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Modelling the triplet states of the tris(8-hydroxyquinoline) aluminium (Alq3) complex
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.ORCID iD: 0000-0002-1763-9383
(English)Manuscript (preprint) (Other academic)
National Category
Theoretical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-96122OAI: oai:DiVA.org:kth-96122DiVA: diva2:529704
Note
QS 2012Available from: 2012-05-31 Created: 2012-05-31 Last updated: 2012-05-31Bibliographically approved
In thesis
1. Spin-Orbit and Spin-Spin Coupling in the Triplet State
Open this publication in new window or tab >>Spin-Orbit and Spin-Spin Coupling in the Triplet State
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The underlying theory of “Spin” of an electron and its associated inter-actions causing internal fields and spectral shift to bulk-magnetism iswell established now. Our understanding of spin properties is significant andmore useful than ever before. In recent years there seems to be an enormousinterest towards application oriented materials that harness those spin prop-erties. Theoretical simulations remain in a position to “assist or pilot” theexperimental discovery of new materials.In this work, we have outlined available methodologies for spin coupling inmulti-reference and DFT techniques. We have benchmarked multi-referencespin-Hamiltonian computation in isoelectronic diradicals - Trimethylenemethane(TMM) and Oxyallyl. Also with DFT, parameters are predicted with anewly discovered TMM-like stable diradicals, reported to have large positiveexchange interactions. Excellent agreement were obtained and our findingsemphasize that the dipole-dipole interactions alone can predict the splittingof triplet states and that DFT spin procedures hold well in organic species.We have extended our spin-studies to a highly application oriented ma-terial - nanographene. Using our novel spin-parameter arguments we haveexplained the magnetism of graphene. Our studies highlight a few signifi-cant aspects - first there seems to be a size dependency with respect to thespin-Hamiltonian; second, there is a negligible contribution of spin-orbit cou-pling in these systems; third, we give a theoretical account of spin restrictedand unrestricted schemes for the DFT method and their consequences forthe spin and spatial symmetry of the molecules; and, finally, we highlightthe importance of impurities and defects for magnetism in graphene. Wepredict triplet-singlet transitions through linear response TDDFT for thetris(8-hydroxyquinoline) aluminium complex, an organic molecule shown tohave spintronics applications in recent experiments. Our spin studies werein line with those observations and could help to understand the role of thespin-coupling phenomena.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. 67 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2012:17
Keyword
Spin-spin, Spin-Orbit, D and E parameters, ZFS, graphene, TMM, OXA, diradicals, tris(8-hydroxyquinonline) aluminium, magnetic anisotropy, magnetism, triplet
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-95761 (URN)978-91-7501-366-4 (ISBN)
Public defence
2012-06-07, FB42, AlbaNova Universitetscentrum, Stockholm, 14:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council
Note
QC 20120531Available from: 2012-05-31 Created: 2012-05-29 Last updated: 2012-05-31Bibliographically approved

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Ågren, Hans

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