Elementary Physicochemical Processes On Solid Surfaces

vi industrial process or a class of catalysts forms the basis of other books, with information on: fundamental science of the topic, the use of the pro cess or catalysts, and engineering aspects. Single topics in catalysis are also treated in the series, with books giving the theory of the underlying science, and relating it to catalytic practice. We believe that this approach is giving a collection of volumes that is of value to both academic and industrial workers. The series editors welcome comments on the series and suggestions of topics for future volumes. Martyn Twigg Michael Spencer Billingham and Cardiff Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . 1 . . . . . . . . Chapter 1. Vibrational Relaxation of Adsorbed Particles . . . .. . 5 1.1. General Approach to Describing Vibrational Relaxation ..... 5 1.2. Phonon Mechanism of Relaxation .................... 8 1.2.1. Relationship between the Simple Perturbation Theory and the Adiabatic Approximation .. . . . . . . . . . .. . . 9 . 1.2.2. One-Mode Approximation .................. . .. 11 1.2.3. Relaxation Caused by Correlation Potential Proportional to Displacement of Adsorbed Particle from Equilibrium ........................... 12 1.2.4. Relaxation Caused by Correlation Potential Proportional to Displacement of Surface Atom from Equilibrium ........................... 14 1.2.5. Results and Discussion ....................... 15 1.3. Vibrational Relaxation via Interaction with Conduction Electrons . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 18 . . . . . . . . . 1.3.1. Dipole Approximation ......... '.' . . . . . . . . .. . . 18 .

When we see a jumbo jet at the airport, we sometimes wonder how such a huge, heavy plane can fly high in the sky. To the extent that we think in a static way, it is certainly not understandable. In such a manner, dynamics yields behavior quite different from statics. When we want to prepare an iron nitride, for example, one of the most orthodox ways is to put iron in a nitrogen atmosphere under pressures higher than the dissociation pressure of the iron nitride at temperatures sufficiently high to let the nitrogen penetrate into the bulk iron. This is the way thermodynamics tells us to proceed, which requires an elaborate, expensive high-pressure apparatus, sophisticated techniques, and great efforts. However, if we flow ammonia over the iron, even under low pressures, we can easily prepare the nitride-provided the hydrogen pressure is sufficiently low. Since the nitrogen desorption rate is the determining step of the ammonia decomposition on the iron surface, the virtual pressure of nitrogen at the surface can reach an extremely high level (as is generally accepted) because, in such a dynamic system, the driving force of the ammonia decomposition reaction pushes the nitrogen into the bulk iron to form the nitride. Thus, dynamics is an approach considerably different from statics.

"Spillover and Mobility of Species and Solid Surfaces" collects the papers which were presented at the Fifth International Conference Spillover, either as oral or poster contributions, as well as the summaries of the invited lectures. This congress and its publication in the Studies on Surface Science and Catalysis series follow the tradition of previous conferences on spillover, initiated in Lyon, 1983, and continued in Leipzig, 1989, Kyoto 1993 and Dalian, 1997. For the fifth conference, held in S.L. el Escorial (Madrid), the organising committee has attempted to compile representative contributions which illustrate the advances in understanding the spillover phenomenon since 1997. Spillover is a process taking place during the interface of gas reactant molecules (mainly hydrogen and oxygen) on solid surfaces. However, different contributions to the more general area of the chemistry at surfaces, related with the mobility and migration of species, diffusion through membranes, fuel cell catalysts, etc., have also been included. In fact the title of the present volume summarizes this attempt to extend the conference topics towards dynamics at surfaces. Among the 70 contributions received, the 56 accepted papers were selected on the basis of the reports of at least two international reviewers, according to standards comparable to those applied for other specialised journals. These papers are from 21 different countries.

