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The global reaction route mapping (GRRM) method enabled an automated and a systematic search for routes of chemical reactions on a potential energy surface based on the anharmonic downward distortion following (ADDF) approach Chem. Phys. Lett. 2004, 384, 277. On the other hand, the microiteration technique Mol. Phys. 2006, 104, 701 has been developed for full optimizations of transition state (TS) structures for reactions/transformations in large flexible molecular systems and successfully used in ONIOM(QM:MM) calculations. In the present paper, combining the GRRM method with the microiteration technique, we developed a microiteration-ADDF (μ-ADDF) method for automated and systematic TS exploration of large flexible molecular systems. We showed that the method works well with two test systems, (H2CO)(H2O)100 and Si6(C12H17)6, in the ONIOM(QM:MM) framework. It is noted that the present μ-ADDF method can be used for pure quantum mechanics (QM) or molecular mechanics (MM) systems (without ONIOM) and has been tested successfully in C6H10O pure QM calculations.
Maeda et al. (Fri,) studied this question.