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Träfflista för sökning "WFRF:(Delin I.) "

Sökning: WFRF:(Delin I.)

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  • Keshavarz, Samara, et al. (författare)
  • Layer-resolved magnetic exchange interactions of surfaces of late 3d elements Effects of electronic correlations
  • 2015
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - American Physical Society. - 1098-0121. ; 92:16
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the results of an ab initio study of the magnetic properties of Fe, Co, and Ni surfaces. In particular, we discuss their electronic structure and magnetic exchange interactions (J(ij)), as obtained bymeans of a combination of density functional theory and dynamical mean-field theory. All studied systems have a pronounced tendency to ferromagnetism both for bulk and surface atoms. The presence of narrowband surface states is shown to enhance the magnetic moment as well as the exchange couplings. The most interesting results were obtained for the Fe surface where the atoms have a tendency to couple antiferromagnetically with each other. This interaction is relatively small when compared to interlayer ferromagnetic interaction, and it depends strongly on the lattice parameter. Local correlation effects are shown to lead to strong changes of the overall shape of the spectral functions. However, they seem not to play a decisive role in the overall picture of magnetic couplings studied here. We have also investigated the influence of correlations on the spin and orbital moments of bulklike and surface atoms. We found that dynamical correlations in general lead to enhanced values of the orbital moment.
  • Locht, Inka L. M., et al. (författare)
  • Standard model of the rare earths analyzed from the Hubbard I approximation
  • 2016
  • Ingår i: PHYSICAL REVIEW B. - American Physical Society. - 2469-9950. ; 94:8
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work we examine critically the electronic structure of the rare-earth elements by use of the so-called Hubbard I approximation. From the theoretical side all measured features of both occupied and unoccupied states are reproduced, without significant deviations between observations and theory. We also examine cohesive properties like the equilibrium volume and bulk modulus, where we find, in general, a good agreement between theory andmeasurements. In addition, we have reproduced the spin and orbital moments of these elements as they are reflected from measurements of the saturation moment. We have also employed the Hubbard I approximation to extract the interatomic exchange parameters of an effective spin Hamiltonian for the heavy rare earths. We show that the Hubbard I approximation gives results which are consistent with calculations where 4f electrons are treated as core states for Gd. The latter approach was also used to address the series of the heavy/late rare earths. Via Monte Carlo simulations we obtained ordering temperatures which reproduce measurements within about 20%. We have further illustrated the accuracy of these exchange parameters by comparing measured and calculated magnetic configurations for the heavy rare earths and the magnon dispersion for Gd. The Hubbard I approximation is compared to other theories of the electronic structure, and we argue that it is superior. We discuss the relevance of our results in general and how this makes it possible to treat the electronic structure of materials containing rare-earth elements, such as permanent magnets, magnetostrictive compounds, photovoltaics, optical fibers, topological insulators, and molecular magnets.
  • Panda, S. K., et al. (författare)
  • A charge self-consistent LDA plus DMFT study of the spectral properties of hexagonal NiS
  • 2014
  • Ingår i: New Journal of Physics. - 1367-2630 .- 1367-2630. ; 16, s. 093049
  • Tidskriftsartikel (refereegranskat)abstract
    • The electronic structure and spectral properties of hexagonal NiS have been studied in the high temperature paramagnetic phase and low temperature anti-ferromagnetic phase. The calculations have been performed using charge self-consistent density-functional theory in local density approximation combined with dynamical mean-field theory (LDA+DMFT). The photoemission spectra (PES) and optical properties have been computed and compared with the experimental data. Our results show that the dynamical correlation effects are important to understand the spectral and optical properties of NiS. These effects have been analyzed in detail by means of the computed real and imaginary part of the self-energy.
  • Gaber, Flora, et al. (författare)
  • Saliva is one likely source of leukotriene B4 in exhaled breath condensate
  • 2006
  • Ingår i: European Respiratory Journal. - 0903-1936. ; 28:6, s. 1229-35
  • Tidskriftsartikel (refereegranskat)abstract
    • Leukotriene (LT)B4 in exhaled breath condensate (EBC) has been reported to be elevated in airway inflammation. The origin of leukotrienes in EBC is, however, not established. The aims of this study are to measure LTB4 levels in EBC collected in two challenges characterised by a strong neutrophilic airway inflammation and to compare LTB4 levels in EBC with levels in sputum and saliva. LTB4 and alpha-amylase were measured in EBC from 34 healthy subjects exposed in a pig confinement building or to a lipopolysaccharide provocation. These markers were also measured in induced sputum in 11 of the subjects. For comparison, LTB4 and alpha-amylase were measured in saliva from healthy subjects. Only four out of 102 EBC samples had detectable LTB4 (28-100 pg x mL(-1)). alpha-amylase activity was detected in the LTB4-positive samples. In contrast, LTB4 was detected in all examined sputum supernatants in the same study (median 1,190 pg x mL(-1)). The median LTB4 level in saliva was 469 pg x mL(-1). High levels of leukotriene B4 in saliva and the presence of leukotriene B4 in exhaled breath condensate only when alpha-amylase was detected, indicate that leukotriene B4 found in exhaled breath condensate is the result of saliva contamination. As leukotriene B4 was consistently present in sputum supernatants, exhaled breath condensate may be inappropriate for monitoring airway leukotriene B4.
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