This book is by far the most comprehensive treatment of point and space groups, and their meaning and applications. Its completeness makes it especially useful as a text, since it gives the instructor the flexibility to best fit the class and goals. The instructor, not the author, decides what is in the course. And it is the prime book for reference, as material is much more likely to be found in it than in any other book; it also provides detailed guides to other sources.Much of what is taught is folklore, things everyone knows are true, but (almost?) no one knows why, or has seen proofs, justifications, rationales or explanations. (Why are there 14 Bravais lattices, and why these? Are the reasons geometrical, conventional or both? What determines the Wigner-Seitz cells? How do they affect the number of Bravais lattices? Why are symmetry groups relevant to molecules whose vibrations make them unsymmetrical? And so on). Here these analyses are given, interrelated, and in-depth. The understanding so obtained gives a strong foundation for application and extension. Assumptions and restrictions are not merely made explicit, but also emphasized.In order to provide so much information, details and examples, and ways of helping readers learn and understand, the book contains many topics found nowhere else, or only in obscure articles from the distant past. The treatment is (often completely) different from those elsewhere. At least in the explanations, and usually in many other ways, the book is completely new and fresh. It is designed to inform, educate and make the reader think. It strongly emphasizes understanding.The book can be used at many levels, by many different classes of readers ? from those who merely want brief explanations (perhaps just of terminology), who just want to skim, to those who wish the most thorough understanding.

This volume is the second of a set of two which contain 28 selected from the l. j. O invited lectures given at the internatim;al seminar of the same title held at the Centre de Mecanique Ondulatoire Appliquee du Centre National de la Recherche Scientifique in Paris (France) from October 1983 to May 1985. They are intended to provide a survey of topics of current interest relative to the structure and the dynamics of molecular systems. The papers have been selected on the basis of their relevance to the following four topics: i) molecular conformations and transformations; H) molecular relaxation and motion; iii) charge, spin and momentum distributions and intermolecular interactions; iv) collective phenomena in condensed matter. The first volume deals mostly with the first two topics, the second volume mostly with the last two. The two volumes consist of an approximately equal number of self-con tained, reference contributions covering recent achievements in active branches of molecular physics and physical chemistry. The first two papers of the present volume deal with theoretical aspects of intermolecular interactions: the first paper with the physical origin of the so-called non-exchange molecular terms, a complete deriva tion of which is given using Rayleigh-Schrodinger second-order perturba tion theory; the second paper with the symmetry analysis of the effects of interactions between rigid molecules and crystal environments, using the isodynamic-group theoretical approach devised by Altmann for non rigid systems.

This book delivers a comprehensive account of the main features and possibilities of LCAO methods for the first principles calculations of electronic structure of periodic systems. The first part describes the basic theory underlying the LCAO methods applied to periodic systems and the use of wave-function-based, density-based (DFT) and hybrid hamiltonians. The second part deals with the applications of LCAO methods for calculations of bulk crystal properties.

The Advanced Study Institute on "Quantum Dynamics of Molecules: The New Experimental Challenge to Theorists," which was sponsored by the Scientific Affairs Division of NATO, was held at Trinity Hall, Ca~bridge, England from September 15th till September 29th, 1979. In all, a total of 79 lecturers and students attended the meeting: they had diverse backgrounds in chemistry, physics and mathematics. In my proposal to NATO requesting financial support for an Advanced Study Institute, I suggested that molecular physics was facing a qualitatively new experimental situation in which the exploration of previously inaccessible dynamical phenomena would become of increasing importance. At the same time I was aware that in recent years powerful theoretical techniques, that might prove crucial tools for the interpretation of the new experiments, have been developed in mathematics and theoretical physics. The aim of the ASI was to review at an advanced level these recent developments, juxtaposing new theory with new experimental pos sibilities in the hope that the participants in the-Institute would through their subsequent work increase the awareness of the whole molecular theory community of the changing nature of chemical physics. The recent developments in laser spectroscopy, particle scatter ing experiments and molecular beam technology imply that an entirely new class of phenomena involving molecules in gasses and liquids can now be investigated.

This text presents a consistent description of the geometric and quaternionic treatment of rotation operators. Covers the fundamentals of symmetries, matrices, and groups and presents a primer on rotations and rotation matrices. Also explores rotations and angular momentum, tensor bases, the bilinear transformation, projective representations, more. Includes problems with solutions.

From the pioneering author in the field, this book is ideal for condensed matter physicists and physical chemists.