Crystal Structure Refinement


Book Description

Crystal Structure Refinement is a mixture of textbook and tutorial. As A Crystallographers Guide to SHELXL it covers advanced aspects of practical crystal structure refinement, which have not been much addressed by textbooks so far. After an introduction to SHELXL in the first chapter, a brief survey of crystal structure refinement is provided. Chapters three and higher address the various aspects of structure refinement, from the treatment of hydrogen atoms to the assignment of atom types, to disorder, to non-crystallographic symmetry and twinning. One chapter is dedicated to the refinement of macromolecular structures and two short chapters deal with structure validation (one for small molecule structures and one for macromolecules). In each of the chapters the book gives refinement examples, based on the program SHELXL, describing every problem in detail. It comes with a CD-ROM with all files necessary to reproduce the refinements.




Powder Diffraction


Book Description

Crystal structure analysis from powder diffraction data has attracted considerable and ever growing interest in the last decades. X-ray powder diffraction is best known for phase analysis (Hanawalt files) dating back to the 30s. In the late 60s the inherent potential of powder diffraction for crystallographic problems was realized and scientists developed methods for using powder diffraction data at first only for the refinement of crystal structures. With the development of ever growing computer power profile fitting and pattern decomposition allowed to extract individual intensities from overlapping diffraction peaks opening the way to many other applications, especially to ab initio structure determination. Powder diffraction today is used in X-ray and neutron diffraction, where it is a powerful method in neutron diffraction for the determination of magnetic structures. In the last decade the interest has dramatically improved. There is hardly any field of crystallography where the Rietveld, or full pattern method has not been tried with quantitative phase analysis the most important recent application.




Rietveld Refinement


Book Description

Almost 50 years have passed since the famous papers of Hugo Rietveld from the late sixties where he describes a method for the refinement of crystal structures from neutron powder diffraction data. Soon after, the potential of the method for laboratory X-ray powder diffraction was discovered. Although the method is now widely accepted, there are still many pitfalls in the theoretical understanding and in practical daily use. This book closes the gap with a theoretical introduction for each chapter followed by a practical approach. The flexible macro type language of the Topas Rietveld software can be considered as the defacto standard.




Crystal Structure Refinement


Book Description

Accompanying CD-ROM contains all the files necessary to reproduce the refinements covered in the text.




Crystal Structure Determination


Book Description

A concise introduction to modern crystal structure determination, emphasizing both the crystallographic background and the successive practical steps. In the theoretical sections, more importance is attached to a good understanding, than to a rigorous mathematical treatment. The most important measuring techniques, including the use of modern area detectors, and the methods of data reduction, structure solution and refinement are discussed from a practical point of view. Special emphasis is put on the ability to recognize and avoid possible errors and traps, and to judge the quality of results.




Crystal Structure Analysis


Book Description

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.




Crystal Structure Analysis


Book Description

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.




21st Century Challenges in Chemical Crystallography I


Book Description

This volume summarises recent developments and possible future directions for small molecule X-ray crystallography. It reviews specific areas of crystallography which are rapidly developing and places them in a historical context. The interdisciplinary nature of the technique is emphasised throughout. It introduces and describes the chemical crystallographic and synchrotron facilities which have been at the cutting edge of the subject in recent decades. The introduction of new computer-based algorithms has proved to be very influential and stimulated and accelerated the growth of new areas of science. The challenges which will arise from the acquisition of ever larger databases are considered and the potential impact of artificial intelligence techniques stressed. Recent advances in the refinement and analysis of X-ray crystal structures are highlighted. In addition the recent developments in time resolved single crystal X-ray crystallography are discussed. Recent years have demonstrated how this technique has provided important mechanistic information on solid-state reactions and complements information from traditional spectroscopic measurements. The volume highlights how the prospect of being able to routinely “watch” chemical processes as they occur provides an exciting possibility for the future. Recent advances in X-ray sources and detectors that have also contributed to the possibility of dynamic single-crystal X-ray diffraction methods are presented. The coupling of crystallography and quantum chemical calculations provides detailed information about electron distributions in crystals and has resulted in a more detailed understanding of chemical bonding. The volume will be of interest to chemists and crystallographers with an interest in the synthesis, characterisation and physical and catalytic properties of solid-state materials. Postgraduate students entering the field will benefit from a historical introduction to the subject and a description of those techniques which are currently used. Since X-ray crystallography is used so widely in modern chemistry it will serve to alert senior chemists to those developments which will become routine in coming decades. It will also be of interest to the broad community of computational chemists who study chemical systems.




Fundamentals of Powder Diffraction and Structural Characterization of Materials, Second Edition


Book Description

A little over ?ve years have passed since the ?rst edition of this book appeared in print. Seems like an instant but also eternity, especially considering numerous developments in the hardware and software that have made it from the laboratory test beds into the real world of powder diffraction. This prompted a revision, which had to be beyond cosmetic limits. The book was, and remains focused on standard laboratory powder diffractometry. It is still meant to be used as a text for teaching students about the capabilities and limitations of the powder diffraction method. We also hope that it goes beyond a simple text, and therefore, is useful as a reference to practitioners of the technique. The original book had seven long chapters that may have made its use as a text - convenient. So the second edition is broken down into 25 shorter chapters. The ?rst ?fteen are concerned with the fundamentals of powder diffraction, which makes it much more logical, considering a typical 16-week long semester. The last ten ch- ters are concerned with practical examples of structure solution and re?nement, which were preserved from the ?rst edition and expanded by another example – R solving the crystal structure of Tylenol .




The Weak Hydrogen Bond


Book Description

The weak or non-conventional hydrogen bond has been subject of intense scrutiny over recent years in several fields, in particular in structural chemistry, structural biology, and also in the pharmaceutical sciences. There is today a large body of experimental and theoretical evidenceconfirming that hydrogen bonds like C-H...O, N-H...pi, C-H...pi and even bonds like O-H...metal play distinctive roles in molecular recognition, guiding molecular association, and in determining molecular and supramolecular architectures. The relevant compound classes include organometalliccomplexes, organic and bio-organic systems, and also DNA and proteins. The book provides a comprehensive assessment of this interaction type, and is of interest to all those interested in structural and supramolecular science, including fields as crystal engineering and drug design.