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Restricted density functional response theory for open-shell systems
KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
KTH, School of Biotechnology (BIO).
KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).ORCID iD: 0000-0002-9123-8174
2005 (English)In: ADVANCES IN QUANTUM CHEMISTRY, VOL 50: Book Series: ADVANCES IN QUANTUM CHEMISTRY / [ed] Sabin, JR; Brandas, E, SAN DIEGO: ELSEVIER ACADEMIC PRESS INC , 2005, Vol. 50, 271-288 p.Conference paper (Refereed)
Abstract [en]

This work presents development, implementation and applications of density functional theory (DFT) methods for calculation molecular properties of open-shell molecules. The theory of restricted open-shell density functional response theory is briefly summarized and the advantages and disadvantages of a spin-restricted formulation is discussed. Sample calculations are presented and discussed for excitation energies, polarizabilities and ESR spectral parameters: g-tensors and A-tensors (hyperfine coupling constants). For the A-tensors a recent generalization of the restricted-unrestricted approach [Fernandez, et al., J. Chem. Phys. 97 (1992) 3412] has been used. It is found that the additional complexity of spin-restricted methods is motivated by the quality of our results.

Place, publisher, year, edition, pages
SAN DIEGO: ELSEVIER ACADEMIC PRESS INC , 2005. Vol. 50, 271-288 p.
Keyword [en]
hyperfine coupling-constants, polarizable continuum model, hydrocarbon radical cations, electronic g-tensors, hartree-fock, wave-functions, molecules, naphthalene, anthracene, hydrogen
National Category
Physical Chemistry
URN: urn:nbn:se:kth:diva-6178DOI: 10.1016/S0065-3276(05)50013-3ISI: 000235210900015ScopusID: 2-s2.0-33645886942ISBN: 0-12-034850-0OAI: diva2:10811
Conference on Response Theory and Molecular Properties. Sandbjerg Estate, DENMARK. MAY 05-08, 2004
QC 20111013Available from: 2006-09-22 Created: 2006-09-22 Last updated: 2012-03-21Bibliographically approved
In thesis
1. Density functional studies of EPR and NMR parameters of paramagnetic systems
Open this publication in new window or tab >>Density functional studies of EPR and NMR parameters of paramagnetic systems
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Experimental methods based on the magnetic resonance phenomenon belong to the most widely used experimental techniques for investigations of molecular and electronic structure. The difficulty with such experiments, usually a proper interpretation of data obtained from high-resolution spectra, opens new challenges for pure theoretical methods. One of these methods is density functional theory (DFT), that now has an advanced position among a whole variety of computational techniques. This thesis constitutes an effort in this respect, as it presents theory and discusses calculations of electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) parameters of paramagnetic molecules. It is known that the experimental determination of the magnetic resonance parameters of such molecules, especially in the case of NMR, is quite complicated and requires special techniques of spectral detection. On the other hand, paramagnetics play an important role in many areas, such as molecular magnets, active centers in biological systems, and defects in inorganic conductive materials. Therefore, they have spurred great interest among experimentalists, motivating us to facilitate the interpretation of spectral data through theoretical calculations. This thesis describes new methodologies for the determination of magnetic properties of paramagnetic molecules in the framework of DFT, which have been developed in our laboratory, and their applications in calculations of a wide range of molecular systems.

The first two papers of this thesis deal with the theoretical determination of NMRparameters, such as nuclear shielding tensors and chemical shifts, in paramagnetic nitroxides that form core units in molecular magnets. The developed methodology is aimed to realize a high calculational accuracy for these systems. The effects of hydrogen bonding are also described in that context. Our theory for the evaluation of nuclear shielding tensors in paramagnetic molecules is consistent up to second order in the fine structure constant and considers orbital, fully anisotropic dipolar, and isotropic contact contributions to the shielding tensor.

The next projects concern electron paramagnetic resonance. The well-known EPR parameters, such as the g-tensors and the hyperfine coupling constants are explored. Calculations of electronic g-tensors were carried out in the framework of a spin-restricted open-shell Kohn-Sham method combined with the linear response theory recently developed in our laboratory and allowing us to avoid by definition the spin-contamination problem. The inclusion of solvent effects, described by the polarizable continuum model, extends the possibility to treat molecular systems often investigated in solution. For calculations of the hyperfine coupling constants a so-called restricted-unrestricted approach to account for the spin polarization effect has been developed in the context of DFT. To examine the validity of the approximations implicit in this scheme, the neglect ii of singlet operators, a generalized RU methodology was implemented, which includes a fully unrestricted treatment with both singlet and triplet operators. The small magnitude of the changes in hyperfine coupling constants confirms the validity of the original scheme.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 50 p.
spin-restricted DFT, restricted-unrestricted approach, EPR spin Hamiltonian parameters, NMR spin Hamiltonian parameters
National Category
Organic Chemistry
urn:nbn:se:kth:diva-4116 (URN)91-7178-450-0 (ISBN)
Public defence
2006-10-06, FD5, AlbaNova, Stockholm, 10:00
QC 20100923Available from: 2006-09-22 Created: 2006-09-22 Last updated: 2012-03-21Bibliographically approved

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Rinkevicius, Zilvinas ̌Telyatnyk, LyudmylaVahtras, Olav
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