Orbital interaction energy decomposition

It is possible to use as the basis functions symmetry-adapted combinations of primitive basis functions. This affords a decomposition of the orbital interaction energy of Eq. [21] according to irreducible representations of the point group... 

Multiple M=P bonding in (OC)5M=PR becomes evident with ADF s bond energy analysis in terms of electrostatic interactions, Pauli repulsion, and orbital interactions from which the a,Ti-separation is obtained using a symmetry decomposition scheme [21]. For singlet (OC)5Cr=PR, which has a BDEst of 40.5 kcal/mol, the a- and n-components are 62.4 and 40.9 kcal/mol, respectively. 

Most recently, Glendening and Streitwicser have decomposed the interaction energy of the water dimer using natural bond orbitals. Their natural energy decomposition analysis (NEDA) combines the normal electrostatic and exchange energies into a single ES term,... 

Decomposition of interaction energies is desired for qualitative chemical analyses of complicated multi-valent interactions in supramolecular aggregates but such a decomposition cannot be uniquely defined within fundamental physical theory. A popular semi-quantitative decomposition method with nice formal features to be mentioned in this context is Weinhold s natural bond orbital (NBO) approach to intermolecular interactions [232, 233]. Comparable is the recently proposed energy decomposition analysis by Mo, Gao and Peyerimhoff [234, 235] which is based on a block-localized wave function. Other energy decomposition schemes proposed are the energy decomposition analysis (EDA) by Kitaura and Morokuma [236] and a similar scheme by Ziegler and Rauk [237]. 

An energy decomposition analysis was also carried out (ADF/PW91 Table 4), and showed, in agreement with the features of the BCP, that the orbital interaction is an important term in the attractive interaction between the two molecules in the dimer, about 25% larger than the electrostatic term. The Pauli repulsion has about the same magnitude as the orbital interaction. The binding energy is only 0.86 kcal mol, and all these values are so small, that this interpretation should be tested with other approaches. 

Fig. 13.10. Graphical representation of the orbital interaction terms of the energy decomposition analysis of TM -(C0)6 given in Table 13.18.

One method that has proven to be particularly useful for the analysis of molecule/surface interactions is the constrained space orbital variation (CSOV) scheme originally proposed by Bagus and Hermann [30,31]. As does the Morokuma scheme, it allows for a decomposition of the total SCF or DFT interaction energy into its different contributions by calculating only energy quantities, and not as do most other decomposition schemes by analyzing electronic densities or wave functions. The CSOV analysis consists of several consecutive steps which can be roughly characterized as follows ... 

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