Neutron diffraction is a crystallography technique that uses neutrons to determine the atomic structure of a material. Crystallography (from the Greek words crystallon = cold drop / frozen drop, with its meaning extending to all solids with some degree of transparency, and graphein = write) is the experimental science of determining the arrangement of atoms in solids. ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ...

Neutrons are particles found in the atomic nucleus. In a nuclear reactor, neutrons can be set free when nuclei decay (fission, radioactivity). All quantum particles can exhibit wave phenomena we typically associate with light or sound. Diffraction is one of these phenomena; it occurs when waves encounter obstacles whose size is comparable with the wavelength. If the wavelength of a quantum particle is short enough, atoms or their nuclei can serve as diffraction obstacles. When neutrons from a reactor are slowed down and selected properly, their wavelength lies near one angstrom (0.1 nanometer), the typical separation between atoms in a solid material. A stylized representation of a lithium atom. ... Core of a nuclear reactor A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate (as opposed to a nuclear explosion, where the chain reaction occurs in a split second). ... An induced nuclear fission event. ... Radioactivity may mean: Look up radioactivity in Wiktionary, the free dictionary. ... The word quantum, pl. ... In particle physics, an elementary particle is a particle of which other, larger particles are composed. ... Diffraction is the bending and spreading of waves when they meet an obstruction. ... The wavelength is the distance between repeating units of a wave pattern. ... An angstrom, angström, or ångström (symbol Å) is a unit of length. ... A nanometre (American spelling: nanometer) is 1. ...

A neutron diffraction measurement requires a neutron source (e.g. a nuclear reactor or spallation source), a target (the material to be studied), and a detector. Other components may be needed to select the desired neutron wavelength. Some parts of the setup may also be movable. Core of a nuclear reactor A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate (as opposed to a nuclear explosion, where the chain reaction occurs in a split second). ... In nuclear physics, spallation is the process in which a heavy nucleus emits a large number of nucleons as a result of being hit by a high-energy proton, thus greatly reducing its atomic weight. ...

Since neutrons are not charged (not a sufficiant condition, see ahead), they do not interact with the electron cloud surrounding the atom (unlike x-ray and electron diffraction; x-rays although not charged but do interact with electron cloud). The neutrons will only interact with the nucleus of the atom. Thus neutron diffracton reveals the atomic structure only, and not charge distribution around the atom (although the two are usually very similar). Properties The electron is a fundamental subatomic particle that carries a negative electric charge. ... This article is in need of attention from an expert on the subject. ...

Neutron diffraction reveals structural details of the target material, which are measured by recording the way in which neutrons are deflected. Neutrons can also change their speed during the scattering experiment; this is used to study the types of vibrations that can occur in the solid. An important difference between neutron and X-ray diffraction is that neutrons are sensitive to magnetic forces in the material. X-ray crystallography is a technique in crystallography in which the pattern produced by the diffraction of x-rays through the closely spaced lattice of atoms in a crystal is recorded and then analyzed to reveal the nature of that lattice. ...

See also

• X-ray diffraction

X-ray crystallography is a technique in crystallography in which the pattern produced by the diffraction of x-rays through the closely spaced lattice of atoms in a crystal is recorded and then analyzed to reveal the nature of that lattice. ...

External links

• Institute of Physics Neutron Scattering Group (accessed Oct. 2005)