Perspectives In Quantum Chemistry

This book explores the philosophy and the foundations of quantum chemistry. It features chapters written by experts in the field. The contributions analyze quantum chemistry as a discipline, in particular, its relation with both chemistry and physics from the viewpoint of realism and reduction. Coverage includes such topics as quantum chemistry as an “in-between” discipline, molecular structure and quantum mechanics, quantum chemical models, and atoms and molecules in quantum chemistry. The interest of this book is twofold. First, the contributions aim to update and refresh the discussions regarding the foundations of quantum chemistry. Second, they seek to develop new philosophical perspectives that this discipline can suggest to philosophers of science. From its origins, quantum chemistry filled a problematic position in the disciplinary space. On the one hand, it is a branch of theoretical chemistry. On the other hand, it appeals essentially to theoretical tools coming from physics. This peculiar position triggered conceptual questions about its own identity. Inside this book, readers will find updated discussions on the foundations and the philosophy of this complex discipline.

The rivers run into the sea, yet the sea is not full Ecclesiastes What is quantum chemistry? The straightforward answer is that it is what quan tum chemists do. But it must be admitted, that in contrast to physicists and chemists, "quantum chemists" seem to be a rather ill-defined category of scientists. Quantum chemists are more or less physicists (basically theoreticians), more or less chemists, and by large, computationists. But first and foremost, we, quantum chemists; are conscious beings. We may safely guess that quantum chemistry was one of the first areas in the natural sciences to lie on the boundaries of many disciplines. We may certainly claim that quantum chemists were the first to use computers for really large scale calculations. The scope of the problems which quantum chemistry wishes to answer and which, by its unique nature, only quantum chemistry can answer is growing daily. Retrospectively we may guess that many of those problems meet a daily need, or are say, technical in some sense. The rest are fundamental or conceptual. The daily life of most quantum chemists is usually filled with grasping the more or less technical problems. But it is at least as important to devote some time to the other kind of problems whose solution will open up new perspectives for both quantum chemistry itself and for the natural sciences in general.

The purpose of this book is to provide a deeper insight into the modern theories of molecular matter. It incorporates the most important developments which have taken place during the last decades and reflects the modern trend to abstraction. At the present state of the art we have acquired a fairly good knowledge of "how to. compute" small molecules us ing the methods of quantum chemistry. Yet, in spite of many statements to the contrary and many superficial discussions, the theoretical basis of chemistry and biology is not safely in our hands. It is all but impossible to summarize the modern developments of the theory of matter in nontechnical language. But I hope that I can give some feeling for the problems, the intellectual excitements and the wor ries of some theoreticians. I know very well that such an enterprise is a dangerous adventure and that one says that a clever scientist should take care of his reputation by barricading himself behind the safe wall of his speciality. This volume is not meant to be a textbook; in many respects it has complementary goals. For good and bad reasons, most textbooks ignore the historical and philosophical aspects and go ahead on the basis of crude simplifications; many even lie like the devil and do not shrink from naive indoctrination. Some sections of this book can be read as commentaries on our standard texts, they are intended to stir the waters with controversy.

The Sixth International Congress on Quantum Chemistry convened at the Campus of the Hebrew University. Jerusalem. Israel. on August 22-25. 1988. The International Congresses on Quantum Chemistry are held under the auspices of the International Academy of Quantum Molecular Science. Previous International Congresses on Quantum Chemistry were held in France. Japan, the United States, Sweden and Canada. These prestigious meetings provided a central contribution to the important modern area of theoretical chemistry. The major goals of the Sixth International Congress on Quantum Chemistry were: A) To provide an overview of recent novel developments. advances and directions of research in the broad area of quantum molecular sciences. B) To establish strong interaction between the theoretical discipline of quantum molecular sciences and experiment. The general topics of the Sixth International Congress were: a) Molecular Quantum Mechanics b) Many-Body Theory of Molecular Structure c) Intermolecular Forces d) Complexes and Clusters e) Molecular Spectroscopy f) Intramolecular Dynamics g) Chemical Reactions h) Molecular Dynamics Simulations i) Condensed-Phase Chemistry j) Surface Phenomena and Catalysis k) Quantum Biochemistry 1) Biophysics The format of the Sixth International Congress consisted of plenary lectures. symposia and poster sessions. In the opening session of the Congress. commemorative addresses were delivered in honoured memory of the late Louis de Broglie and the late Robert S. Mulliken. Nobel Prize Laureates and Members of the International Academy of Quantum Molecular Science. A com memorative symposium was devoted to the honoured memory of the late Massimo Simonetta.

