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|Title: ||Local electron correlation treatment in extended multireference calculations: Effect of acceptor-donor substituents on the biradical character of the polycyclic aromatic hydrocarbon heptazethrene|
|Authors: ||Das, Anita|
Krisiloff, David B.
Carter, Emily A.
|Issue Date: ||2017|
|Publisher: ||© American Chemical Society (ACS)|
|Citation: ||DAS, A. ...et al., 2017. Local electron correlation treatment in extended multireference calculations: Effect of acceptor-donor substituents on the biradical character of the polycyclic aromatic hydrocarbon heptazethrene. Journal of Chemical Theory and Computation, 13(6), pp. 2612-2622.|
|Abstract: ||© 2017 American Chemical Society. The implementation of a local correlation (LC) treatment of multireference (MR) configuration interaction approaches within the COLUMBUS program system is reported. The LC treatment is based on the weak pairs approximation of Sæbø and Pulay (Ann. Rev. Phys. Chem. 1993, 44, 213) and a geometrical analysis of Walter et al. (Chem. Phys. Lett. 2001, 346, 177). The removal of simultaneous single excitations out of the weak pairs is based on the reference doubly occupied space only, leading to a straightforward program implementation and a conceptual simplicity in terms of well-defined localized orbitals. Reductions of up to an order of magnitude in the configuration space expansion and in computer time for the Davidson diagonalization step are found. The selection of the active and the virtual orbital spaces is not affected by this procedure. This treatment is successfully applied to the singlet biradical heptazethrene and its different acceptor-donor substituents: 4,12-dicyanoheptazethrene, 4,12-diaminoheptazethrene, and 4-Amino-12-cyanoheptazethrene. Simultaneous insertion of pairs of donor and acceptor groups increases the biradical character; for push-pull substitution, this effect is significantly smaller. In addition, results obtained from spin-corrected unrestricted density functional theory calculations are supported by our MR calculations.|
|Description: ||This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Chemical Theory and Computation, copyright © American Chemical Society after peer review and technical editing by the publisher.
To access the final edited and published work see https://doi.org/10.1021/acs.jctc.7b00156|
|Sponsor: ||This material is based upon work supported by the National Science Foundation under Award nos. CHE-1213263 (H.L.) and CHE-1265700 (E.A.C.), by the Austrian Science Fund (SFB F41, ViCoM) and by the Vienna Scientific Cluster (VSC) Research Center funded by the Austrian Federal Ministry of Science, Research and Economy, bmwfw (F.P.).|
|Version: ||Accepted for publication|
|Publisher Link: ||https://doi.org/10.1021/acs.jctc.7b00156|
|Appears in Collections:||Published Articles (Chemistry)|
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