NEUTRON DIFFRACTION

Neutron diffraction supplements X-ray diffraction and is particularly helpful in locating hydrogen atoms.

The average de Broglie wavelength of thermal neutron is 149 pm at room temperature. A beam of thermal electrons, therefore, has a wavelength suitable for the diffraction studies of studies of crystals. An essentially monochromatic beam may be obtained by diffraction from a crystal monochromator that selects a small band of wavelengths from the beam of thermal electrons from a nuclear reactor. This monochromatic beam of neutrons may be scattered from a crystal in such the same way as X-rays. Although the principles of neutron diffraction are similar to those of X-ray diffraction, several complementary technique to that the x-rays diffraction, Whereas X-rays are scattered by fundamental differences between them result in neutron diffraction being a electrons, neutrons are scattered primarily by the nuclei in a crystal. Hence, the atomic scattering factors as do the no dependence on the Bragg scattering angle). This means that neutron diffraction, in scattering factors for X-rays, but, instead, have roughly the same scattering factors (with contrast to X-rays diffraction, is especially useful for accurately locating hydrogen atoms in a crystal structure. For example, in a compound such as uranium hydride, X-ray diffraction can be utilized to determine the uranium coordinates and neutron diffraction the hydrogen coordinates.

Since neutrons possess a magnetic moment by virtue of having a spin of, there is an additional scattering if the compound contains paramagnetic atoms or ions with unpaired electrons. Thus, neutron diffraction has been widely utilized to investigate structures of magnetic materials, such as MnO and Fe3O, in order to determine the arrangements of the atomic magnetic moments in ferromagnetic and antiferromagnetic crystals. Neutron diffraction is thus a specialized adjunct to X-ray diffraction.