The understanding in science implies insights from several different points of view. Alternative modern outlooks on electronic structure of atoms and molecules, all rooted in quantum mechanics, are presented in a single text. Together these complementary perspectives provide a deeper understanding of the localization of electrons and bonds, the origins of chemical interaction and reactivity behavior, the interaction between the geometric and electronic structure of molecules, etc. In the opening two parts the basic principles and techniques of the contemporary computational and conceptual quantum chemistry are presented, within both the wave-function and electron-density theories. This background material is followed by a discussion of chemical concepts, including stages of the bond-formation processes, chemical valence and bond-multiplicity indices, the hardness/softness descriptors of molecules and reactants, and general chemical reactivity/stability principles. The insights from Information Theory, the basic elements of which are briefly introduced, including the entropic origins and Orbital Communication Theory of the chemical bond, are the subject of Part IV. The importance of the non-additive (interference) information tools in exploring patterns of chemical bonds and their covalent and ionic components will be emphasized.

Emergent quantum mechanics explores the possibility of an ontology for quantum mechanics. The resurgence of interest in "deeper-level" theories for quantum phenomena challenges the standard, textbook interpretation. The book presents expert views that critically evaluate the significance—for 21st century physics—of ontological quantum mechanics, an approach that David Bohm helped pioneer. The possibility of a deterministic quantum theory was first introduced with the original de Broglie-Bohm theory, which has also been developed as Bohmian mechanics. The wide range of perspectives that were contributed to this book on the occasion of David Bohm’s centennial celebration provide ample evidence for the physical consistency of ontological quantum mechanics. The book addresses deeper-level questions such as the following: Is reality intrinsically random or fundamentally interconnected? Is the universe local or nonlocal? Might a radically new conception of reality include a form of quantum causality or quantum ontology? What is the role of the experimenter agent? As the book demonstrates, the advancement of ‘quantum ontology’—as a scientific concept—marks a clear break with classical reality. The search for quantum reality entails unconventional causal structures and non-classical ontology, which can be fully consistent with the known record of quantum observations in the laboratory.

Introduction to Quantum Mechanics covers quantum mechanics from a time-dependent perspective in a unified way from beginning to end. Intended for upper-level undergraduate and graduate courses this text will change the way people think about and teach quantum mechanics in chemistry and physics departments.

The rivers run into the sea, yet the sea is not full Ecclesiastes What is quantum chemistry? The straightforward answer is that it is what quan tum chemists do. But it must be admitted, that in contrast to physicists and chemists, "quantum chemists" seem to be a rather ill-defined category of scientists. Quantum chemists are more or less physicists (basically theoreticians), more or less chemists, and by large, computationists. But first and foremost, we, quantum chemists, are conscious beings. We may safely guess that quantum chemistry was one of the first areas in the natural sciences to lie on the boundaries of many disciplines. We may certainly claim that quantum chemists were the first to use computers for really large scale calculations. The scope of the problems which quantum chemistry wishes to answer and which, by its unique nature, only quantum chemistry can only answer is growing daily. Retrospectively we may guess that many of those problems meet a daily need, or are say, technical in some sense. The rest are fundamental or conceptual. The daily life of most quantum chemists is usually filled with grasping the more or less technical problems. But it is at least as important to devote some time to the other kind of problems whose solution will open up new perspectives for both quantum chemistry itself and for the natural sciences in general.