Mark Ladd Rex Palmer Structure Determination by X-ray Crystallography Analysis by X-rays and Neutrons Fifth Edition Structure Determination by X-ray Crystallography OfficialcontributionoftheNationalInstituteofStandardsandTechnology;notsubjecttocopyrightintheUnitedStates [ReproducedbycourtesyofN.I.S.T.] Mark Ladd (cid:129) Rex Palmer Structure Determination by X-ray Crystallography Analysis by X-rays and Neutrons Fifth Edition Celebrating the Centenary of X-ray Crystallography MarkLadd RexPalmer FormerlyHeadofChemicalPhysics ReaderEmeritusinStructuralCrystallography UniversityofSurrey BirkbeckCollege,UniversityofLondon, Guildford,England London,England VisitingProfessorinX-rayCrystallography UniversityofGreenwich,England SeniorVisitingResearchFellow ChristChurchUniversity, Canterbury,England Additionalmaterialtothisbookcanbedownloadedfromhttp://extra.springer.com. 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Lord Kelvin To Valentia and Hilda Foreword I am privileged to write the Foreword to this fifth edition of Ladd and Palmer’s Structure Determination by X-ray Crystallography, a textbook thatisnowworldrenownedandthathashelpededucatetwogenerationsof crystallographers in the theory and practice of modern crystallography, myself included. Indeed, a well-worn first edition of this venerable text remains on my shelves today, now somewhat battered and bruised from passage through the hands of successive students who have learned the fundamentalsofcrystallographyfromitspages. Thisnewfiftheditionisespeciallytimely,markingasitdoesacentury of discovery in which X-ray diffraction, and diffraction of other radiations, hasopenedawindowtotheatomicworld.Fromfundamentalknowledgeof atomic interactions and chemical bonds in the simplest materials to the atomic resolution analysis of the molecular machines of the cell, crystallo- graphicscienceunderpinsmuchofourunderstandingoftheworldwelivein today. In recent years, advances in diffraction theory, automated technolo- gies, and computational tools have helped move crystallography from a specialist discipline to a standard laboratory tool across many fields of science.Insomefields,theseadvanceshavebeensospectacularlysuccessful that the solution of the crystal structures of all but the most challenging systems is now considered largely routine. At the same time, the develop- ment of a new generation of high powered synchrotron, neutron and, most recently,freeelectronlaserfacilitiesarepushingcrystallographicscienceto newfrontiers,aimingtoprovidediffractionfromsinglemolecules,tolocate lightatomssuchashydrogenincrystalstructures,andtomovebeyondstatic crystal structures towards time-resolved analyses of structural dynamics at pico-secondtimescales. For the interdisciplinary students of today seeking a thorough and detailed understanding of the principles and methods of modern crystallog- raphy, Ladd and Palmer remains as essential and relevant today as when it firstappearedsome35yearsago.Buildingfromthefundamentalconceptsof crystallography,throughcrystalsymmetrytothemathematicalformalismof diffractionandontotheprincipleandpracticeofstructuredetermination,the textprovidesanexcellentintroductiontothetechniquesandapplicationsof crystallography, illustrated throughout by applications to real world pro- blems. The fifth edition is expanded and enhanced with updated examples anddescriptionofrecenttechnicaldevelopmentsandachievementsinX-ray crystallography and benefits from a completely new chapter that describes ix