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Evaluation of the quasi correlated tight-binding (QCTB) model for describing polyradical character in polycyclic hydrocarbons
journal contributionposted on 2018-03-06, 11:22 authored by Anatoliy V. Luzanov, Felix PlasserFelix Plasser, Anita Das, Hans Lischka
We present a verification and significant algorithmic improvement of the quasi-correlation tightbinding (QCTB) scheme (a H¨uckel-Hubbard-type model mimicking electron correlation) for describing effectively unpaired electrons in the spirit of Head-Gordon’s approach [M. Head-Gordon, Chem. Phys. Lett. 380, 488 (2003)]. For comparison purposes, results based on the high-level ab initio multireference averaged quadratic coupled cluster method previously computed in our works are invoked. In doing so, typical polyaromatic hydrocarbons (polyacenes, periacenes, zethrenes, and the Clar goblet) are studied. The evaluation shows that the QCTB H¨uckel-like scheme extended for electron correlation effects provides a qualitatively and in several cases also quantitatively good picture of the unpairing electrons in formally closed-shell electronic systems. Additionally, fairly large nanographene systems of triangulene structure (C426) and a perforated nanoribbon (C8860) have been treated at QCTB level. Two analytical model problems in the framework of QCTB prove the ability of this approximation to give a correct description of natural orbital occupancy spectra. For the studied QCTB scheme, an efficient algorithm is elaborated, and large-scale calculations of radical characteristics for nanographene networks with thousands of carbon atoms are possible.
This material is based upon work supported by the National Science Foundation under Project No. CHE-1213263, by the Austrian Science Fund (SFB F41, ViCom), and by the VSC Research Center funded by the Austrian Federal Ministry of Science, Research and Economy (BMWFW).
Published inThe Journal of Chemical Physics
Pages064106 - 064106
CitationLUZANOV, A.V. ...et al., 2017. Evaluation of the quasi correlated tight-binding (QCTB) model for describing polyradical character in polycyclic hydrocarbons. The Journal of Chemical Physics, 146: 064106.
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Publisher statementThis work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/
NotesThis paper was accepted for publication in the journal The Journal of Chemical Physics and the definitive published version is available at https://doi.org/10.1063/1.4975196