During the past few years, there has been dramatic progress in theoretical and computational studies of large molecules and local ized states in solids. Various semi-empirical and first-principles methods well known in quantum chemistry have been applied with considerable success to ever larger and more complex molecules, including some of biological importance, as well as to selected solid state problems involving localized electronic states. In creasingly, solid state physicists are adopting a molecular point of view in attempting to understand the nature of electronic states associated with (a) isolated structural and chemical defects in solids; (b) surfaces and interfaces; and (c) bulk disordered solids, most notably amorphous semiconductors. Moreover, many concepts and methods already widely used in solid state physics are being adapted to molecular problems. These adaptations include pseudopotentials, statistical exchange approxi mations, muffin-tin model potentials, and multiple scattering and cellular methods. In addition, many new approaches are being de vised to deal with progressively more complex molecular and local ized electronic state problems.

Inhalt
Welcoming Remarks.- 1. Scientific Challenges I.- Introductory Remarks.- Quantum Chemistry. Theory of Geometries and Energies of Small Molecules.- Organic Transition States.- Solid State Concepts in Radiation Chemistry and Biology.- Molecular Modeling by Computer.- 2. Scientific Challenges II.- Introductory Remarks.- Structural Characteristics and Electronic States of Hemoglobin.- Molecular Theory of Nucleation.- 3. Computational Methods I.- Approximations for Large-Molecule Calculations.- AB Initio Computation of Molecular Structures Through Configuration Interaction.- Approximate Methods in Quantum Chemistry.- LCAO-MO Cluster Model for Localized States in Covalent Solids.- Description of Molecules in Terms of Localized Orbitals.- 4. Computational Methods II.- Introductory Remarks.- The SCF-X? Scattered-Wave Method.- The Orbital Correction Method.- Panel Discussion on Computational Methods.- AB Initio SCF Calculations of the Carbazole and 2,4,7-Trinitro-9-Fluorenone (TNF) Molecules.- 5. Localized States and Disordered Solids I.- Surface States and Leed.- Wannier Functions.- Developments in Localized Pseudopotential Methods.- Localized Defects in Semiconductors.- Transmission of Electrons Through a Disordered Array of Potentials.- 6. Localized States and Disordered Solids II.- Introductory Remarks.- Electronic Structure of Amorphous Semiconductors.- Some Polytypes of Germanium and a Tight Binding Model for the Electronic Structure of Amorphous Solids.- Coexistence of Localized and Extended States?.- Cluster Scattering in Amorphous Semiconductors and Liquid Metals.- Properties of Localized States in Disordered Materials.- 7. Banquet Speech.- Are There Cults of Theoreticians?.- 8. Symposium Summary.- Summary and Concluding Remarks.- List of Contributors.