Oxford University Press
2014 | 414pp | £65
Reviewed by Richard Cooper
In x-ray, neutron or electron diffraction experiments, only the magnitude of the constructively interfering waves from a sample is measured; the relative phases of these waves are lost. But this is valuable information that permits computation of the scattering density of the crystal structure at atomic resolution. Thus, the notorious phase problem: how to determine the phases of the waves. The various solutions to this problem are covered in depth in this book.
In the century since the discovery of diffraction of x-rays by crystals, methods for solving the ‘phase problem’ have allowed crystal structures of increasing complexity to be determined with decreasing human intervention.
Phasing in crystallography has its origins in Carmelo Giacovazzo’s monograph Direct phasing in crystallography, but with a broader coverage of the range of modern phasing methods. The subject matter is logically arranged, in order of increasing complexity, so that later chapters on phasing data from neutron diffraction, powder diffraction and macromolecular structures build upon the earlier topics such as Wilson statistics, phase improvement and Patterson methods. Chapters describing recent developments in ab initio phasing, such as charge flipping and the author’s own algorithm are also a welcome inclusion.
The author manages to balance precise and consistent mathematical formulae with informative analogies and real crystallographic applications, which make this a rare and useful reference text for those using crystallographic tools in their everyday research. Despite the relegation of proofs and derivations to chapter-based appendices, the content is still mathematically demanding and it is unlikely that many readers will take a linear approach to reading this book and instead will delve into chapters on specific techniques as required.
Commentators often lament the black-box nature of crystallographic structure solution software, which is in part because of the automation of the techniques and methods described in this book. Phasing in crystallography provides a window into that box for professional crystallographers, researchers working with crystallographic results and the next generation of researchers developing and testing new ideas in the subject.