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Big Bang

Michael Bear, Estela Blaisten-Barojas

Atomic and Ion Collisions in Solids and at Surfaces: Theory, Simulation and Applications. Roger Smith, ed. 309 pp. Cambridge University Press, 1997. $69.95.

Encompassing the entire field of particle collisions with surfaces, this edited book has contributions from seven authors. Given the breadth of this field, the authors have combined an extensive overview of several subjects with an interesting combination of useful details.

The book begins by building the theoretical basis for binary-collision theory. This review includes the tools needed to understand current methods and assumptions and provides good comparisons with experimental results. The computer implementation of binary-collision theory in simulation is not straightforward, and the authors discuss the strengths and weaknesses of various numerical strategies. In addition, useful tables of interatomic-potential parameters are provided. Although the derivations are smooth in their completeness, the presentation could have been enhanced by a richer set of references.

Subsequent chapters cover interatomic potentials, energy loss through ion-electron interaction and transport models. There are insightful discussions of the differences between the theoretical construction of potentials using Laplace and Schrödinger equations versus the empirically derived forms. Following a detailed derivation of Firsov's work for low energies, the authors make the reader aware that the basic theories do not explain all relevant phenomena, and, through useful discussions of the Z1 oscillations in electronic stopping, reveal the weaknesses in the Firsov theory. The discussion of transport models covers the forward and backward Boltzmann-transport equations and provides a very theoretical and complete view of the handling of collisions using this method. This material is more mathematically oriented than earlier chapters. Data on ion penetrations and their distribution within the penetration depth from various potentials are compared among themselves. Chapter six explains the methods of deriving the rest distributions of ions in amorphous targets through the use of moments in one and two dimensions. Examples of collision geometries and statistics, such as non-uniform random variables and moment calculations, are reviewed as well. The authors give very helpful information on the construction of distributions using both Pearson and Johnson frequency curves.

In the three final chapters, the authors give a different flavor to the text by concentrating primarily on binary-collision and molecular-dynamic simulations and their implementation methods. They convey insights about techniques that work and those that don't work—as well as some implementation tricks. These chapters cover binary-collision algorithms, molecular dynamics and macroscopic surface-topography techniques. The method of straight paths and discrete events is quite complex, and a myriad of implementations is possible. The genealogy of binary collisions, primarily next-event algorithms, event ordering and nonlinear events is discussed through several possible choices and their trade-offs. Cascade, Monte Carlo and deterministic models are discussed, as are dynamic models, including dose and annealing effects. The discussion of integration algorithms is instructive in its contrast of methods and comments about their usefulness and practicality. The review of constraint dynamics addresses two methods—SHAKE and RATTLE. Indexing and time stepping are reviewed along with methods for handling boundary conditions and lattice effects. Several cellular models of deposition and erosion are discussed in the last chapter, and an overview of continuum models is adequately expanded in a few pages.

In this mosaic presentation of a very broad field, the authors have done an admirable job of identifying the key material in ways that will be useful and interesting to novices as well as experienced professionals. The conclusions at the end of each chapter are very helpful, but a larger set of references would make this a more valuable resource.—Michael Bear and Estela Blaisten-Barojas, Institute for Computational Sciences and Informatics, George Mason University

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