Exact eigenstates of the Pariser-Parr-Pople model for anthracene

Ramasesha, S. ; Galvao, D. S. ; Soos, Z. G. (1993) Exact eigenstates of the Pariser-Parr-Pople model for anthracene Journal of Physical Chemistry, 97 (12). pp. 2823-2829. ISSN 0022-3654

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Official URL: http://pubs.acs.org/doi/abs/10.1021/j100114a002

Related URL: http://dx.doi.org/10.1021/j100114a002

Abstract

The π-electronic structure of anthracene is discussed by combining exact solutions of the Pariser-Parr-Pople (PPP) model and semiempirical PM3 calculations. Symmetry adaptation of the 2.8 million singlet valence-bond (VB) diagrams is explicitly demonstrated for D2h and electron-hole symmetry. Standard PPP parameters provide a comprehensive fit to one- and two-photon anthracene spectra and intensities up to the strong 1 1B3u-absorption at 5.24 eV, the 10th excited state in the dense correlated spectrum, and indicate a reassignment of two-photon absorptions. The singlet-triplet gap and fine-structure constants also agree with experiment. Fully-relaxed PM3 geometries are obtained for the anthracene ground state and for singlet, triplet, and charged bipolarons. The PM3 bond lengths correlate well with PPP bond orders for the idealized structure. Single-determinantal PM3 excitation and relaxation energies for bipolarons are consistent with exact PPP results and contrast all-valence electron with π-electron calculations. Several correlation effects are noted in the rich π-spectra of anthracene in connection with improved PPP modeling of conjugated molecules and polymers.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:39485
Deposited On:13 May 2011 08:24
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