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The structure of regular star-shaped polystyrenes in deuterated toluene with single (C60) and double (C60-C60) branching centers and different numbers of arms (f = 6, 12, 22) has been investigated using small-angle neutron scattering. For functionalities f = 6 and 12, the thermodynamic rigidity and sizes of arms are larger than the corresponding characteristics of the linear polystyrene precursor; however, for f = 22, the situation reverses: the flexibility increases, the arms are compressed, and the radius of gyration of the stars decreases. The stars transform into dense spherical aggregates, the behavior of which is inconsistent with the Benoit and Daoud-Cotton theories for structures with a high functionality and Gaussian arms. This is explained by the competition between the structuring effect of the fullerene branching center on the solvent and by the reverse effect of the arms playing the role of defects in an ordered layer of the solvent around the fullerene. 相似文献
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Gradhand M Fedorov DV Pientka F Zahn P Mertig I Gy?rffy BL 《J Phys Condens Matter》2012,24(21):213202
Recent progress in wave packet dynamics based on the insight of Berry pertaining to adiabatic evolution of quantum systems has led to the need for a new property of a Bloch state, the Berry curvature, to be calculated from first principles. We report here on the response to this challenge by the ab initio community during the past decade. First we give a tutorial introduction of the conceptual developments we mentioned above. Then we describe four methodologies which have been developed for first-principle calculations of the Berry curvature. Finally, to illustrate the significance of the new developments, we report some results of calculations of interesting physical properties such as the anomalous and spin Hall conductivity as well as the anomalous Nernst conductivity and discuss the influence of the Berry curvature on the de Haas-van Alphen oscillation. 相似文献
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We present an analysis of the Hall conductivity σ(xy)(ω,T) in time reversal symmetry breaking states of exotic superconductors. We find that the dichroic signal is nonzero in systems with interband order parameters. This new intrinsic mechanism may explain the Kerr effect observed in strontium ruthenate and possibly other superconductors. We predict coherence factor effects in the temperature dependence of the imaginary part of the ac Hall conductivity Imσ(xy)(ω,T), which can be tested experimentally. 相似文献
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Zuzana Bujdo?ová Katarína Gy?ryová Dagmar Mudroňová Daniela Hudecová Jana Ková?ová 《Journal of Thermal Analysis and Calorimetry》2012,110(1):167-176
New zinc(II) 4- and 5-chlorosalicylate complexes of general formula [Zn(X-sal)2(L) n (H2O) x ] (where X-sal?=?4-Clsalicylate, 5-Clsalicylate; L?=?N,N-diethylnicotinamide, isonicotinamide, theophylline; n?=?1, 2; x?=?0, 1, 2, 4) were prepared. The complexes were determined by elemental analysis and characterised by infrared spectroscopy. The thermal behaviour of the complexes was studied by simultaneous TG, DTG and DTA methods under dynamic air conditions. The thermal decomposition is a multi-step process. In the first step of the thermal decomposition, water is released in hydrated compounds. The anhydrous compounds start to decompose by the release of organic ligand, followed by chlorosalicylic acid, chlorophenol and carbon monoxide. The final solid product of the thermal decomposition is zinc oxide. The volatile products of the thermal decomposition were determined by mass spectrometry. The antimicrobial activities of the complexes were evaluated against selected pathogen and probiotic bacteria, yeasts and fungi strains. Bioactivities of the tested compounds are different against bacteria, yeasts and filamentous fungi. It was found that bacteria were more sensitive to the studied zinc(II) complex compounds than yeasts or filamentous fungi. 相似文献
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