IMOMM methodology

Woo, T. K. Cavallo, L. Ziegler, T. Implementation of the IMOMM methodology for performing combined QM/MM molecnlar dynamics simulations and frequency calculations. Theor. Chem. Acc. 1998,100, 307-313. 

Subsequently, Humbel, Sieber, and Morokuma (1996) generalized the IMOMM optuniza-tion scheme to the case where two different levels of QM theory were used instead of a QM/MM approach, and Svensson, Humbel, and Morokuma (1996) examined the relative efficacy of different combinations of levels for prototype problems. Corchado and Truhlar (1998) later proposed a refinement of that methodology to improve computed vibrational frequencies and Rickard et al. (2003) showed that a combination of MP2 and HF theories permits the calculation of high-quality NMR chemical shifts within the high-level system. 

The situation for transition metal chemistry has been somehow different because, while the description of the electronic effects from the MM region may not be that important, the handling of covalent connections between the QM and MM regions is critical. The methods that have been most successful in handling this situation have been the closely related IMOMM [11] and ONIOM [12, 13]. These schemes provide a computationally economical and methodologically robust method of introducing the steric effects of the... 

Despite their relatively recent appearance in 1995, the IMOMM and ONIOM methods have been extremely productive when applied to transition metal chemistry [15]. A substantial amount of publications have been concerned with homogeneous catalysis, and they will be reviewed in this contribution. Other applications to transition metal chemistry, in structure [16, 17] and reactivity [18, 19], will not be treated here. Methodological aspects of the QM/MM approach, in connection with its application to transition metal chemistry, have been reviewed in a number of papers [20-22]. 

The theoretical study of heme groups has become more common in recent years because of the appearance of new methodologies and the increase in computer power. In particular, the application of the IMOMM (Integrated Molecular Orbital Molecular Mechanics), a hybrid Quantum Mechanics/Molecular Mechanics (QM/ MM) scheme, has allowed the accurate study of transition metal systems [140-142]. 

One of the subjects that has taken a good deal of space in methodological discussions of the design of QM/MM methods is the way to deal with the connection between the QM and MM regions when there are chemical bonds across the boundary. In a number of methods, including IMOMM and derived methods, additional link atoms (usually hydrogen) are introduced in the QM calculation... 

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