Dynamical Scattering Of X Rays In Crystals

(Historical Survey) The discovery of X-ray diffraction in crystals by LAUE, FRIDRICH and KNIPPING in 1912 [1.1] served as the starting pOint for the development of scientific research along a number of important lines. We shall discuss just a few of them. The above discovery convincingly demonstrated the wave properties of X-rays. This, together with the previously established electromagnetic nature of radiation, confirmed the hypothesis that X-rays form the short-wave part of the electromagnetic spectrum. Further, this discovery was the first and decisive experimental proof of the periodic structure of crystals. In fact, theoretical crystallography had already arrived at this conclusion, mainly as an outcome of the theory of the space groups of symmetry elaborated by FEDOROV [1.2] and SCHOENFLIES [1.3]. From the optics of visible light we know that the radiation of a wave length of the same order as, and preferably less than, the period of a grat ing suffers diffraction on periodic objects of the type of optical grating. Thus, the discovery proved that the wavelength of an X-ray must be of the order of interatomic distances. It became clear why the visible light of wavelengths exceeding the crystal lattice periods by about 500 to 1000 times failed to reveal the periodic structure of crystals in diffraction experi ments.

This volume collects the proceedings of the 23rd International Course of Crystallography, entitled "X-ray and Neutron Dynamical Diffraction, Theory and Applications," which took place in the fascinating setting of Erice in Sicily, Italy. It was run as a NATO Advanced Studies Institute with A. Authier (France) and S. Lagomarsino (Italy) as codirectors, and L. Riva di Sanseverino and P. Spadon (Italy) as local organizers, R. Colella (USA) and B. K. Tanner (UK) being the two other members of the organizing committee. It was attended by about one hundred participants from twenty four different countries. Two basic theories may be used to describe the diffraction of radiation by crystalline matter. The first one, the so-called geometrical, or kinematical theory, is approximate and is applicable to small, highly imperfect crystals. It is used for the determination of crystal structures and describes the diffraction of powders and polycrystalline materials. The other one, the so-called dynamical theory, is applicable to perfect or nearly perfect crystals. For that reason, dynamical diffraction of X-rays and neutrons constitutes the theoretical basis of a great variety of applications such as: • the techniques used for the characterization of nearly perfect high technology materials, semiconductors, piezoelectric, electrooptic, ferroelectric, magnetic crystals, • the X-ray optical devices used in all modem applications of Synchrotron Radiation (EXAFS, High Resolution X-ray Diffractometry, magnetic and nuclear resonant scattering, topography, etc. ), and • X-ray and neutron interferometry.

Publisher Description

Exploration of fundamentals of x-ray diffraction theory using Fourier transforms applies general results to various atomic structures, amorphous bodies, crystals, and imperfect crystals. 154 illustrations. 1963 edition.

Mikhail Alexandrovich Krivoglaz died unexpectedly when he was preparing the English edition of his two-volume monograph on diffraction and diffuse scatter ing of X-rays and neutrons in imperfect crystals. His death was a heavy blow to all who knew him, who had worked with him and to the world science community as a whole. The application of the diffraction techniques for the study of imperfections of crystal structures was the major field of Krivoglaz' work throughout his career in science. He started working in the field in the mid-fifties and since then made fundamental contributions to the theory of real crystals. His results have largely determined the current level of knowledge in this field for more than thirty years. Until the very last days of his life, Krivoglaz continued active studies in the physics of diffraction effects in real crystals. His interest in the theory aided in the explanation of the rapidly advancing experimental studies. The milestones marking important stages of his work were the first mono graph on the theory of X-ray and neutron scattering in real crystals which was published in Russian in 1967 (a revised English edition in 1969), and the two volume monograph published in Russian in 1983-84 (this edition is the revised translation of the latter).

The three-dimensional arrangement of atoms and molecules in crystals and the comparable magnitude of x-ray wavelengths and interatomic distances make it possible for crystals to have more than one set of atomic planes that satisfy Bragg's law and simultaneously diffract an incident x-ray beam - this is the so-called multiple diffraction. This type of diffraction should, in prin ciple, reflect three-dimensional information about the structure of the dif fracting material. Recent progress in understanding this diffraction phenome non and in utilizing this diffraction technique in solid-state and materials sciences reveals the diversity as well as the importance of multiple diffraction of x-rays in application. Unfortunately, there has been no single book written that gives a sys tematic review of this type of diffraction, encompasses its diverse applica tions, and foresees future trends gf development. It is for this purpose that this book is designed. It is hoped that its appearance may possibly turn more attention of condensed-matter physicists, chemists and material scientists toward this particular phenomenon, and that new methods of non-destructive analysis of matter using this diffraction technique may be developed in the future.