AB Initio Studies of Transition Metal Systems

Abstract

In the last 20 years ab initio electronic structure calculations on first-row molecules have progressed to a level of accuracy that is capable of pro­ viding new insights into both electronic structure and chemistry. In contrast, theoretical calculations on molecules containing transition metal atoms have proven to be much more difficult, although recent advances in methodology and the availability of fast vector processors have now made it possible to also obtain quantitative information for many molec­ ular systems containing transition metals. Nonetheless, the quantitative description of multiple metal-metal bonding, such as the well-known prob­ lem associated with calculating the dissociation energy and bond length of the II;: state of Cr2, remain a challenge to theory. Because of the many important materials and catalytic applications of the transition metals, there is considerable incentive to develop methods capable not only of accurately describing small systems, but also for modeling larger systems. In this review we discuss many of the features of molecular systems con­ taining transition metals that arise from the participation of the d electrons. We present applications to selected transition metal hydrides, halides, oxides, dimers and trimers. Finally, we discuss recent work on the Ni + H2 system as a model for the dissociation of H2 on a metal surface.