Crystal Structure Analysis

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.

By choosing an approach that avoids undue emphasis on the mathematics involved, this book gives practical advice on topics such as growing crystals, solving and refining structures, and understanding and using the results.

The purpose of this book is to explain why molecular structure can be determined by single-crystal diffraction of X rays. It is not an account of the practical procedural details, but rather an account of the underlying physical principles, and the kinds of experiments and methods of handling the experimental data that are used.

Anhand verschiedener Beispiele zeigen die Autoren die Bedeutung der Kristallographie für Chemie und Biochemie auf und bieten somit eine gute Zusammenfassung der allgemeinen Prinzipien der Kristallstrukturanalyse. Zum einen sollen Interessierte, die diese Methode nicht selbst durchführen, in die Lage versetzt werden, deren Ergebnisse zu interpretieren. Zum anderen wird dem Leser deutlich gemacht, welche Bedeutung die ungeheure Datenmenge, die sich aus dieser Methode ergibt, einerseits für die Chemie sowie andererseits für die Biochemie hat. Das Buch ist verständlich geschrieben und mit zahlreichen Abbildungen versehen. Durch die Darstellung der Kristallstrukturanalyse im Vergleich zu anderen Methoden ist das Werk auch besonders für fortgeschrittene Studenten geeignet, die sich mit der Kristallographie vertraut machen wollen.

Structure analysis is based on the phenomena of the diffraction of radia tion by materials. In the first ten to twenty years after Laue's discovery, a very complete theory was developed for the diffraction of x-rays and, later, of electrons. This theory led to equations by means of which it was possible to compute the intensity pattern for a given structure. The theory of structure analysis came to mean that of the diffraction of radiation. In 1935, Patterson pointed out a way leading to the solution of the inverse problem: the finding of the structure from a given intensity distribution pattern. At first the conservatism of researchers, and then the war, hampered the de velopment and broad application of the ideas set forth in this work. It was only during the last ten years that all the rich possibilities of the Patterson method - the method of the analysis of the convolution of the electron density - were brought to light and applied in practice.

The advances in and applications of x-ray and neutron crystallography form the essence of this new edition of this classic textbook, while maintaining the overall plan of the book that has been well received in the academic community since the first edition in 1977. X-ray crystallography is a universal tool for studying molecular structure, and the complementary nature of neutron diffraction crystallography permits the location of atomic species in crystals which are not easily revealed by X-ray techniques alone, such as hydrogen atoms or other light atoms in the presence of heavier atoms. Thus, a chapter discussing the practice of neutron diffraction techniques, with examples, broadens the scope of the text in a highly desirable way. As with previous editions, the book contains problems to illustrate the work of each chapter, and detailed solutions are provided. Mathematical procedures related to the material of the main body of the book are not discussed in detail, but are quoted where needed with references to standard mathematical texts. To address the computational aspect of crystallography, the suite of computer programs from the fourth edition has been revised and expanded. The programs enable the reader to participate fully in many of the aspects of x-ray crystallography discussed in the book. In particular, the program system XRAY* is interactive, and enables the reader to follow through, at the monitor screen, the computational techniques involved in single-crystal structure determination, albeit in two dimensions, with the data sets provided. Exercises for students can be found in the book, and solutions are available to instructors.

X-ray diffraction crystallography for powder samples is a well-established and widely used method. It is applied to materials characterization to reveal the atomic scale structure of various substances in a variety of states. The book deals with fundamental properties of X-rays, geometry analysis of crystals, X-ray scattering and diffraction in polycrystalline samples and its application to the determination of the crystal structure. The reciprocal lattice and integrated diffraction intensity from crystals and symmetry analysis of crystals are explained. To learn the method of X-ray diffraction crystallography well and to be able to cope with the given subject, a certain number of exercises is presented in the book to calculate specific values for typical examples. This is particularly important for beginners in X-ray diffraction crystallography. One aim of this book is to offer guidance to solving the problems of 90 typical substances. For further convenience, 100 supplementary exercises are also provided with solutions. Some essential points with basic equations are summarized in each chapter, together with some relevant physical constants and the atomic scattering factors of the elements.