Three decades of many-body potentials in materials research
Intent of this issue The introduction of physically sound interatomic potential energy functions that go beyond simple pair-additive interactions (e.g., many-body potentials) beginning in the 1980s opened tremendous modeling capabilities that continue to shape new directions and create critical breakthroughs in materials research.  The key to their proven usefulness is a combination of relative accuracy in reproducing important structures (including defects) across a wide range
... material types and their overall computational effi ciency. This combination of features allows atomic simulations that are large enough to explore phenomena such as correlated dynamics associated with plastic fl ow in metals and accurate enough to be compared to specifi c materials and structures. With this capability, continuum concepts can be tested at the atomic scale, experimental results interpreted in new ways, and virtual experiments carried out that are at the forefront of the development of new materials. Our intentions with this issue of MRS Bulletin are to celebrate the rapid succession of many-body potentials that were introduced in the early to mid-1980s, to review the impact that these potentials have had on research carried out by the materials community in general, and to outline where the fi eld is headed in the next three decades. Contributions in this issue are included from some of the original potential developers, from researchers who have made seminal contributions to materials research using these potentials, and from researchers who are at the forefront of developing and applying the next generation of methods. We expect that this "continuum" of modeling concepts and applications will help guide and inspire the next generation of computational materials scientists and engineers as they expand this capability to new and exciting areas of materials research. Brief history of atomic simulation To understand how this fi eld has progressed to its current state and to predict where it is going, it is useful to briefl y review the history of atomic simulation using classical trajectories (see the sidebar). The fi rst reported study using classical trajectories to model a chemical process was published in 1936 by Hirschfelder, Eyring, and Topley. 6 At this point in the development of atomic simulation, the concept of a continuous potential energy hyper-surface over which atoms moved was still relatively new, and they were interested in understanding how to generate useful potential energy surfaces that defi ne atomic motion for chemical reactions and how to best estimate rates from these surfaces. As part of their studies, they used a single, hand-calculated classical trajectory to study the reaction H + H 2 → H 2 + H constrained to a linear confi guration. This reaction was chosen because with only three electrons, it is relatively simple. The linear confi guration was used because it both reduces the number of degrees of freedom that had to be followed and corresponds to the lowest energy barrier for reaction (and hence the confi guration that most contributes to the overall reaction rate). Their potential energy surface was generated from an analytic approximation to a quantum chemical A brief history of atomic simulation as it was used in chemistry, physics, and materials science is presented starting with seminal work by Eyring in the 1930s through to current work and future challenges. This article provides the background and perspective needed to understand the ways in which reactive many-body potentials developed over the last three decades and have impacted materials research. It also explains the way in which this substantial impact on the fi eld has been facilitated by increases in computational resources and traces the development of reactive potentials, which have steadily increased in complexity and sophistication over time. Together with the other contributions in this issue of MRS Bulletin , this article will help guide and inspire the next generation of computational materials scientists and engineers as they build on current capabilities to expand atomic simulation into new and exciting areas of materials research.