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1993 (3)
1989 (1)
1Author    D. Siebert, J. Dahlem, S. Fiechter, A. HartmannRequires cookie*
 Abstract    Synthetic pyrite crystals doped with halogen (CI, Br) or manganese (Mn) were investigated by ESR at 78 K with an X-band spectrometer and a TE102 cavity with lOOkc field modulation. The crystals were preferably measured with the directions <100>, <110), and <111) parallel to the static magnetic field H0. The ESR spectrum of Mn-doped crystals showed a sextet which can be explained by a spin-Hamiltonian for an electron spin S = 1/2 in interaction with the nuclear spin / = 5/2 of the Mn nucleus for axial symmetry. Due to the observed spin and due to the orientation of the paramagnetic centers the spectra were assigned to Mn2+ in the low spin state which resides on cation site in the FeS-, lattice. In halogen-doped crystals four pairs of lines can be interpreted by the interaction of the two isotopes of / = 3/2, 79Br, 81 Br and 35C1, 37C1, respectively, with an electron spin S — 1/2. According to the observed symmetry of the ESR signals the paramagnetic centers can be explained as (S-X)2~ radicals (X = CI, Br) which substitute for the (S2)2~ dumb-bells of pyrite. All crystals evoked extremely narrow ESR lines, especially the halogen-doped crystals with linewidths down to 0.03 mT. Excellent agreement between measured and calculated spectra up to the finest details has been obtained. A n E S R In v e s tig a tio n o f S y n th e tic P y r ite C r y s ta ls 
  Reference    Z. Naturforsch. 44a, 59—66 (1989); received November 12 1988 
  Published    1989 
  Keywords    Pyrite, ESR anorganic radicals, hyperfine coupling, spin densities 
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 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0059.pdf 
 Identifier    ZNA-1989-44a-0059 
 Volume    44 
2Author    Jiahu Wang, VedeneH. SmithRequires cookie*
 Title    Ab initio Study of the Spin Density of Nitroxide Radicals  
 Abstract    The spin densities of the nitroxides H 2 NO, (CH 3)HNO and (CH 3) 2 NO have been studied by iterative CI methods. Calculations at different geometries with various basis sets were performed. It is found that the spin distribution is delocalized within the N-O group, and substitution of the hydrogen atoms on the nitroxyl group by methyl groups changes the spin distribution significantly. Electron correlation, as well as the basis-set quality, plays an important role for the fluctuation of spin populations in the nitroxide radicals. It has been found that the spin density map can be predicted fairly well when correlation was included at certain levels and reasonable quality basis sets were employed. The spin polarization mechanism has been studied through a core excitation method. The superiority of local-spin-density (LSD) theory over the unrestricted Hartree-Fock (UHF) method in spin property studies is discussed. 
  Reference    Z. Naturforsch. 48a, 109—116 (1993); received July 4 1992 
  Published    1993 
  Keywords    Spin density, Nitroxide radicals, Iterative CI, Spin polarization effect, LDA 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0109.pdf 
 Identifier    ZNA-1993-48a-0109 
 Volume    48 
3Author    J.-X Boucherle, E. Ressouche, J. Schweizer, B. Gillon, P. ReyRequires cookie*
 Title    Spin Densities in Copper-Nitronyl Nitroxide Complexes  
 Abstract    The spin density in two copper-nitronyl nitroxide complexes, viz. bis(hexafluoroacetylacetonato)-(2,4,4,5,5-pentamethyl-l-oxy-imidazoline 3-oxide)-copper(II) and dichloro-bis(2-phenyl-4,4,5,5-tetra-methyl-l-oxy-imidazoline 3-oxide)-copper(II), has been determined by polarised-neutron diffrac-tion. Spin populations and unpaired electron wave functions have been refined. 
  Reference    Z. Naturforsch. 48a, 120—122 (1993); received February 7 1992 
  Published    1993 
  Keywords    Nitronyl nitroxide free radicals, Copper complexes, Polarised neutron diffraction, Spin density 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0120.pdf 
 Identifier    ZNA-1993-48a-0120 
 Volume    48 
4Author    B. N. Figgis, E. S. Kucharski, M. VrtisRequires cookie*
 Title    Spin Transfer through Hydrogen Bonding in [CO(NH 3 ) S (OH 2 )| |Cr(CN) 6 | ?  
 Abstract    A polarised-neutron diffraction experiment on [Co(NH 3) 5 (H 2 0)][Cr(CN) 6 ] shows the unexpected features of spin populations on the cobalt ((0.5(2) e) and the "ammine" hydrogen (0.8(1) e in total) atoms. A local density approximation DV-Xa calculation on a unit that models the molecular geometry in the crystal returns features that are broadly in agreement with the experiment. The calculation also reproduces the major features of a charge density experiment on the complex, including the low (+1.6 e) charges on the ions, in place of the formal ±3 e. 
  Reference    Z. Naturforsch. 48a, 123—126 (1993); received October 14 1991 
  Published    1993 
  Keywords    Spin density, Hydrogen bond, Local density approximation calculation, Charge den-sity, Spin transfer 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0123.pdf 
 Identifier    ZNA-1993-48a-0123 
 Volume    48