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An SCF LCAO MO ground-state wavefunction is presented for the pyrrole molecule. All electrons, σ and π, are considered, and all the necessary many-center integrals are included in this work. The analysis of the wavefunction reveals that there is a strong two-way charge transfer on the nitrogen atom. (This reopens the problem of the validity of π-electron computations, as discussed in the paper.) The lowest π-electron MO is below the highest σ electron. The hybridization of the σ electrons in the carbon and nitrogen atoms is not s1p2, but deviates strongly for the nitrogen atom and slightly for the carbon atoms.
Clementi et al. (Thu,) studied this question.