Chemical bonds energy decomposition

ADF calculates various chemically meaningful terms that add up to the bond energy, with an adaptation of Morokuma s bond-energy decomposition to the Kohn-Sham MO method. The individual terms are chemically intuitive quantities such as electrostatic energy, steric repulsion, Pauli repulsion, and orbital interactions. The latter are symmetry decomposed according to the Ziegler transition-state method. ... 

This mechanism requires binding of metal electrons to the chemisorbed molecule without formation of a chemical bond (oxidation). The work function of the metal must be of medium height if the most favorable activation of the N2O decomposition is desired. The energy of activation on gold ( = 4.71 volts) is 29.0 kcal, but on platinum ( = 5.36 volts) 32.5 kcal., according to Hinshelwood and Prichard (69). The relative increase of the energy of activation (12.1%) from platinum to gold is about the same as that of the work function (13.8%). 

From a chemical standpoint, the decomposition of the energies of the double bonds into the corresponding a and tz components, Ea and En, is important. Unfortunately, this is a conceptual division and these quantities are not quantum-mechanical observables. Thus, approximate methods have been devised to estimate these contributions. 

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