Morokuma partitioning

Morokuma Partitioning of the Hartree-Fock Interaction Energy... 

An alternative decomposition, due to K. Morokuma, partitions the interaction energy into five terms. ... 

Figure 2-2. The three-layer partition (B3LYP AM1 Amber) used in the recent test (Adapted from Morokuma et at. [11]. Reprinted with permission. Copyright 2006 American Chemical Society.)...

In order to leam more about the nature of the intermolecular forces we will start with partitioning of the total molecular energy, AE, into individual contri butions, which are as close as possible to those we defined in intermolecular perturbation theory. Attempts to split AE into suitable parts were undertaken independently by several groups 83-85>. The most detailed scheme of energy partitioning within the framework of MO theory was proposed by Morokuma 85> and his definitions are discussed here ). This analysis starts from antisymmetrized wave functions of the isolated molecules, a and 3, as well as from the complete Hamiltonian of the interacting complex AB. Four different approximative wave functions are used to describe the whole system ... 

KM Kitaura-Morokuma means of partitioning the total interaction energy of a given complex. 

We may now introduce a phenomenological partition of W(M/S). The analogy of W(M/S) with the few body intermolecular AE, extensively studied in QM models, could suggest the use of one of the numerous AE decompositions available in literature. In the past we used, with good results, the following partition (Kitaura and Morokuma, 1976) ... 

The idea of partitioning is that in the course of an ab initio calculation, different elements can be extracted and/or isolated. At the most basic level, this serves as a means of interpreting ab initio energetics more so than a distinct means for obtaining the energetics. Morokuma [123 125] and Kollman [126] devised the key computational strategies to extract from ab initio calculations the contributions that could be associated with the different elements of noncovalent weak interaction. One immediate outcome was the confirmation that electrical... 

Fundamental support for the d correction was expressed by Morokuma et who observed that in energy-partitioned SCF calculations the term became excessive for basis sets subject to large BSSE. They argued that a virtuals-only scheme is the proper one to correct for this. It was noted that the virtuals of the ghost to be included should really be those of the counterpoise-corrected instead of the isolated ghost. This recipe is difficult to implement. However, in their example the difference from the simple recipe was extremely small. Similarly. Hayes and Stone state that, while only the virtuals of the partner are available in their non-orthogonal second-order perturbation theory, the occupied orbitals may become available in higher orders. 

Where Hq is the Hamiltonian of the QM regiort, the one of the MM region and Hqmimm Hamiltonian corttaining the interactions between the two parts. Most of the QM/MM methods use this additive partition of the Hamiltoniaa However, a very famous method (ONIOM) developed by Morokuma [48] use a subtractive partition ... 

Figure 4 A schematic diagram of the ONIOM model of Morokuma and co-workers [28]. The system is partitioned into three regions and link atoms are added to saturate bonds broken by the partitioning.

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