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.

1. A Priori Geometry Predictions.- 1. Introduction.- 2. Equilibrium Geometries by Hartree-Fock Theory.- 3. Equilibrium Geometries with Correlation.- 4. Predictive Structures for Radicals and Cations.- 5. Conclusions.- References.- 2. Barriers to Rotation and Inversion.- 1. Introduction.- 2. Assessment of Computational Methods.- 3. Methods for Analyzing Rotational Barrier Mechanisms.- 4. Semiempirical Models.- References.- 3. Hydrogen Bonding and Donor-Acceptor Interactions.- 1 Introduction.- 2. Theoretical Methods.- 3. Observable Properties of Hydrogen-Bonded and Other Donor-Acceptor Complexes.- 4. Generalizations about the Hydrogen Bond.- 5. Summary.- References.- 4. Direct Use of the Gradient for Investigating Molecular Energy Surfaces.- 1. Gradient Method Versus Pointwise Calculations.- 2. Calculation of the Energy Gradient from SCF Wave Functions.- 3. Applications.- 4. Analytical Calculation of Higher Energy Derivatives.- References.- 5. Transition Metal Compounds.- 1. Introduction.- 2. The Technique of Ab Initio LCAO-MO-SCF Calculations.- 3. Bonding in Transition Metal Compounds.- 3.1. Bondingin "Classical" Complexes: CuCl42-.- 3.2. Bonding in Complexes of ?-Acceptor Ligands: Fe(CO)5.- 3.3. Bonding in Some Organometallics.- 4. The Concept of Orbital Energy and the Interpretation of Electronic and Photoelectron Spectra.- 5. Electronic Structure and Stereochemistry of Dioxygen Adducts of Cobalt-Schiff-Base Complexes.- References.- 6. Strained Organic Molecules.- 1. Introduction.- 2. The Nature of Strained Organic Molecules.- 3. Theoretical Methods for Strained Organic Systems.- 4. Discussion of Ab Initio Results.- 5. Summary.- References.- 7. Carbonium Ions: Structural and Energetic Investigations.- 1. Introduction.- 2. CH+.- 3. CH3+.- 4. CH5+.- 5. C2H+.- 6.C2H3+.- 7. C2H5+.- 8. C2H7+.- 9. C3H+.- 10. C3H3+.- 11. C3H5+.- 12. C3H7+.- 13. C4H5+.- 14. C4H7+.- 15. C4H9+.- 16. C5H5+.- 17. C6H7+.- 18. C7H7+.- 19. C8H9+.- 20. Conclusion.- References.- 8. Molecular Anions.- 1. Introduction.- 2. Background.- 3. Structural Studies.- 4. Heats of Reaction.- 5. Mechanistic Studies.- 6. Conclusions.- References.- 9. Electron Spectroscopy.- 1. Introduction.- 2. Studies of Valence Electrons.- 3. Studies of Core Electrons.- 4. Summary and Prospectus for the Future.- References.- 10. Molecular Fine Structure.- 1. Introduction.- 2. Theory.- 3. Computational Aspects.- 4. Numerical Studies of Fine Structure.- 5. Phenomena Related to Fine Structure.- 6. Conclusions.- Appendix. Vibration-Rotation Corrections to the ZFS Parameters.- References.- Author Index.