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'Electric field gradient' in keywords Facet   Publication Year 2000  [X]
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2000[X]
1Author    A. C. Junqueira, A. W. Carbonari, J.Mestnik Filho, R. N. SaxenaRequires cookie*
 Title    Electric Field Gradient at Nb Site in the Intermetallic Compounds Nb 3 X (X = AI, In, Si, Ge, Sn) Measured by PAC  
 Abstract    The electric field gradient (efg) at the Nb site in the intermetallic compounds Nb 3 X (X = Al, In, Si, Ge, Sn) was measured by the Perturbed Angular Correlation (PAC) method using the well-known gamma-gamma cascade of 133 -482 keV in lxl Ta from the ß~ decay of 1K1 Hf, substituting approximately 0.1 atom percent of Nb. The PAC results show that V zz drops by nearly 40% when X changes from Al to In, and by about 25% when X changes from Si to Ge and Sn. This behavior is most probably related to the change in the degree of sp hybridization in these compounds. The V zz values of the studied compounds do not follow the well known universal correlation for the efg's in non-cubic metals but the observed trend is well reproduced by results of ab-initio electronic structure calculations. In the case of Nb 3 Al a linear temperature dependence of the quadrupole frequencies was observed in the temperature range of 6.5 to 1210 K. 
  Reference    Z. Naturforsch. 55a, 41—14 (2000); received August 25 1999 
  Published    2000 
  Keywords    Electric Field Gradient, PAC Measurements, Nb-based Alloys, Quadrupole Interactions 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0041.pdf 
 Identifier    ZNA-2000-55a-0041 
 Volume    55 
2Author    P. F. Meier, T. A. Claxton, P. Hüsser, S. Plibersek, E. P. StollRequires cookie*
 Title    Cluster Calculations of Hyperfine Interactions in Superconducting Copper Compounds  
 Abstract    This paper discusses first-principles cluster investigations on the electronic structure of YBa2Cu3Ü7 and La2CuC>4 performed at the University of Zürich. In particular, electric field gradients have been calculated at the copper sites and their dependence on applying uniaxial strain is studied. Magnetic hyperfine interactions have been evaluated from spin-polarized calculations, and the transfer of spin density from neighboring copper ions is explained. An interpretation is given of the nuclear quadrupole resonance spectra in doped La2CuC>4. 
  Reference    Z. Naturforsch. 55a, 247—255 (2000); received August 26 1999 
  Published    2000 
  Keywords    Cluster Calculations, Electric Field Gradients, High-Temperature Superconductors, Hyperfine Fields, Nuclear Quadrupole Resonance 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0247.pdf 
 Identifier    ZNA-2000-55a-0247 
 Volume    55 
3Author    LeonardoA. Errico, Gabriel Fabricius, Mario RenteríaRequires cookie*
 Title    FP-LAPW Study of the EFG at Impurity Sites in Oxides: Cd in Rutile TiO 2  
 Abstract    We report here first-principles determination of the electric-field gradient (EFG) tensor at the Cd im-purity located at cation sites in rutile Ti0 2 . As far as we know, these represent the first ab initio calcu-lations at impurity sites with the FP-LAPW method in oxide systems. We used super-cells to simulate the diluted impurity in the crystal. The free-relaxation process performed in our study shows that the changes in distances of the oxygen nearest-neighbours to the impurity are not isotropic as was suppo-sed in a previous study within the muffin-tin approximation. Our prediction for the EFG component of major absolute value agrees well with the experiment and is opposite in sign and direction if isotropic relaxations are assumed. Our value of the asymmetry parameter r\ also compares very well with the ex-perimental value. 
  Reference    Z. Naturforsch. 55a, 267—270 (2000); received August 26 1999 
  Published    2000 
  Keywords    Electric-Field Gradient, FP-LAPW, Impurity-Induced Lattice Relaxation, Electronic Struc-ture, Ti0 2 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0267.pdf 
 Identifier    ZNA-2000-55a-0267 
 Volume    55 
4Author    M. Rentería, L. A. Errico, A. G. Bibiloni, K. Freitag, F. G. RequejoRequires cookie*
 Title    PAC Identification of Electric-Nuclear-Quadrupole Interactions in Sm-Sesquioxides  
 Abstract    We present Perturbed Angular Correlation (PAC) results of the electric-nuclear quadrupole interaction at lxl Ta located at the nonequivalent cation sites of cubic C-Sm 2 0 3 and monoclinic B-Sm 2 0 3 free of defects. The application of the empirical Cd/Ta correlation found in binary oxides allowed us to correlate the interactions with each site and to identify the single Sm site populated in 111 In-implanted B-Sm 2 0 3 experiments. The preferential site occupation of Cd and Ta in B-Samaria is discussed in terms of the "chemistry" of the probe-atoms. 
  Reference    Z. Naturforsch. 55a, 155—159 (2000); received August 26 1999 
  Published    2000 
  Keywords    Perturbed-Angular Correlations, Electric-Field Gradients, Sm 2 0 3, Rare-earth Semiconductor and Insulator Oxides, lxl Hf-Impurity Implantation 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0155.pdf 
 Identifier    ZNA-2000-55a-0155 
 Volume    55