The second volume of the proceedings of the international seminar devoted to locali· zation and delocalization in quantum chemistry is divided into four parts. The first one is mainly concerned with the localizability of electrons in ionized and exited states. The second part shows how is it possible to take advantage of the localizability of electrons to compute molecular wave-functions. The third part of the book is an homogeneous analysis of the electronic collective excitation and of the motion of excitons in organic solids. The last section is devoted to the study of the role of electron localizability in the chemical reactivity of molecules. Concluding remarks are concerned with a careful analysis of the localizability concept itself in relation with a possible interpretation of the wave-mechanics. PART I ELECTRON LOCALIZATION IN IONIZED AND EXCITED STATES APPLICATIONS OF PAIR DENSITY ANALYSIS R. CONSTANCIEL and L. ESNAULT Centre de Mecanique Ondulatoire Appliquee, Paris, France Abstract. The method of pair density analysis is applied to various kinds of calculations. We examine the influence of the quality of the wavefunction and of the nuclear configuration; the problem of hybridization is discussed, as weIl as the relations between separability and excitation.

This is the perfect complement to "Chemical Bonding - Across the Periodic Table" by the same editors, who are two of the top scientists working on this topic, each with extensive experience and important connections within the community. The resulting book is a unique overview of the different approaches used for describing a chemical bond, including molecular-orbital based, valence-bond based, ELF, AIM and density-functional based methods. It takes into account the many developments that have taken place in the field over the past few decades due to the rapid advances in quantum chemical models and faster computers.

In recent years, problems such as environmental and economic crises and pandemics caused by new viruses have been occurring on a global scale. Globalization brings about benefits, but it can increase the potential risks of “systemic problems”, leading to system-wide disruptions. The coronavirus pandemic, declared on March 11, 2020, by the World Health Organization, has revealed social disparities in the form of a higher risk of death for people of low-socioeconomic status and has caused massive destruction of the economy and of globalization itself. Extensive efforts to cope with these challenges have often led to the emergence of additional problems due to the chain of hidden causation. What can be done to protect against such emerging challenges? Despite the resulting complexity, once these individual problems are considered as different aspects of a single whole, seemingly contradictory issues can become totally understandable, as they can be integrated into a single coherent framework. This is the integrationist approach in contrast to the reductionist approach. Situations of this kind are truly relevant to understanding the question, “What are creative complex systems?” This book features contributions by members and colleagues of the Kyoto University International Research Unit of Integrated Complex System Science. It broadens our outlook from the traditional view of stability, in which global situations are eventually stabilized after the impact of destruction, to “creative” complex systems.

Quantum Crystallography is a novel scientific discipline combining quantum chemistry methods and crystal structure determination. The current book describes quantum-mechanical approaches to obtain crystallographic data of enhanced value and explains how they correlate with real diffraction and scattering experiments. In particular, the book covers DFT, Clinton equations, KEM and QTAIM methods and their applications in crystallographic studies.

Con esta obra se pretenden unificar los fundamentos, métodos y técnicas de la química teórica y computacional. Además, cabe comentar que la presente edición no sólo va dirigida a estudiantes de doctorado (a fin de proporcionarles un nivel adecuado para sus estudios), sino que la materia se trata de manera suficientemente detallada para que lectores no tan expertos puedan acceder a ella sin ninguna dificultad

Principles and Applications of Quantum Chemistry offers clear and simple coverage based on the author's extensive teaching at advanced universities around the globe. Where needed, derivations are detailed in an easy-to-follow manner so that you will understand the physical and mathematical aspects of quantum chemistry and molecular electronic structure. Building on this foundation, this book then explores applications, using illustrative examples to demonstrate the use of quantum chemical tools in research problems. Each chapter also uses innovative problems and bibliographic references to guide you, and throughout the book chapters cover important advances in the field including: Density functional theory (DFT) and time-dependent DFT (TD-DFT), characterization of chemical reactions, prediction of molecular geometry, molecular electrostatic potential, and quantum theory of atoms in molecules. - Simplified mathematical content and derivations for reader understanding - Useful overview of advances in the field such as Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) - Accessible level for students and researchers interested in the use of quantum chemistry tools

Advances in Quantum Chemical Topology Beyond QTAIM provides a complete overview of the field, starting with traditional methods and then covering key steps to the latest state-of-the-art extensions of QTAIM. The book supports researchers by compiling and reviewing key methods, comparing different algorithms, and providing computational results to show the efficacy of the approaches. Beginning with an introduction to quantum chemistry, QTAIM and key extensions, the book goes on to discuss interacting quantum atoms and related energy properties, explores partitioning methods, and compares algorithms for QTAIM. Partitioning schemes are them compared in more detail before applications are explored and future developments discussed. Drawing together the knowledge of key authorities in the area, this book provides a comprehensive, pedogeological guide to this insightful theory for all those interested in modelling, exploring and understanding molecular properties. - Provides a contemporary review of the extensions and application of QTAIM methods - Compiles all extensions of QTAIM in one place for easy reference - Includes a chapter with an Introduction to Quantum Chemistry - Presents complex information at a level accessible to those engaged in theoretical/computational chemistry

This book distills the knowledge gained from research into atoms in molecules over the last 10 years into a unique, handy reference. Throughout, the authors address a wide audience, such that this volume may equally be used as a textbook without compromising its research-oriented character. Clearly structured, the text begins with advances in theory before moving on to theoretical studies of chemical bonding and reactivity. There follow separate sections on solid state and surfaces as well as experimental electron densities, before finishing with applications in biological sciences and drug-design. The result is a must-have for physicochemists, chemists, physicists, spectroscopists and materials scientists.