 1953. — 443 pp.