This book contains the transcripts of the lectures presented at the NATO Advanced Study Institute on "Electrons in Finite and Infinite Structures," held at the State University of Ghent, Belgium, August 30-September 11, 1976. Over the last few years substantial progress has been made in the description and the understanding of the behavior of electrons in extended bodies. This includes the study of the energy spectrum of electrons in large molecules, perfect as well as imperfect crys tals, and disordered alloys. Not only local potential techniques but also the many-body aspects are discussed in detail. As atomic, molecular, and solid state physics involve common techniques and insights, we believe that physicists and chemists active in these fields have benefited from these lectures and the interchange of ideas during the course. The aim of the Institute was to familiarize young scientists in the field with the current state of the art and to indicate in which areas advances may be expected in the near future. The A.S.I. consisted of two parts: detailed instructional and review lectures over the whole period and some evening sessions where the partici pants were offered the opportunity to present their own work and discuss their ideas with senior scientists. Since the Institute took place a few weeks after Prof. Dr. John C. Slater was suddenly taken from our scientific community, it was a great honor for us to dedicate this course, on behalf of the organizing committee, to the late John C. Slater.

These two volumes deal with the quantum theory of the electronic structure of molecules. Implicit in the term ab initio is the notion that approximate solutions of Schrödinger's equation are sought "from the beginning," i. e. , without recourse to experimental data. From a more pragmatic viewpoint, the distin guishing feature of ab initio theory is usually the fact that no approximations are involved in the evaluation of the required molecular integrals. Consistent with current activity in the field, the first of these two volumes contains chapters dealing with methods per se, while the second concerns the application of these methods to problems of chemical interest. In asense, the motivation for these volumes has been the spectacular recent success of ab initio theory in resolving important chemical questions. However, these applications have only become possible through the less visible but equally important efforts of those develop ing new theoretical and computational methods and models. Henry F Schaefer Vll Contents Contents of Volume 4 XIX Chapter 1. Gaussian Basis Sets for Molecular Calculations Thom. H. Dunning, Ir. and P. Ieffrey Hay 1. Introduction . . . . . . . . . . . . . . . . 1 1. 1. Slater Functions and the Hydrogen Moleeule 1 1. 2. Gaussian Functions and the Hydrogen Atom 3 2. Hartree-Fock Calculations on the First Row Atoms 5 2. 1. Valence States of the First Row Atoms 6 7 2. 2. Rydberg States of the First Row Atoms 9 2. 3.

These two volumes deal with the quantum theory of the electronic structure of ab initio is the notion that approximate solutions molecules. Implicit in the term of Schrodinger's equation are sought "from the beginning," i. e. , without recourse to experimental data. From a more pragmatic viewpoint, the distin guishing feature of ab initio theory is usually the fact that no approximations are involved in the evaluation of the required molecular integrals. Consistent with current activity in the field, the first of these two volumes contains chapters dealing with methods per se, while the second concerns the application of these methods to problems of chemical interest. In a sense, the motivation for these volumes has been the spectacular recent success of ab initio theory in resolving important chemical questions. However, these applications have only become possible through the less visible but equally important efforts of those developing new theoretical and computational methods and models. Henry F. Schaefer vii Contents Contents of Volume 3 xv Chapter 1. A Priori Geometry Predictions 1. A. Pople 1. Introduction . . . . . . . . . . . . . . . . . . . 1 2. Equilibrium Geometries by Hartree-Fock Theory 2 2. 1. Restricted and Unrestricted Hartree-Fock Theories 2 2. 2. Basis Sets for Hartree-Fock Studies . . . . . 4 2. 3. Hartree-Fock Structures for Small Molecules . 6 2. 4. Hartree-Fock Structures for Larger Molecules 12 3. Equilibrium Geometries with Correlation . . 18 4. Predictive Structures for Radicals and Cations 20 5. Conclusions 23 References 24 Chapter 2. Barriers to Rotation and Inversion Philip W. Payne and Leland C.

Electronic Structure of Molecules: Diatomic Molecules, Small Molecules, Saturated Hydrocarbons, Conjugated Molecules, Molecules of Biochemical Interest focuses on the study of the electronic structure of molecules and associated molecular properties. The publication first offers information on hydrogen ion-molecule and various kinds of molecular orbitals and helium atom and hydrogen molecule. Discussions focus on the method of linear combinations of atomic orbitals, method of the united atoms, and remarks on helium atom and hydrogen molecule. The text then elaborates on diatomic molecules and general problems in the structure of molecules. The book touches on molecules containing only cores and simple bonds and small molecules formed by simple bonds and unshared electrons. Topics include alicyclic paraffins and the idea of a simple bond, methane, molecules of ammonia and water in their equilibrium configurations, and relationship between electronic structure and the position of nuclei. The publication is a valuable source material for readers interested in the electronic structure of molecules.

This book explains the observed trends in the bonding and structure of molecules and solids within the models of the electronic structure. Emphasis is placed throughout on recent theoretical developments that link structural stability to the local topology or connectivity of the lattice through the moments of the electronic density of states. The chemically-intuitive Tight Binding approximation provides a unified treatment of the covalent bond in small molecules and extended solids, while the physically-intuitive Nearly-Free Electron approximation provides a natural description of the metallic bonds in sp-valent metals. Unlike the conventional reciprocal-space formulation of band theory, this modern real-space approach allows an immediate understanding of the origin of structural trends within the periodic table for the elements and the AB structure map for binary compounds. Although this unique book is aimed primarily at postgraduates in physics, chemistry, and materials science, a chapter on basic quantum mechanical concepts is included for those readers with little or no basic knowledge of the subject.