This important book presents a comprehensive account of the techniques & applications of single crystal neutron diffraction in the area of chemical crystallography & molecular structure. Beginning with a brief description of the general principles & the reasons for choosing the technique - the "why" - the book covers the methods for both the production of neutrons & the measurement of their scattering by molecular crystals - the "how" - followed by a detailed survey of past, present & future applications - the "what". The coverage of both steady state & pulsed neutron sources & instrumentation is extensive, while the survey of applications is the most comprehensive yet undertaken. The book endeavours to show why the technique is an essential method for studying areas as diverse as hydrogen bonding & weak interactions, organometallics, supramolecular chemistry & crystal engineering, metal hydrides, charge density & pharmaceuticals. It is an ideal reference source for the research worker interested in using neutron diffraction to study the structure of molecules. Contents: Crystallography & the Importance of Structural Information; Neutron Scattering; Neutron Diffractometers; Review of Applications I: The Accurate Location of Atoms; Review of Applications II: Hydrogen Bonding & Other Intermolecular Interactions; Review of Applications III: Probing Vibrations & Disorder; Impact on Material Properties & Design; The Future: New Instruments, New Sources, New Techniques. Readership: Students & researchers involved in structural science, especially chemical crystallography.

This important book presents a comprehensive account of the techniques and applications of single crystal neutron diffraction in the area of chemical crystallography and molecular structure. Beginning with a brief description of the general principles and the reasons for choosing the technique — the “why” — the book covers the methods for both the production of neutrons and the measurement of their scattering by molecular crystals — the “how” — followed by a detailed survey of past, present and future applications — the “what”. The coverage of both steady state and pulsed neutron sources and instrumentation is extensive, while the survey of applications is the most comprehensive yet undertaken. The book endeavours to show why the technique is an essential method for studying areas as diverse as hydrogen bonding and weak interactions, organometallics, supramolecular chemistry and crystal engineering, metal hydrides, charge density and pharmaceuticals. It is an ideal reference source for the research worker interested in using neutron diffraction to study the structure of molecules.

X-Ray and Neutron Diffraction describes the developments of the X-ray and the various research done in neutron diffraction. Part I of the book concerns the principles and applications of the X-ray and neutrons through their origins from classical crystallography. The book explains the use of diffraction methods to show the highly regular arrangement of atoms that forms a continuous pattern in three-dimensional space. The text evaluates the limitations and benefits of using the different types of radiation sources, whether these are X-rays, neutrons, or electrons. Part II is a collection of reprints discussing the development of techniques that includes a modification of the Bragg method, which is a method of X-ray crystal analysis. One paper presents an improved numerical method of two-dimensional Fourier synthesis for crystals. This method uses a greatly reduced process of arrangement of sets of figures found in the two-dimensional Fourier series. The book also notes the theoretical considerations and the practical details, and then addresses precautions against possible inclusions of errors in this method. The text deals as well with the magnetic scattering of neutrons, and one paper presents a simple method of gathering information about the magnetic moment of the neutron besides the traditional Stern-Gerlach method. Nuclear scientists and physicists, atomic researchers, and nuclear engineers will greatly appreciate the book.

This book aims to explain how and why the detailed three-dimensional architecture of molecules can be determined by an analysis of the diffraction patterns obtained when X rays or neutrons are scattered by the atoms in single crystals. Part 1 deals with the nature of the crystalline state, diffraction generally, and diffraction by crystals in particular, and, briefly, the experimental procedures that are used. Part II examines the problem of converting the experimentally obtained data into a model of the atomic arrangement that scattered these beams. Part III is concerned with the techniques for refining the approximate structure to the degree warranted by the experimental data. It also describes the many types of information that can be learned by modern crystal structure analysis. There is a glossary of terms used and several appendixes to which most of the mathematical details have been relegated.

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; for 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.

Crystallography may be described as the science of the structure of materi als, using this word in its widest sense, and its ramifications are apparent over a broad front of current scientific endeavor. It is not surprising, therefore, to find that most universities offer some aspects of crystallography in their undergraduate courses in the physical sciences. It is the principal aim of this book to present an introduction to structure determination by X-ray crystal lography that is appropriate mainly to both final-year undergraduate studies in crystallography, chemistry, and chemical physics, and introductory post graduate work in this area of crystallography. We believe that the book will be of interest in other disciplines, such as physics, metallurgy, biochemistry, and geology, where crystallography has an important part to play. In the space of one book, it is not possible either to cover all aspects of crystallography or to treat all the subject matter completely rigorously. In particular, certain mathematical results are assumed in order that their applications may be discussed. At the end of each chapter, a short bibliog raphy is given, which may be used to extend the scope of the treatment given here. In addition, reference is made in the text to specific sources of information. We have chosen not to discuss experimental methods extensively, as we consider that this aspect of crystallography is best learned through practical experience, but an attempt has been made to simulate the interpretive side of experimental crystallography in both examples and exercises.