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Zero-field splitting of compact trimethylenemethane analogue radicals with density functional theory
KTH, School of Biotechnology (BIO), Theoretical Chemistry.
2011 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 501, no 4-6, 608-611 p.Article in journal (Refereed) Published
Abstract [en]

This work presents the computation of spin-spin coupling that arise between interactions of spin-centers which eventually leads to zero-field splitting in organic molecules. With DFT implementation spin-spin Hamiltonian is subjected to recently observed compact trimethylenemethane analogue di-radicals -nitroxide-substituted nitronyl nitroxide and iminonitroxide, which exhibits large positive exchange interactions with ZFS at the room temperature. We obtain the parameters defining the ZFS that have an excellent agreement with the experiment, consistent with the perception that spin-orbit coupling contribution to the ZFS is negligible in organic molecule. g-tensor shift also calculated with restricted DFT-linear response formalism (RDFT-LR) and compared with realistic observations.

Place, publisher, year, edition, pages
2011. Vol. 501, no 4-6, 608-611 p.
Keyword [en]
ELECTRONIC G-TENSORS, TRANSITION-METAL-COMPLEXES, AB-INITIO CALCULATIONS, SPIN-ORBIT OPERATORS, KOHN-SHAM THEORY, RESPONSE THEORY, PARAMETERS
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-31359DOI: 10.1016/j.cplett.2010.11.068ISI: 000285829300087Scopus ID: 2-s2.0-78650842621OAI: oai:DiVA.org:kth-31359DiVA: diva2:404355
Note
QC 20110316Available from: 2011-03-16 Created: 2011-03-14 Last updated: 2017-12-11Bibliographically 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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