Chemical Bonds Outside Metal Surfaces

The problem of molecules interacting with metal surfaces has for a very long time been recognized to be of considerable technological as well as fundamental importance. Thus in the former category, a substantial number of important synthetic reactions for industrial purposes make use of metal surfaces as catalysts. Or again, problems of corrosion of metals are of great practical importance, such as in nuclear-reactor technology [see, for instance, my earlier articles, in: Physics Bulletin, Volume 25, p. 582, Institute of Physics, UK (1974); and in: Physics and Contemporqry Needs (Riazuddin, ed. ), Vol. 1, p. 53, Plenum Press, New York (1977)]. It is therefore of significance to strive to gain a more fundamental understand ing of the atomic, and ultimately the electronic, processes that occur when a molecule is brought into the proximity of a metal surface. The present volume focuses mainly on the theory and concepts involved; however, it is intended for readers in chemistry, physics, and materials science who are not specialists in theory but nevertheless wish to learn more about this truly interdisciplinary area of theoretical science. The aim of the book is to present the way in which valence theory can be synthesized with the understanding of metals that has been gained over the last half century or so. While advanced theory has at times been necessary, is largely presented in an extensive set of Appendixes.

Inhalt

1. Background, Phenomenology, and Motivation.- 1.1. Chemisorption in Ionic and Covalent Limits.- 1.2. Kinetics of Adsorption and Desorption.- 1.3. Thermodynamics of Adsorption.- 1.4. Reaction Mechanisms Outside Surfaces.- 1.5. Case History of Catalytic Hydrogenation of Carbon Monoxide.- 2. Diatomic Molecules.- 2.1. Physisorbed Diatoms with Weil-Defined Cores.- 2.2.1. Physisorbed H2.- 2.3. Interaction Energy: Tight-Binding Model.- 2.4. Molecular Versus Dissociative Adsorption.- 2.5. Detailed Bonding Studies.- 2.6. Electronically Excited States of Chemisorbed Diatoms.- 2.7. Orientation of Molecular Adsorbates.- 2.8. Temperature Effects, and Comparison Between Theory and Experiment.- 3. Conformation and Electronic Structure of Polyatomic Molecules.- 3.1. Conformation of a Water Molecule Outside a Metal Surface.- 3.2. Conformation of NH3 and C2H4 Molecules.- 3.3. Molecular Versus Dissociative Adsorption of NH3 on Transition-Metal Surfaces.- 3.4. Electronic Structure and Conformation of Ethene on Transition- and Noble-Metal Surfaces.- 3.5. Interaction Between Adsorbates.- 3.6. Electronic Excited States of Chemisorbed Polyatomic Molecules.- 4. Dynamics of Adparticles and Neutron Inelastic Scattering.- 4.1. Principles of Neutron Scattering from Adsorbed Molecules.- 4.2. Comparison With Other Surface Techniques.- 4.3. Diffusion Measurements.- 4.4. Theory.- 4.5. Electronic and Vibration-Rotation Spectra of Adsorbed Molecules.- 4.6. Adsorbate Frequency Shifts.- 4.7. Theoretical Framework for Interpreting Neutron Inelastic Scattering From Covered Surfaces.- 4.8. Theory of Surface Diffusion.- 4.9. Vibration Excitation in Molecule-Surface Collisions Due to Temporary Negative Molecular-Ion Formation.- 4.10. Adparticle Dynamics: Kramers' Equation in a Metallic Medium.- 5. MolecularDesorption.- 5.1. Kramers' Theory Generalized to Desorption From Solid Surfaces.- 5.2. Transition-State Theory Applied to Desorption From Solid Surfaces: Ammonia on Ni(111).- 5.3. Microscopic Theories.- 5.4. Quantum-Statistical Theory of Physisorption.- 5.5. Coverage-Dependent Regime.- 5.6. Desorption Induced by Electronic Transitions.- 6. Catalysis.- 6.1. Some Definitions and Concepts.- 6.2. XPS Studies of Desorption and Dissociation Processes.- 6.3. Compensation Effect.- 6.4. Relevance of WoodwardHoffmann Rules to Single-Crystal Catalysts.- 6.5. Electronic Structure Study of a Poisoned Catalyst Surface..- 6.6. Chemical Oscillations.- Appendixes.- 1.1. Surface Characterization Techniques Used to Determine Structure and Composition of Solid Surfaces.- 2.1. Density Matrix and Linear-Response Function of the Infinite-Barrier Model of a Metal Surface.- 2.2. Influence of Fermi-Surface Topology on Asymptotic Displaced-Charge Round Adatoms.- 2.3. Correlation Effects for Hydrogen Chemisorbed on Transition Metals.- 2.4. Lifetimes of Excited States of Molecules Well Outside Metal Surfaces: a Model Calculation.- 3.2. Parametrization of the Tight-Binding Model of Ethene.- 3.3. Parametrization of the Anderson Hamiltonian Describing the ?-Energy Levels of the Free Ethene Molecule.- 4.1. Three-Dimensional Treatment of the Escape of a Brownian Particle From a Well.- 4.2. Dynamics of a Brownian Particle in a Fluid: Derivation of Stochastic Elements.- 4.3. Variational Principle for the Optimum Reaction Coordinate in Diffusion-Controlled Reactions.- 4.4. Anisotropic Screening of an Adatom Near a Metal Surface.- 5.1. Spin Fluctuations and Desorption of Hydrogen From Paramagnetic Metals.- 5.2. Anomalies in Adsorption Equilibrium Near Critical Points of a Substrate.- 6.1.Symmetry Rules Based on the Surface Electronic Structure of Various Platinum Surfaces.- 6.3. Analysis of Rate Equations Describing Chemical Oscillations.- 6.4. Proposed Reaction Sequence for Fischer-Tropsch Synthesis.- 6.5. Dissociative Chemisorption A Primitive Surface Chemical Process.- 6.6. Nonlinear Rate Equations and the Compensation Effect.- Notes Added in Proof.- References.