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This book is the proceedings of the Sixth Battelle Colloquium on the Science of Materials. The Colloquium was devoted to a new field of materials science in which computers are used to conduct the experiments. Although the computer methods used have reached a high degree of sophistication, the underlying principles are relatively straightforward and well understood. The interatomic force laws - a vital input into these computations - however are less well understood. Interatomic Potentials and Simulation of Lattice Defects primarily discusses the validity of a variety of force laws - either from a theoretical point of view or through comparisons of experimental results and those obtained with computer simulation. The format used in previous Battelle Institute Colloquia is followed. The opening session was aimed at providing an overall view of the field of interatomic forces and defect calculations by major contributors. It was led by Dr. G. H. Vineyard, one of the pioneers in this field. The second day was devoted to research papers on theoretical and experimental aspects of interatomic forces. The remaining days were devoted to research papers on computer simulation of the four types of defects: point defects, line defects, surface defects, and volume defects.
This thesis is concerned with establishing a rigorous, modern theory of the stochastic and dissipative forces on crystal defects, which remain poorly understood despite their importance in any temperature dependent micro-structural process such as the ductile to brittle transition or irradiation damage. The author first uses novel molecular dynamics simulations to parameterise an efficient, stochastic and discrete dislocation model that allows access to experimental time and length scales. Simulated trajectories are in excellent agreement with experiment. The author also applies modern methods of multiscale analysis to extract novel bounds on the transport properties of these many body systems. Despite their successes in coarse graining, existing theories are found unable to explain stochastic defect dynamics. To resolve this, the author defines crystal defects through projection operators, without any recourse to elasticity. By rigorous dimensional reduction, explicit analytical forms are derived for the stochastic forces acting on crystal defects, allowing new quantitative insight into the role of thermal fluctuations in crystal plasticity.
This book contains proceedings of an international symposium on Atomistic th Simulation of Materials: Beyond Pair Potentials which was held in Chicago from the 25 th to 30 of September 1988, in conjunction with the ASM World Materials Congress. This symposium was financially supported by the Energy Conversion and Utilization Technology Program of the U. S Department of Energy and by the Air Force Office of Scientific Research. A total of fifty four talks were presented of which twenty one were invited. Atomistic simulations are now common in materials research. Such simulations are currently used to determine the structural and thermodynamic properties of crystalline solids, glasses and liquids. They are of particular importance in studies of crystal defects, interfaces and surfaces since their structures and behavior playa dominant role in most materials properties. The utility of atomistic simulations lies in their ability to provide information on those length scales where continuum theory breaks down and instead complex many body problems have to be solved to understand atomic level structures and processes.
Interatomic Potentials provides information pertinent to the fundamental aspects of the interaction between atoms. This book discusses the theory of interatomic forces or potentials, which deals with the complicated problem of many-body interactions. Organized into 10 chapters, this book begins with an overview of the physical principles behind a range of atomic interactions and show how they can be applied to some atomic problems. This text then examines some of the theories of the atom that employ various approximate methods to simplify the many-body problem and estimate it potential energy. Other chapters consider the application of computer techniques to atomic problems. This book discusses as well the general principles and the particular types of pair interactions based on the pseudopotential method. The final chapter deals with some applications of interatomic potentials. This book is a valuable resource for graduate students, research workers, and teachers. Atomic and solid state physicists will also find this book useful.
Despite the significant progress in the study of point defects in metals, some important problems still do not have unambiguous solutions. One of the most practically important questions relates to equilibrium defect concentrations. There exist two opposite viewpoints: (1) defect contributions to physical properties of metals at high temperatures are small and cannot be separated from the effects of anharmonicity; the equilibrium defect concentrations at the melting points are in the range of 10-4 to 10-3; (2) in many cases, defect contributions to the specific heat of metals are much larger than nonlinear effects of anharmonicity and can be separated without crucial errors; the equilibrium concentrations at the melting points are of the order of 10-3 in low-melting-point metals and 10-2 in high-melting-point metals.This book discusses the experimental results and theoretical considerations favoring each claim. At present, the majority of the scientific community hold the first viewpoint. Regrettably, the data supporting the second viewpoint have never been displayed and discussed together, and the criticism of this viewpoint has never included a detailed analysis. Important arguments supporting this viewpoint have appeared in the last decade. It may turn out that just calorimetric determinations provide the most reliable values of equilibrium defect concentrations in metals. In this book, the main attention is paid to equilibrium point defects in metals and their relation to thermophysical properties of metals. Along with a discussion on experimental data and theoretical estimates now available, some approaches are proposed that seem to be most suitable for settling the question.