Multiple cluster model (MCM) for surface reaction systems

Abstract

Multiple cluster model MCM for investigating surface reactions isformulated. In this model the reaction center, where electron correlation effects often play a key role, is described by an accurate high-level approximation, and bulk effects such as the lattice distortion energy are evaluated using a simple low-level approximation. Therefore, the MCM can properly simulate the potential energy hypersurface of the surface reaction system with a feasible computational cost. Since there exists no fixed Ž atom in the MCM, we can rigorously characterize the stationary point the minimum . energy point or the transition state on the potential energy hypersurface by vibrational frequency analysis. The MCM can be applied not only to surface systems, but also to various large systems. A detailed comparison of the MCM with the integrated molecular Ž . orbital q molecular mechanics IMOMM , the integrated molecular orbital q molecular Ž . orbital IMOMO , and ONIOM developed by Morokuma and co-workers is also presented.