Electronic Structure And Reactivity Of Metal Surfaces Lectures Presented At A Nato Advanced Study Institute

Imagine that a young physicist would approach a granting agen cy and propose to contribute to heterogeneous catalysis by studying the heat conductivity of gases in contact with a hot filament. How would he be received now? How would he have been treated sixty years ago ? Yet, more than sixty years ago, Irving Langmuir, through his study of heat transfer from a tungsten filament, uncovered most of the fundamental ideas which are used to-day by the scientific com munity in pure and applied heterogeneous catalysis. Through his work with what were for the first time "clean" metal surfaces, Langmuir formulated during a period of a little over ten years un til the early thirties, the concepts of chemisorption, monolayer, adsorption sites, adsorption isotherm, sticking probability, cata lytic mechanisms by way of the interaction between chemisorbed spe cies, behavior of non-uniform surfaces and repulsion between adsor bed dipoles. It is fair to say that many of these ideas constituting the first revolution in surface chemistry have since been refined through thousands of investigations. Countless papers have been pu blished on the subject of the Langmuir adsorption isotherm, the Langmuir catalytic kinetics and the Langmuir site-exclusion adsorp tion kinetics. The refinements have been significant. ThE original concepts in their primitive or amended form are used everyday by catalytic chemists and chemical engineers allover the world in their treatment of experimental data, design of reactors or inven tion of new processes.

We present here the transcripts of lectures and talks which were delivered at the NATO ADVANCED STUDY INSTITUTE "Electrons in Disordered Hetals and at ~~etallic Surfaces" held at the State University of Ghent, Belgium between August 28 and September 9, 1978. The aim of these lectures was to highlight some of the current progress in our understanding of the degenerate electron 'liquid' in an external field which is neither uniform nor periodic. This theme brought together such topics as the electronic structure at metallic surfaces and in random metallic alloys, liquid metals and metallic glasses. As is the case in connection with infinite order ed crystals, the central issues to be discussed were the nature of the electronic spectra, the stability of the various phases and the occurrence of such phenomena as magnetism and supercon ductivity. In the theoretical lectures the emphasis was on detailed rea listic calculations based, more or less, on the density functional approach to the problem of the inhomogeneous electron liquid. How ever, where such calculations were not available, as in the case of magnetism in random alloys and that of metallic glasses, sim pler phenomenological models were used. The theoretical discussions were balanced by reviews of the most promising experimental techniques. Here the stress was on results and their relevance to the fundamental theory. lforeover, the attention had centered on those experiments which probe the electronic structure in the greatest detail.

We present here the transcripts of lectures and talks which were delivered at the NATO ADVANCED STUDY INSTITUTE "Electronic Structure of Complex Systems" held at the State University of Ghent, Belgium during the period July 12-23, 1982. The aim of these lectures was to highlight some of the current progress in our understanding of the electronic structure of com plex systems. A massive leap forward is obtained in bandstructure calculations with the advent of linear methods. The bandtheory also profitted tremendously from the recent developments in the density functional theories for the properties of the interacting electron gas in the presence of an external field of ions. The means of per forming fast bandstructure calculations and the confidence in the underlying potential functions have led in the past five years or so to a wealth of investigations into the electronic properties of elemental solids and compounds. The study of the trends of the electronic structure through families of materials provided invalu able insights for the prediction of new materials. The detailed study of the electronic structure of specific solids was not neglected and our present knowledge of d- and f-metals and metal hydrides was reviewed. For those systems we also investi gated the accuracy of the one electron potentials in fine detail and we complemented this with the study of small clusters of atoms where our calculations are amenable to comparison with the frontiers of quantum chemistry calculations.

Vols. for 1980- issued in three parts: Series, Authors, and Titles.

In the last few years a surprisingly large number of new experimental techniques have been devised to probe, often with great subtlety, into the electronic structures of inorganic substances. Thus in favourable cases one now has the opportunity of locating and assigning electronically excited states over a 1 vast energy range stretching from tens of cm- above the ground 1 6 state up to some 10 cm- • The techniques are extremely dis parate in background, involving (among others) linearly and circularly polarised electromagnetic radiation, electron kinetic energy analysis and neutron scattering. Furthermore, practition ers of many of the techniques may not be aware of how the information which they are obtaining overlaps and complements that obtained by other techniques. The time therefore seemed ripe to bring together a group of experts to survey, for an audience of inorganic chemists, the basic theories and experim ental procedures relevant to the different techniques, and the relations between them. In pursuing this aim we were fortunate in having the very generous financial backing of N. A. T. O. , through their Advanced Study Institutes programme, and the present volume records the substance of lectures given at the Institute which took place at the Inorganic Chemistry Laboratory and St. John's College, Oxford, from 8-18 September 1974.