Crystal Structure Determination
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Crystal Structure Determination
Author: Werner Massa
language: en
Publisher: Springer Science & Business Media
Release Date: 2013-03-09
To solve a crystal structure means to determine the precise spatial arrangements of all of the atoms in a chemical compound in the crystalline state. This knowledge gives a chemist access to a large range of information, including connectivity, conformation, and accurate bond lengths and angles. In addition, it implies the stoichiometry, the density, the symmetry and the three dimensional packing of the atoms in the solid. Since interatomic distances are in the region of100-300 pm or 1-3 A, 1 microscopy using visible light (wavelength Ä ca. 300-700 nm) is not applicable (Fig. l. l). In 1912, Max von Laue showed that crystals are based on a three dimensionallattice which scatters radiation with a wavelength in the vicinity of interatomic distances, i. e. X -rays with Ä = 50-300 pm. The process bywhich this radiation, without changing its wave length, is converted through interference by the lattice to a vast number of observable "reflections" with characteristic directions in space is called X-ray diffraction. The method by which the directions and the intensities of these reflections are measured, and the ordering of the atoms in the crystal deduced from them, is called X-ray struc ture analysis. The following chapter deals with the lattice properties of crystals, the starting point for the explanation of these interference phenomena. Interatomic distances Crystals . . . . . . . . . .
Structure Determination by X-Ray Crystallography
Author: M. F. C. Ladd
language: en
Publisher: Springer Science & Business Media
Release Date: 2012-12-06
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.
Theories and Techniques of Crystal Structure Determination
Author: Uri Shmueli
language: en
Publisher: International Union of Crystal
Release Date: 2007-06-07
This concise book is for chemists, material scientists, and physicists who deal with description of crystalline matter and the determination of its structure, and would like to gain more understanding of the principles involved. The main purpose of the book is to introduce the reader to principles of crystallographic symmetry, to discuss some traditional, as well as modern, experimental techniques, to formulate the phase problem of crystallography, and present in some detail themethods for its indirect and direct solution which are indispensable for further work. The book also contains discussions of structure-factor statistics, of value for resolving space-group ambiguities, and atomic displacement parameters which form an inseparable part of the structure. A discussion ofthe refinement of structural parameters, conventional, constrained and restrained, concludes the book. Derivations are, as far as possible, self contained and wherever mathematical detail might disrupt the line of reasoning the reader is referred to one of four appendices present in the book. The book is of course valuable for students of crystallography at a graduate and upper undergraduate level. No previous course on crystallography is a prerequisite for graduates in the above fields.