This book comprises the proceedings of a NATO sponsored Advanced Research Workshop held from 1st November to 6th November 1992 in the delightful Chateau de Florans, Bedoin, Vaucluse, France and entitled 'Elementary Reaction Steps in Heterogeneous Catalysis. ' The organisers are grateful to the Science Committee of NATO for their support of this meeting. This is believed to be the first wide ranging NATO ARW in the field of heterogeneous catalysis for 20 years, following a previous venture organised in Sardinia by Basolo and Burwell, of Northwestern University, Illinois, USA [1]. This volume collects the lecture presentations and reports on the lively Panel discussions. The idea for the meeting evolved from a series of International Symposia on Quantum Chemistry and Mechanism in Heterogeneous Catalysis. The first of these was held in Lyon, France in 1986, the second in Krakow, Poland in 1988 and the third in Berkeley, California in 1990. The organising committee of the present meeting was Bernard Bigot, France, Tony Farragher, Netherlands, Richard Joyner, UK, Mme. Danielle Olivier, France, and Rutger van Santen, Netherlands, (Chairman). We wish to thank all members of the committee but in particular Bernard Bigot, who undertook the very extensive work involved in the local organisation with consummate skill and made our stay in Provence a great pleasure. Bernard Bigot's secretary, Mme. Marie-Noelle Coscat and Richard Joyner's secretary, Mrs. Pat Gibbs, also deserve our considerable thanks. There were fifty-four participants from eleven countries.

As materials research focuses into finding ways to control the growth of atomic scale structures, there is correspondingly increasing emphasis on to the problem of surface diffusion. Clearly surface diffusion is the key process, which determines how atoms move on the surface. Controlling this motion can lead to the easy fabrication of well-controlled nanostructures broadening the present possibilities in nanotechnology. The paradigm of surface diffusion has outgrown its standard textbook description as a random walk on a rigid substrate. In real systems for more complex situations are encountered: interacting atoms are commonly present on the surface with their motions highly correlated, different phases form on the surface with different dynamics, large concentration gradients drive the system far away from the linear response regime, rich metastable structures form as a result of balanced interplay between different kinetic processes, substrate relaxation can change the energy landscape and the diffusion barriers, etc. The motivation behind this ARW was to bring together the international community working on these problems. We felt that the large number of researchers, new results, and well-formulated open questions in this area require some form of integration in a single forum. The ARW and the upcoming proceedings book with papers by the majority of the participants has provided this forum. The meeting was not planned as a continuation of the earlier NATO ASI in Rhodes in 1996, although several people have participated in both meetings.

In 2001 Wyn Roberts celebrated both his 70th birthday and 50 years of working in surface science, to use the term "surface science" in its broadest meaning. This book aims to mark the anniversary with a contribution of lasting value, something more than the usual festschrift issue of a relevant journal. The book is divided into three sections: Surface Science, Model Catalysts and Catalysis, topics in which Wyn has always had interests. The authors for each chapter were chosen from some of the many eminent scientists who have worked with Wyn in various ways and are all internationally acknowledged as leaders in their field. The authors have produced authoritative reviews of their own specialties which together result in a book with an unrivalled combination of breadth and depth exploring the most recent developments in surface chemistry and catalysis.

This book covers the physics and chemistry of surfaces. The scope includes the structure, thermodynamics, and mobility of clean surfaces, as well as the interaction of gas molecules with solid surfaces. The energetic particle interactions that are the basis for the majority of techniques developed to reveal the structure and chemistry of surfaces are explored including auger electron spectroscopy, photoelectron spectroscopy, inelastic scattering of electrons and ions, low energy electron diffraction, scanning probe microscopy, and interfacial segregation. Crystal nucleation and growth are also considered. Principles such as adsorption, desorption and reactions between adsorbates are examined, with coverage also of new developments in the growth of epitaxial, and Langmuir-Blodgett films, as well as treatment of the etching of surfaces. Modern analytical techniques and applications to thin films and nanostructures are included. The latest in-depth research from around the world is presented.

Kinetic Monte Carlo (kMC) simulations still represent a quite new area of research, with a rapidly growing number of publications. Broadly speaking, kMC can be applied to any system describable as a set of minima of a potential-energy surface, the evolution of which will then be regarded as hops from one minimum to a neighboring one. The hops in kMC are modeled as stochastic processes and the algorithms use random numbers to determine at which times the hops occur and to which neighboring minimum they go. Sometimes this approach is also called dynamic MC or Stochastic Simulation Algorithm, in particular when it is applied to solving macroscopic rate equations. This book has two objectives. First, it is a primer on the kMC method (predominantly using the lattice-gas model) and thus much of the book will also be useful for applications other than to surface reactions. Second, it is intended to teach the reader what can be learned from kMC simulations of surface reaction kinetics. With these goals in mind, the present text is conceived as a self-contained introduction for students and non-specialist researchers alike who are interested in entering the field and learning about the topic from scratch.