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Spin-spin coupling in (3)b(2) state of oxyallyl - A comparative study with trimethylenemethane
KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512). (Prof. Hans Ågren, Prof. O. Vahtras)
KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).ORCID iD: 0000-0002-9123-8174
KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).ORCID iD: 0000-0002-1763-9383
2011 (English)In: Computational and Theoretical Chemistry, ISSN 2210-271X, Vol. 963, no 1, 51-54 p.Article in journal (Refereed) Published
Abstract [en]

Internal splittings in the spectra are due to quantized angular momentum field of the molecule or atom, which couples through spin–spin and spin–orbit operators. These operators are subjected to recently observed close lying states of oxyallyl biradical and compared with the iso-electronic structure trimethylenemethane. With the multiconfigurational treatment of spin–spin coupling operator we predict reversal of the splitting parameter Dss of oxyallyl with reference to isoelectronic TMM spectra.

 

Place, publisher, year, edition, pages
2011. Vol. 963, no 1, 51-54 p.
Keyword [en]
Spin–spin, Biradical, Oxyallyl, Trimethylenemethane(TMM)
National Category
Theoretical Chemistry Atom and Molecular Physics and Optics Condensed Matter Physics
Research subject
SRA - E-Science (SeRC)
Identifiers
URN: urn:nbn:se:kth:diva-29589DOI: 10.1016/j.comptc.2010.09.006ISI: 000289649100009Scopus ID: 2-s2.0-79958101545OAI: oai:DiVA.org:kth-29589DiVA: diva2:396442
Funder
Swedish Research CouncilSwedish e‐Science Research Center
Note
QC 20110210. Uppdaterad från submitted till published 20110307Available from: 2011-02-10 Created: 2011-02-10 Last updated: 2012-08-22Bibliographically approved
In thesis
1. Spin-Spin and Spin-Orbit coupling studies of small species and magnetic system
Open this publication in new window or tab >>Spin-Spin and Spin-Orbit coupling studies of small species and magnetic system
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The spin of an electron often misleadingly interpreted as the classical rotationof a particle. The quantum spin distinguishes itself from classicalrotation by possessing quantized states and can be detected by its magneticmoment. The properties of spin and its collective behavior with otherfundamental properties are fascinating in basic sciences. In many aspectsit offers scope for designing new materials by manipulating the ensemblesof spin. In recent years attention towards high density storage devices hasdriven the attention to the fundamental level were quantum physics rules.To understand better design of molecule based storage materials, studies onspin degrees of freedom and their coupling properties can not be neglected.

To account for many body effect of two or more electrons consistent withrelativity, an approximation like the Breit Hamiltonian(BH) is used in modernquantum chemical calculations, which is successful in explaining the splitin the spectra and corresponding properties associated with it. Often differenttactics are involved for a specific level of computations. For example themulti-configurational practice is different from the functional based calculations,and it depends on the size of the system to choose between resourcesand accuracy. As the coupling terms offers extra burden of calculating theintegrals it is literally challenging.

One can readily employ approximations as it suits best for the applicationoriented device computations. The possible methods available in the literatureare presented in chapter 2. The theoretical implementations of couplingfor the multi-reference and density functional method are discussed in detail.The multi-reference method precedes the density functional methodin terms of accuracy and generalizations, however it is inefficient in dealingvery large systems involving many transition elements, which is vital formolecule based magnets as they often possess open shell manifolds. On theother hand existing density functional method exercise perturbations techniqueswhich is extremely specialized for a specific system - highly coupledspins.

The importance of spin-spin coupling(SSC) in organic radical-Oxyallyl(OXA)was systematically studied with different basis sets and compared with asimilar isoelectronic radical(TMM). The method of spin-spin coupling implementationsare also emphasized. Similar coupling studies were carriedivout for the species HCP and NCN along with spin-orbit coupling(SOC).The splitting of the triplet states are in good agreement with experiments

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. viii, 32 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2010:7
Keyword
spin-spin, spin-orbit, biradical, mcscf
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-12353 (URN)978-91-7415-607-2 (ISBN)
Presentation
2010-04-29, FA31, Roslagstullsbacken 21, Albanova, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20110210Available from: 2010-04-12 Created: 2010-04-09 Last updated: 2011-11-23Bibliographically approved
2. 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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