Multi-References Cluster Expansion Theory and an Interaction of Hydrogen Molecule with Palladium

Abstract

A new multi-ref. cluster expansion theory called MR-SAC theory is given. It is exact, unique, and does not include noncummutative operator algebra without imposing a completeness of the multireference space. From test applications, it was confirmed that the theory is a good approxn. of the exact theory not only for ground states but also for quasidegenerate states and excited states. The interaction of H2 with Pd is studied in the Pd-H2 and Pd2-H2 systems as a model of chemisorption of H2 on a metal surface. The SAC and SAC-CI theories are used to investigate the states involved. For the Pd-H2 system a triangular adduct form is a stable geometry. From the study of the Pd2-H2 system, the equil. H2 .dblarw. H{Â}\textperiodcentered + H{Â}\textperiodcentered occurs very smoothly on the metal surface. [on SciFinder(R)]