Neutron diffraction is a scientific technique used to determine the structure of materials at the atomic level. It is similar to X-ray diffraction, but uses neutrons instead of X-rays. Neutron diffraction is a powerful tool for studying the structures of materials that are difficult to study using other methods, such as those that are opaque or have atoms that are too close together for X-ray diffraction to be effective.
The neutron is a subatomic particle with no electric charge and a mass slightly greater than that of the proton. Unlike the proton, the neutron is unstable outside of an atomic nucleus, and will decay into a proton and an electron if it exists alone. The stability of neutrons within an atomic nucleus allows them to be used in nuclear reactors and nuclear weapons.
Neutron diffraction works by firing a beam of neutrons at a material sample and then measuring the way in which the neutrons scatter off of the atoms in the sample. By analyzing this scattering pattern, scientists can determine the positions of atoms within the material and hence its three-dimensional structure. Neutron diffraction is particularly useful for studying materials that contain hydrogen atoms, as hydrogen has a high scattering cross section for neutrons relative to other elements.
One advantage of neutron diffraction over other techniques (such as X-ray crystallography) is that it does not require crystals in order to work effectively. This means that it can be used to study amorphous materials (such as glasses) which do not have a well-defined crystal structure. In addition, because neutron beams can penetrate thicker samples than X-ray beams without losing intensity, neutron diffraction can be used to study much larger objects than X-ray crystallography can manage. Finally, because neutrons interact more strongly with light elements such as hydrogen than they do with heavier elements, neutron diffraction can provide information about parts of molecules (such as hydrogens) which would otherwise be invisible using other techniques such as X-ray crystallography