Phase stability and grain boundary structure in the Cu-Bi system

Abstract

Cu-Bi system is a model system for studies of interfacial phenomena, such as segregation and segregation induced faceting. In previous studies it was found that there is a strong preference for Σ = 3}111{-}111{ type facets, and their atomic structure was successfully resolved by combining high-resolution electron microscopy and computer simulation using Finnis-Sinclair type interatomic potential. The resolved grain-boundary structure was examined usingab initio full-potential linear muffin-tin orbital method by calculating formation enthalpies of several (hypothetical) Cu-Bi compounds under pressure. It was found that there is no driving force for the ordered alloy formed at the boundary to grow into a three-dimensional phase and thus specific interfacial phases are formed in this system. The range of applicability of Finnis-Sinclair potential used in the previous studies was also investigated by comparison withab initio calculations, and it was shown that the potential is entirely appropriate when Cu concentration is higher than about 66 at. %. In those cases the Cu-Bi system exhibits metallic behavior.