Multiple cluster model (MCM) for surface reaction systems

Multiple cluster model (MCM) for investigating surface reactions is formula ted. Ln 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 usin g a simple low-level approximation. Therefore, the MCM can properly simulat e the potential energy hypersurface of the surface reaction system with a f easible computational cost. Since there exists no fixed 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 vibration al 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 th e integrated molecular orbital + molecular mechanics (IMOMM), the integrate d molecular orbital + molecular orbital (IMOMO), and ONIOM developed by Mor okuma and co-workers is also presented. (C) 1999 John Wiley & Sons, Inc.