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

Ramasesha, S and Galvao, DS and Soos, ZG (1993) Exact eigenstates of the Pariser-Parr-Pople model for anthracene. In: Journal of Physical Chemistry, 97 (12). pp. 2823-2829.

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Abstract

The pi-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 B-1(3u)-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 pi-electron calculations. Several correlation effects are noted in the rich pi-spectra of anthracene in connection with improved PPP modeling of conjugated molecules and polymers.

Item Type:	Journal Article
Publication:	Journal of Physical Chemistry
Publisher:	American Chemical Society
Additional Information:	Copyright of this article belongs to American Chemical Society.
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	08 Feb 2011 07:18
Last Modified:	08 Feb 2011 07:18
URI:	http://eprints.iisc.ac.in/id/eprint/35463

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