ONIOM Our owN n-layered Integrated

ONIOM Our own n-layered integrated molecular orbital molecular mechanics... 

ONIOM Our own N-layered integrated molecular orbital and molecular mechanics method... 

ONIOM - our Own N-layered Integrated molecular Orbital and molecular Mechanics method Morokuma [121, 122]... 

The ONIOM (our own n-layered integrated molecular orbital and molecular mechanics) method is an extension of IMOMO and IMOMM that performs calculations on n different systems using n levels of calculation. Each system and calculation level constitute a layer. The IMOMO and IMOMM methods are versions of ONIOM with n = 2. ONIOM3 is the three-layered version of ONIOM and uses a real system calculated at a low level, an intermediate model system calculated at a medium level, and a small model system calculated at a high level [M. Svensson et al., J. Phys. Chem., 100,19357 (1996)]. 

This article reviews the onion-like multi-layered integration method, ONIOM (our own N-layered integrated molecular orbital and molecular mechanics) method, developed and mainly applied by the group of present authors, for accurate calculations of large molecular systems which cannot be achieved with the standard molecular orbital (MO) or molecular mechanics (MM) methods. 

Three such methods have been proposed by Morokuma and coworkers. The integrated MO + MM (IMOMM) method combines an orbital-based technique with an MM technique. The integrated MO + MO method (IMOMO) integrates two different orbital-based techniques. The our own n-layered integrated MO and MM method (ONIOM) allows for three or more different techniques to be used in successive layers. The acronym ONIOM is often used to refer to all three of these methods since it is a generalization of the technique. 

S. J. Mo, T. Vreven, B. Mennucci, K. Morokuma and J. Tomasi, Theoretical study of the Sn2 reaction of C1-(H20) +CH3C1 using our own n-layered integrated molecular orbitals and molecular mechanics polarizable continuum model method (ONIOM-PCM), Theor. Chem. Acc., Ill (2004) 154-161. 

The ONIOM approach (our Own N-layer Integrated molecular Orbital molecular Mechanics) developed by the Morokuma group takes an alternative approach to hybrid QM/MM. The distinct advantages of the ONIOM approach are that... 

In the case of larger systems, the ONIOM [178,179] (Our Own N-Layered Integrated Molecular Orbital and Molecular Mechanics) procedure is extensively used. That method is based on the portioning of whole system and creation of layers where different levels of theory are applied (see Fig. 2.37). 

---