000840330 001__ 840330 000840330 005__ 20210129231817.0 000840330 0247_ $$2doi$$a10.1021/acs.jctc.7b00156 000840330 0247_ $$2ISSN$$a1549-9618 000840330 0247_ $$2ISSN$$a1549-9626 000840330 0247_ $$2pmid$$apmid:28441477 000840330 0247_ $$2WOS$$aWOS:000403530100023 000840330 0247_ $$2altmetric$$aaltmetric:19797512 000840330 037__ $$aFZJ-2017-07872 000840330 041__ $$aEnglish 000840330 082__ $$a540 000840330 1001_ $$0P:(DE-HGF)0$$aDas, Anita$$b0 000840330 245__ $$aLocal Electron Correlation Treatment in Extended Multireference Calculations: Effect of Acceptor–Donor Substituents on the Biradical Character of the Polycyclic Aromatic Hydrocarbon Heptazethrene 000840330 260__ $$aWashington, DC$$c2017 000840330 3367_ $$2DRIVER$$aarticle 000840330 3367_ $$2DataCite$$aOutput Types/Journal article 000840330 3367_ $$0PUB:(DE-HGF)16$$2PUB:(DE-HGF)$$aJournal Article$$bjournal$$mjournal$$s1512476674_31843 000840330 3367_ $$2BibTeX$$aARTICLE 000840330 3367_ $$2ORCID$$aJOURNAL_ARTICLE 000840330 3367_ $$00$$2EndNote$$aJournal Article 000840330 520__ $$aThe implementation of a local correlation (LC) treatment of multireference (MR) configuration interaction approaches within the COLUMBUS program system is reported. The LC treatment is based on the weak pairs approximation of Sæbø and Pulay (Ann. Rev. Phys. Chem. 1993, 44, 213) and a geometrical analysis of Walter et al. (Chem. Phys. Lett. 2001, 346, 177). The removal of simultaneous single excitations out of the weak pairs is based on the reference doubly occupied space only, leading to a straightforward program implementation and a conceptual simplicity in terms of well-defined localized orbitals. Reductions of up to an order of magnitude in the configuration space expansion and in computer time for the Davidson diagonalization step are found. The selection of the active and the virtual orbital spaces is not affected by this procedure. This treatment is successfully applied to the singlet biradical heptazethrene and its different acceptor–donor substituents: 4,12-dicyanoheptazethrene, 4,12-diaminoheptazethrene, and 4-amino-12-cyanoheptazethrene. Simultaneous insertion of pairs of donor and acceptor groups increases the biradical character; for push–pull substitution, this effect is significantly smaller. In addition, results obtained from spin-corrected unrestricted density functional theory calculations are supported by our MR calculations. 000840330 536__ $$0G:(DE-HGF)POF3-511$$a511 - Computational Science and Mathematical Methods (POF3-511)$$cPOF3-511$$fPOF III$$x0 000840330 588__ $$aDataset connected to CrossRef 000840330 7001_ $$0P:(DE-Juel1)132204$$aMueller, Thomas$$b1$$eCorresponding author$$ufzj 000840330 7001_ $$0P:(DE-HGF)0$$aPlasser, Felix$$b2 000840330 7001_ $$0P:(DE-HGF)0$$aKrisiloff, David B.$$b3 000840330 7001_ $$00000-0001-7330-7554$$aCarter, Emily A.$$b4 000840330 7001_ $$00000-0002-5656-3975$$aLischka, Hans$$b5$$eCorresponding author 000840330 773__ $$0PERI:(DE-600)2166976-4$$a10.1021/acs.jctc.7b00156$$gVol. 13, no. 6, p. 2612 - 2622$$n6$$p2612 - 2622$$tJournal of chemical theory and computation$$v13$$x1549-9626$$y2017 000840330 8564_ $$uhttps://juser.fz-juelich.de/record/840330/files/acs.jctc.7b00156.pdf$$yRestricted 000840330 8564_ $$uhttps://juser.fz-juelich.de/record/840330/files/acs.jctc.7b00156.gif?subformat=icon$$xicon$$yRestricted 000840330 8564_ $$uhttps://juser.fz-juelich.de/record/840330/files/acs.jctc.7b00156.jpg?subformat=icon-1440$$xicon-1440$$yRestricted 000840330 8564_ $$uhttps://juser.fz-juelich.de/record/840330/files/acs.jctc.7b00156.jpg?subformat=icon-180$$xicon-180$$yRestricted 000840330 8564_ $$uhttps://juser.fz-juelich.de/record/840330/files/acs.jctc.7b00156.jpg?subformat=icon-640$$xicon-640$$yRestricted 000840330 8564_ $$uhttps://juser.fz-juelich.de/record/840330/files/acs.jctc.7b00156.pdf?subformat=pdfa$$xpdfa$$yRestricted 000840330 909CO $$ooai:juser.fz-juelich.de:840330$$pVDB 000840330 9101_ $$0I:(DE-588b)5008462-8$$6P:(DE-Juel1)132204$$aForschungszentrum Jülich$$b1$$kFZJ 000840330 9131_ $$0G:(DE-HGF)POF3-511$$1G:(DE-HGF)POF3-510$$2G:(DE-HGF)POF3-500$$3G:(DE-HGF)POF3$$4G:(DE-HGF)POF$$aDE-HGF$$bKey Technologies$$lSupercomputing & Big Data$$vComputational Science and Mathematical Methods$$x0 000840330 9141_ $$y2017 000840330 915__ $$0StatID:(DE-HGF)0200$$2StatID$$aDBCoverage$$bSCOPUS 000840330 915__ $$0StatID:(DE-HGF)0300$$2StatID$$aDBCoverage$$bMedline 000840330 915__ $$0StatID:(DE-HGF)0100$$2StatID$$aJCR$$bJ CHEM THEORY COMPUT : 2015 000840330 915__ $$0StatID:(DE-HGF)0199$$2StatID$$aDBCoverage$$bThomson Reuters Master Journal List 000840330 915__ $$0StatID:(DE-HGF)0110$$2StatID$$aWoS$$bScience Citation Index 000840330 915__ $$0StatID:(DE-HGF)0150$$2StatID$$aDBCoverage$$bWeb of Science Core Collection 000840330 915__ $$0StatID:(DE-HGF)0111$$2StatID$$aWoS$$bScience Citation Index Expanded 000840330 915__ $$0StatID:(DE-HGF)1150$$2StatID$$aDBCoverage$$bCurrent Contents - Physical, Chemical and Earth Sciences 000840330 915__ $$0StatID:(DE-HGF)9905$$2StatID$$aIF >= 5$$bJ CHEM THEORY COMPUT : 2015 000840330 9201_ $$0I:(DE-Juel1)JSC-20090406$$kJSC$$lJülich Supercomputing Center$$x0 000840330 980__ $$ajournal 000840330 980__ $$aVDB 000840330 980__ $$aI:(DE-Juel1)JSC-20090406 000840330 980__ $$aUNRESTRICTED