Natural energy decomposition analysis

A much more sophisticated and thorough analysis of intermolecular interactions is provided by the natural energy decomposition analysis (NEDA) module of the NBO 

Full description of NEDA method and usage involves advanced concepts beyond the scope of the present work. The illustrative applications of NEDA provided in the NBO Manual (p. B-104ff) are quite extensive, and should be consulted before attempting research-level use of this keyword. This discussion provides only a qualitative physical description of NEDA energy components and their evaluation for a simple case requiring only the most primitive form of NEDA keyword input (for default NBO molecular units), namely, 

However, the enthusiastic chemical explorer is encouraged to investigate the many options for alternative dissections of the target supramolecular species and the deeper quanrnm mechanical subtleties of the underlying NEDA mathematical formalism (E. D. Glendening and A. Streitwieser, J. Chem. Phys. 100, 2900, 1994 E. D. Glendening, J. Am. Chem. Soc. 118, 2473, 1996 G. K. Schenter and E. D. Glendening, J. Phys. Chem. 100, 17152, 1996). 

NEDA evaluates AE by first performing separate wavefunction calculations on each monomer A, B (in its geometry in the complex) with the fidl dimer basis set, corresponding to the counterpoise-corrected binding energy (as defined by S. F. Boys and F. Bemardi, Mol. Phys. 19, 553, 1970), namely, 

The key step of NEDA decomposition is to evaluate for each monomer a deformed wavefunction (NPa , constructed from block eigenvectors of 

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Glendening, E. D., Streitwieser, A., 1994, Natural Energy Decomposition Analysis An Energy Partitioning Procedure for Molecular Interactions With Apphcation to Weak Hydrogen Bonding, Strong Ionic, and Moderate Donor-Acceptor Interactions , J. Chem. Phys., 100, 2900. 

Table 1.6 Comparison between Morokuma-Kitaura and natural energy decomposition analysis (NEDA) " . All values in kcal/mol, calculated with 4-3IG basis set. 

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,... 

NED A Natural Energy Decomposition Analysis. A means of decomposing the total... 

In order to obtain more information on the solvation process Yang and Cui performed a so called natural energy decomposition analysis (NEDA) on monomethyl phosphate ester (MMP) solvated in water. They used a supermolecular approach where the solute plus a number of water molecules (up to 34) were treated quantum-mechanically. A further set of water molecules was treated with a force-field model. Their results indicate that there is a substantial charge transfer between the solute and the nearest solvent molecules. The interaction energy due to this transfer was found to amount to some 70-80% of that of the electric interactions. Since MMP forms hydrogen bonds with the water molecules, all results together suggests that for such a system it is important to include the nearest solvent molecules in the quantum-mechanical treatment, whereas a continuum approximation or a force field may not be sufficiently accurate. 

Glendening, E. D. Natural energy decomposition analysis Explicit evaluation of electrostatic and polarization effects with application to aqueous clusters of alkali metal cations and neutrals. / Am. Chem. Soc., 118, 2473-2482, doi 10,1021/ja951834y (1996). 

Glendening, E. D., and Streitwieser, A. [1994], Natural energy decomposition analysis An energy partitioning procedure for molecular Interactions with application to weak hydrogen bonding strong ionic, and moderate donor-acceptor interactions,/ Chem. Phys. 100, pp. 2900-2909. 

HONDO = bond orbital - neglect of differential overlap (SCF-MO) GIAO = gauge-including atomic orbital L = Lewis-type (or localized) LC-BO = linear combination of bond orbitals LCNBO = linear combination of NBOs LMO = localized molecular orbital MSPNBO = maximum spin-paired NBO NBBP = natural bond-bond polarizability NBO = natural bond orbital NCS = natural chemical shielding NEDA = natural energy decomposition analysis NHO = natural hybrid orbital NL = non-Lewis-type (or... 

The natural energy decomposition analysis (the keyword is NEDA) of Glendening and Streitwieser provides a more comprehensive picture of the various energy components contributing to intermolecular interactions. The NEDA decomposition mimics in some ways the older Kitaura-Morokuma analysis, but it avoids the use of non-orthogonal (and exclusion principle-violating) wavefiinctions for the two monomers, with the attendant interpretational ambiguities. 

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