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Title: SINGLE CRYSTAL NEUTRON DIFFRACTION.

Single-crystal neutron diffraction measures the elastic Bragg reflection intensities from crystals of a material, the structure of which is the subject of investigation. A single crystal is placed in a beam of neutrons produced at a nuclear reactor or at a proton accelerator-based spallation source. Single-crystal diffraction measurements are commonly made at thermal neutron beam energies, which correspond to neutron wavelengths in the neighborhood of 1 Angstrom. For high-resolution studies requiring shorter wavelengths (ca. 0.3-0.8 Angstroms), a pulsed spallation source or a high-temperature moderator (a ''hot source'') at a reactor may be used. When complex structures with large unit-cell repeats are under investigation, as is the case in structural biology, a cryogenic-temperature moderator (a ''cold source'') may be employed to obtain longer neutron wavelengths (ca. 4-10 Angstroms). A single-crystal neutron diffraction analysis will determine the crystal structure of the material, typically including its unit cell and space group, the positions of the atomic nuclei and their mean-square displacements, and relevant site occupancies. Because the neutron possesses a magnetic moment, the magnetic structure of the material can be determined as well, from the magnetic contribution to the Bragg intensities. This latter aspect falls beyond the scope of the present unit; formore » information on magnetic scattering of neutrons see Unit 14.3. Instruments for single-crystal diffraction (single-crystal diffractometers or SCDs) are generally available at the major neutron scattering center facilities. Beam time on many of these instruments is available through a proposal mechanism. A listing of neutron SCD instruments and their corresponding facility contacts is included in an appendix accompanying this unit.« less
Authors:
Publication Date:
OSTI Identifier:
777867
Report Number(s):
BNL--68112; KC030201
R&D Project: CO09; KC030201; TRN: AH200118%%508
DOE Contract Number:
AC02-98CH10886
Resource Type:
Book
Resource Relation:
Other Information: PBD: 13 Mar 2001
Publisher:
Brookhaven National Laboratory, Upton, NY (US)
Research Org:
Brookhaven National Lab., Upton, NY (US)
Sponsoring Org:
USDOE Office of Energy Research (ER) (US)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BRAGG REFLECTION; CRYSTAL STRUCTURE; DIFFRACTION; MAGNETIC MOMENTS; MONOCRYSTALS; NEUTRON DIFFRACTION; NEUTRONS; SPACE GROUPS; THERMAL NEUTRONS