Neutron Powder Diffraction

Abstract

For many classes of materials, neutron diffraction is the best way to obtain detailed atomic-level structural information. Diffraction experiments on single crystals provide the most precise data, but sufficiently large specimens (>0.1–0.5 mm3) are often not available. Steady development of instrumentation and data analysis techniques, however, has now made it possible to obtain comparably precise structural information from neutron diffraction experiments on powder samples. Such studies have played a prominent role in solid state physics, chemistry, and materials science in recent years. The special capabilities that have contributed to the success of this technique include atomic cross sections that are often favorable for a particular structural problem, high neutron penetrating power, the excellent resolution achieved with state-of-the-art diffractometers, and steadily advancing analysis techniques that facilitate obtaining structural information from a diverse range of polycrystalline materials.As Axe, Pynn, and Hayter note in their introductory article in this issue of the MRS BULLETIN, atomic scattering cross sections for neutrons are not simply a function of atomic number, as is the case for x-rays. The scattering is predominantly from the nuclei (thus avoiding the form factor diminution observed for x-ray scattering), and coherent neutron scattering cross sections can, generally, be as large for light atoms as for heavy atoms. Light atoms, such as hydrogen (deuterium), oxygen, nitrogen, carbon, or lithium, can therefore be located in the presence of heavier atoms. This advantage has led to the widespread use of neutron powder diffraction for studing metal hydrides and, more recently, oxide superconductors.

Zeolitic and layered materials

“…Jorgensen et al 96 have recently reviewed the use of neutron powder diffraction techniques for studies of inorganic materials including light atom systems, magnetic materials, phase transitions, and in situ studies. An example of use of powder neutron diffraction experiments for the determination of binding sites of adsorbates like benzene in dehydrated potas-sium L zeolite is given in Figure 48 from research of Newsam.97 '98 Neutron diffraction studies of zeolite p is flexible, yielding a change in lattice parameter from 15.1 to about 14 A depending on the type of ion present in the zeolite and specific calcination procedures.…”

Spectroscopy in the Measurements of Acido - Basic Properties of Solids

“…Jorgensen et al [171] have recently reviewed the use of neutron diffraction technique for solids. The use of powder neutron diffraction experiments for the determination of binding energy of adsorbates like benzene in dehydrated potassium L-zeolite can be obtained from the work of Newsam [172,1731.…”