A major theme of theoretical modeling of large systems is to find a balance between the accuracy of the results and the computational cost. Since chemical problems are often a local phenomenon, a natural idea is to treat the active part at higher level theory and the other parts at lower (less expensive) level of theory. This is actually the main idea of all hybrid methods. Among them, the ONIOM method has been widely applied to the study of the electronic structures and chemical reactions of large systems due to its simplicity and efficiency. However, in the ONIOM scheme, the dangling bonds, resulted from cutting out the high-layer from the low-layer, need to be capped by link atoms, which create an artificial boundary between the regions treated at different theoretical levels. We present an Extended ONIOM scheme derived from Inclusion-Exclusion Principle to surmount the inherent limitations of the ONIOM scheme.

Iterative hybrid scheme for accurate and efficient geometry optimization: An extended ONIOM method

239th National Meeting (2010)

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