This volume contains the proceedings of a NATO Advanced Study Institute which was held in Alghero, Sardinia, in July 1991. The development of computers in the recent years has lead to the emergence of unconventional ideas aiming at solving old problems. Among these, the possibility of computing directly fluid flows from the trajectories of constituent particles has been much exploited in the last few years: lattice gases cellular automata and more generally Molecular Dynamics have been used to reproduce and study complex flows. Whether or not these methods may someday compete with more traditional approaches is a question which cannot be answered at the present time: it will depend on the new computer architectures as well as on the possibility to develop very simple models to reproduce the most complex phenomena taking place in the approach of fully developed turbulence or plastic flows. In any event, these molecular methods are already used, and sometimes in an applied engineering context, to study strong shock waves, chemistry induced shocks or motion of dislocations in plastic flows, that is in domains where a fully continuum description appears insufficient. The main topic of our Institute was the molecular simulations of fluid flows. The project to hold this Institute was made three years ago, in the summer of 1989 during a NATO workshop in Brussels on the same subject.

The behaviour of many complex materials extends over time- and lengthscales well beyond those that can normally be described using standard molecular dynamics or Monte Carlo simulation techniques. As progress is coming more through refined simulation methods than from increased computer power, this volume is intended as both an introduction and a review of all relevant modern methods that will shape molecular simulation in the forthcoming decade. Written as a set of tutorial reviews, the book will be of use to specialists and nonspecialists alike.

This volume contains the proceedings of a NATO Advanced Study Institute which was held in Alghero, Sardinia, in July 1991. The development of computers in the recent years has lead to the emergence of unconventional ideas aiming at solving old problems. Among these, the possibility of computing directly fluid flows from the trajectories of constituent particles has been much exploited in the last few years: lattice gases cellular automata and more generally Molecular Dynamics have been used to reproduce and study complex flows. Whether or not these methods may someday compete with more traditional approaches is a question which cannot be answered at the present time: it will depend on the new computer architectures as well as on the possibility to develop very simple models to reproduce the most complex phenomena taking place in the approach of fully developed turbulence or plastic flows. In any event, these molecular methods are already used, and sometimes in an applied engineering context, to study strong shock waves, chemistry induced shocks or motion of dislocations in plastic flows, that is in domains where a fully continuum description appears insufficient. The main topic of our Institute was the molecular simulations of fluid flows. The project to hold this Institute was made three years ago, in the summer of 1989 during a NATO workshop in Brussels on the same subject.

This volume contains the proceedings of a workshop which was held in Brussels during the month of August 1989. A strong motivation for organizing this workshop was to bring together people who have been involved in the microscopic simulation of phenomena occuring on "large" space and time scales. Indeed, results obtained in the last years by different groups tend to support the idea that macroscopic behavior already appears in systems small enough so as to be modelled by a collection of interacting particles on a (super) computer. Such an approach is certainly desirable to study situations where no satisfactory phenomenological theory is known to hold, or where solutions of the equations are too hard to obtain numerically. It is also interesting from a more fundamental point of view, namely the investigation of the limits of validity of the macroscopic description itself. The main technique used in bridging the gap between the macro and micro worlds has been the molecular dynamics simulations, that is the numerical solution of the equations of motion of the model particles which constitute the system under study, a gas, a liquid or even a solid. However, this technique is by no means the only one.