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Calculation of zero-field splitting and spin selecitvity in the singlet-triplet transitions of small molecules
KTH, School of Biotechnology (BIO), Theoretical Chemistry. (Prof. Hans Ågren)
(English)In: International Journal of Quantum Chemistry, ISSN 0020-7608, E-ISSN 1097-461XArticle in journal (Other academic) Submitted
National Category
Theoretical Chemistry
URN: urn:nbn:se:kth:diva-29590OAI: diva2:396444
QC 20110210Available from: 2011-02-10 Created: 2011-02-10 Last updated: 2011-02-10Bibliographically 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.
Trita-BIO-Report, ISSN 1654-2312 ; 2010:7
spin-spin, spin-orbit, biradical, mcscf
National Category
Theoretical Chemistry
urn:nbn:se:kth:diva-12353 (URN)978-91-7415-607-2 (ISBN)
2010-04-29, FA31, Roslagstullsbacken 21, Albanova, Stockholm, 10:00 (English)
QC 20110210Available from: 2010-04-12 Created: 2010-04-09 Last updated: 2011-11-23Bibliographically approved

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