Correlation effects in the PPP model of alternant π-electronic systems: two-point Padé approximant approach
✍ Scribed by J. ČÍŽek; A. Pellégatti; J. Paldus
- Publisher
- John Wiley and Sons
- Year
- 1975
- Tongue
- English
- Weight
- 955 KB
- Volume
- 9
- Category
- Article
- ISSN
- 0020-7608
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✦ Synopsis
Abstract
A general procedure, based on the two‐point Padé approximant technique, is formulated, enabling an interpolation of the low‐lying energy levels of the PPP (Pariser–Parr–Pople) Hamiltonian over the divergency gap separating the asymptotic perturbation expansions in both strongly and weakly correlated limits. The methods for the determination of the first few terms of the perturbation expansions in both limits are also briefly outlined. The procedure is applied to the five lowest singlet energy levels of the PPP model of the benzene molecule and the results are compared with the exact solutions for this model. The advantages as well as the shortcoming of this approach are pointed out and illustrated on the model calculation for benzene. The applicability of this technique to larger π‐electronic systems is discussed and a feasible procedure for its implementation is formulated.