The importance of interfaces in determining the physical properties of technologically important materials — addressed in the Guest Editors' introduction to the articles in this issue — has stimulated theoretical efforts to determine from first principles a detailed understanding of their chemical, electronic, and mechanical properties. Fortunately, this has now been made possible as a result of the dramatic advances in condensed matter theory made in the last decade, driven in large part by new and sophisticated experiments on high-purity materials that have been well and carefully characterized. Particularly in electronic structure, these advances may be attributable directly to the close collaboration of theoretical and experimental researchers. Indeed, the new found ability to apply fundamental theoretical concepts to real materials (rather than to simple model systems) made possible by using the continued rapid development of computer power, has served to fill the increasingly urgent demand of experimentalists for theoretical interpretation of their data. Also, in some cases, these computational efforts can be used to provide data that would be currently impossible or impractical to obtain experimentally. This development has been an essential element in the phenomenal growth in this area of materials science.

More specifically, the advent of accurate self-consistent (local) spin density functional (LSDF) calculations for surfaces, interfaces, and multilayers means that theory is no longer limited to simple, parameter-dependent models. These complex systems are of growing interest because the reduced symmetry, lower coordination number, and availability and role of highly localized surface and interface states offers the possibility of inducing new and exotic phenomena and promotes the possibility of new device applications.