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81.
Unverfehrt L Ströbele M Glaser J Langer T Hoffmann RD Pöttgen R Meyer HJ 《Inorganic chemistry》2011,50(13):6010-6018
The new europium fluoride carbodiimide Eu(4)F(5)(CN(2))(2) was synthesized by solid state reaction from mixtures of EuF(3) and Li(2)(CN(2)) at 700 °C. The crystal structure as refined by single crystal X-ray diffraction (P ?42(1)c, no. 114, a = 16.053(1) ?, c = 6.5150(6) ?, Z = 8) reveals three crystallographically distinct [N═C═N](2-) ions in the structure of mixed-valent Eu(4)F(5)(CN(2))(2). The presence of one Eu(3+) and three Eu(2+) per formula unit Eu(4)F(5)(CN(2))(2) is confirmed by magnetic measurements and (151)Eu-Mo?ssbauer spectroscopy. The arrangement of Eu ions and gravity centers of [NCN](2-) ions in the structure of Eu(4)F(5)(CN(2))(2) follow the motif formed by atoms in the CuAl(2)-type structure. A possible high-symmetry structure of Eu(4)F(5)(CN(2))(2) is discussed on the basis of a group-subgroup scheme. 相似文献
82.
Krüger S Mögel HJ Wahab M Schiller P 《Langmuir : the ACS journal of surfaces and colloids》2011,27(2):646-650
A simple mathematical model for the depletion force between two arbitrarily shaped large convex colloidal particles immersed in a suspension of small spherical particles is proposed. Using differential geometry, the interaction potential is expressed in terms of the mean and Gaussian curvature of the particle surfaces. The accuracy of theoretical results is tested by Monte Carlo simulations for parallel and nonparallel circular cylinders. The agreement between theoretical results and simulated data is very good if the density of the depletion agent is not too high. 相似文献
83.
84.
Transmission characteristics of polarization-dependent refractometer based on a surface long-period grating (SLPG) inscribed in a D-shaped photonic crystal fiber (PCF) are investigated. The birefringence of SLPG produces the separation of transmission spectra for TE and TM polarization modes. We also measure the sensitivities of PCF-based SLPG to temperature and external refractive index change depending on the input polarization states. The SLPG-based sensor exhibits different temperature and ambient index sensitivities corresponding to TE and TM polarization modes. Therefore, the SLPG inscribed in D-shaped PCFs can effectively discriminate temperature and ambient index sensitivities. 相似文献
85.
Koethe TC Hu Z Haverkort MW Schüssler-Langeheine C Venturini F Brookes NB Tjernberg O Reichelt W Hsieh HH Lin HJ Chen CT Tjeng LH 《Physical review letters》2006,97(11):116402
We present a detailed study of the valence and conduction bands of VO2 across the metal-insulator transition using bulk-sensitive photoelectron and O K x-ray absorption spectroscopies. We observe a giant transfer of spectral weight with distinct features that require an explanation which goes beyond the Peierls transition model as well as the standard single-band Hubbard model. Analysis of the symmetry and energies of the bands reveals the decisive role of the V 3d orbital degrees of freedom. Comparison to recent realistic many body calculations shows that much of the k dependence of the self-energy correction can be cast within a dimer model. 相似文献
86.
Wellert S Altmann HJ Richardt A Lapp A Falus P Farago B Hellweg T 《The European physical journal. E, Soft matter》2010,33(3):243-250
In a microemulsion system based on a mixture of nonionic and ionic surfactants the addition of alcohol instead of changing
the temperature was used to tune the curvature of the surfactant interface. The influence of the addition of the short-chain
alcohol 2-propanol in the system water-perchloroethylene-Marlowet IHF-2-propanol is studied using neutron spin-echo spectroscopy.
In contrast to alcohols with long alkyl chains 2-propanol is no strong co-surfactant, but changes the properties of the solvents.
The present contribution focuses on the bicontinuous phase in this system and a quantitative analysis of the obtained neutron
spin-echo data is proposed within the theoretical framework given by Zilman and Granek for amphiphilic membranes. It turns
out that, in addition to the local movements of the surfactant film, also a collective diffusional mode of the bicontinuous
structure has to be taken into account. The presented approach allows to calculate the bending elastic constant k \kappa of the film. The approach is subsequently applied to follow changes of k \kappa as induced by changes of the alcohol concentration. 相似文献
87.
From a reflection measurement in a rectangular microwave billiard with randomly distributed scatterers the scattering and the ordinary fidelity was studied. The position of one of the scatterers is the perturbation parameter. Such perturbations can be considered as local since wave functions are influenced only locally, in contrast to, e.g., the situation where the fidelity decay is caused by the shift of one billiard wall. Using the random-plane-wave conjecture, an analytic expression for the fidelity decay due to the shift of one scatterer has been obtained, yielding an algebraic 1/t decay for long times. A perfect agreement between experiment and theory has been found, including a predicted scaling behavior concerning the dependence of the fidelity decay on the shift distance. The only free parameter has been determined independently from the variance of the level velocities. 相似文献
88.
Steger M Yang A Stavrias N Thewalt ML Riemann H Abrosimov NV Churbanov MF Gusev AV Bulanov AD Kovalev ID Kaliteevskii AK Godisov ON Becker P Pohl HJ 《Physical review letters》2008,100(17):177402
Dramatic reductions of the linewidths of well-known deep centers in 28Si reveal "isotopic fingerprints" of the constituents. The approximately 1014 meV Cu center, thought to be either a Cu pair or an isolated Cu, is shown to contain four Cu atoms, and the approximately 780 meV Ag center is shown to contain four Ag. The approximately 944 meV ;{*}Cu center, thought to be a different configuration of a Cu pair, in fact contains three Cu and one Ag, and a new two-Cu two-Ag center is found. The approximately 735 meV center, previously assigned to Fe, actually contains Au and three Cu. This suggests a family of four-atom (Cu, Ag, Au) centers. 相似文献
89.
Burke SA Ji W Mativetsky JM Topple JM Fostner S Gao HJ Guo H Grütter P 《Physical review letters》2008,100(18):186104
Submonolayer coverages of the molecule 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) deposited on NaCl(001) surfaces were imaged with high resolution noncontact-atomic force microscopy. Two island types were observed: monolayer islands with a p3x3 epitaxy at low coverage and a mixture of these and bulklike crystallites at higher coverage. The transition between the pure monolayer islands and mixed islands occurs at approximately 0.85 ML, corresponding to a complete p3x3 layer. Calculations show the p3x3 epitaxy to be incompatible with a multilayer crystal of PTCDA. Consequently, the growth of additional layers results in an adaptation of the interface structure forcing a dewetting transition. 相似文献
90.
The synthesis and liquid-crystalline properties of 1,5-dioxa- and 1,5-dithiaspiro[5.5]undecane, 7,16-dioxa-dispiro[5.2.5.2]hexadecane and 1,5,10,14-tetraoxa-dispiro[5.2.5.2]hexadecane derivatives are described. The effects of terminal sub-stituents and molecular structure on the liquid-crystalline properties of these materials are discussed. 相似文献