A Pariser-Parr-Pople Model Based Study of Optoelectronic Properties of Phenacenes

Abstract: In this paper we present a computational study of linear optical absorption in phenacene class of polyaromatic hydrocarbons. For the purpose, we have employed a correlated-electron methodology based upon configuration-interaction (CI) approach, and the Pariser-Parr-Pople (PPP) $\pi$-electron model Hamiltonian. The molecules studied range from the smallest one with three phenyl rings (phenanthrene) to the largest one with nine phenyl rings. These structures can also be seen as finite-sized hydrogen-passivated armchair graphene nanoribbons of increasing lengths. Our CI calculations reveal that the electron-correlation effects have a profound influence not just on the peak locations, but also on the relative intensity profile of the computed spectra. We also compare our phenacene results with isomeric oligo-acenes, and find that in all the cases former have a wider optical gap than the latter. Our results are found to be in very good agreement with the experiments, where available.