Localized SCF orbitals are obtained by using the self-energy criteria in the framework of semiempirical methods (Pariser-Parr, Pople-Segal). The delocalisation problem is discussed. These localized orbitals (both occupied and virtual) are used for the calculation of the second-order correlation energy. Qualitative and quantitative features are discussed. The use of localized orbitals allows a deep reduction of the significant terms in the correlation energy.
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