Energy pattern, charge-transfer

All of the calculations described here use local functionals that do not include exact exchange. The best choice of functional for calculating MCD spectra is still an open question. In our experience, the MCD parameters produced with different local functionals do not vary much (83). The exception to this rule is functionals that are asymptotically correct. Asymptotically correct functionals tend to give excitation energies that differ from those produced by standard local functionals, particularly for Rydberg and charge-transfer transitions. The MCD parameters produced by asymptotically correct functionals tend to follow a similar pattern when compared with results of other local functionals. A few studies have considered hybrid functionals (42,43). This work found that hybrid functionals were superior in some applications. More work in this area is needed. 

The promotion gap is determined by two basic excitations. For -electron pairs, the promotion energy is k-fold singlet—triplet excitation of the A—A dimer, while for mixed-valence cases where the number of electrons exceeds the number of centers (e.g., H3 ) and vice versa, the promotion energy is a charge-transfer excitation, (e.g., from Hr to H2 in H i ). Let us now use the promotion gap quantity to pattern the data concerning delocalized species. 

The second observation is that photochemically induced electron or hole transfer involves high energies and driving forces. Charge transfer patterns that extend into the inverted free energy region, AG°j have indeed been observed. These are accommodated by the following extension of eq.(6-l)... 

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