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排序方式: 共有211条查询结果,搜索用时 15 毫秒
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Zheng Zhou James McNeely Joshua Greenough Zheng Wei Haixiang Han Mathieu Rouzires Andrey Yu. Rogachev Rodolphe Clrac Marina A. Petrukhina 《Chemical science》2022,13(13):3864
The synthesis of a novel family of homoleptic COT-based heterotrimetallic self-assemblies bearing the formula [LnKCa(COT)3(THF)3] (Ln(iii) = Gd, Tb, Dy, Ho, Er, Tm, and Yb) is reported followed by their X-ray crystallographic and magnetic characterization. All crystals conform to the monoclinic P21/c space group with a slight compression of the unit cell from 3396.4(2) Å3 to 3373.2(4) Å3 along the series. All complexes exhibit a triple-decker structure having the Ln(iii) and K(i) ions sandwiched by three COT2− ligands with an end-bound {Ca2+(THF)3} moiety to form a non-linear (153.5°) arrangement of three different metals. The COT2− ligands act in a η8-mode with respect to all metal centers. A detailed structural comparison of this unique set of heterotrimetallic complexes has revealed consistent trends along the series. From Gd to Yb, the Ln to ring-centroid distance decreases from 1.961(3) Å to 1.827(2) Å. In contrast, the separation of K(i) and Ca(ii) ions from the COT-centroid (2.443(3) and 1.914(3) Å, respectively) is not affected by the change of Ln(iii) ions. The magnetic property investigation of the [LnKCa(COT)3(THF)3] series (Ln(iii) = Gd, Tb, Dy, Ho, Er, and Tm) reveals that the Dy, Er, and Tm complexes display slow relaxation of their magnetization, in other words, single-molecule magnet (SMM) properties. This behaviour is dominated by thermally activated (Orbach-like) and quantum tunneling processes for [DyKCa(COT)3(THF)3] in contrast to [ErKCa(COT)3(THF)3], in which the thermally activated and Raman processes appear to be relevant. Details of the electronic structures and magnetic properties of these complexes are further clarified with the help of DFT and ab initio theoretical calculations.A new class of heterotrimetallic COT-based self-assemblies accommodates metals from groups I–III in three different oxidation states and enables tuning of electronic and magnetic properties. 相似文献
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The effects of a strong magnetic field on superconducting Nb and MoGe nanowires with diameter approximately 10 nm have been studied. We have found that the Langer-Ambegaokar-McCumber-Halperin (LAMH) theory of thermally activated phase slips is applicable in a wide range of magnetic fields and describes well the temperature dependence of the wire resistance, over 11 orders of magnitude. The field dependence of the critical temperature, T(c), extracted from the LAMH fits is in good quantitative agreement with the theory of pair-breaking perturbations that takes into account both spin and orbital contributions. The extracted spin-orbit scattering time agrees with an estimate tau(s.o.) approximately tau(variant Planck's over 2pic/Ze(2))(4), where tau is the elastic scattering time and Z is the atomic number. 相似文献
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Size effect in the titanium/diamond‐like carbon bilayer films: effect of relative thickness on their structure and mechanical properties
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B. Zhou Z. Liu A.V. Rogachev D.G. Piliptsou B. Tang 《Surface and interface analysis : SIA》2017,49(1):47-54
Titanium/diamond‐like carbon (Ti/DLC) bilayer films with different relative thickness were fabricated by direct‐current and pulsed cathode arc plasma method. Microstructure, morphological characteristics, and mechanical properties of the films were investigated in dependence of the thickness of Ti and DLC layers by Raman spectroscopy, atomic force microscopy, Knoop sclerometer, and surface profilometer. Raman spectra of Ti/DLC bilayers show the microstructure evolution (the size and ordering degree of sp2‐hybridized carbon clusters) with varying the thicknesses of Ti interlayer and DLC layer. Nano‐scaled Ti interlayer of 12–20 nm thickness presents the largest size effect. The catalytic effect of the sublayer is most pronounced in the carbon layer of less than 106 nm. In these thickness ranges, the bilayer films possessed the highest micro‐hardness and reactivity between atoms at interface. Internal stress in the bilayer monotonically decreases, with the thickness of Ti interlayer increasing to 30 nm and then becomes stable with the thickness. These results are associated with the occurrence of atomic diffusion process at Ti/C interface, and they are of cardinal significance to optimize the structure and mechanical properties of carbon‐based multilayer films. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
18.
M. M. Barysheva Yu. A. Vainer B. A. Gribkov M. V. Zorina A. E. Pestov D. N. Rogachev N. N. Salashchenko N. I. Chkhalo 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(1):67-72
The abilities of standard methods for rough surface investigation are analyzed in case of supersmooth substrates for multilayered
X-ray optics. The X-ray specular reflection technique is shown to be the most adequate one. X-ray diffuse scattering and AFM
can be applied only in a case of PSD-function calculation and approximation over the entire spectrum range of spatial frequencies. 相似文献
19.
A. I. Kuklin A. D. Rogov Yu. E. Gorshkova P. K. Utrobin Yu. S. Kovalev A. V. Rogachev O. I. Ivankov S. A. Kutuzov D. V. Soloviov V. I. Gordeliy 《Physics of Particles and Nuclei Letters》2011,8(2):119-128
The results of experimental and computer-modeling investigations of neutron spectra and fluxes obtained with cold and thermal
moderators at the IBR-2 reactor (Joint Institute for Nuclear Research (JINR), Dubna) are presented. These studies are for
the YuMO small-angle neutron scattering (SANS) spectrometer (IBR-2 beamline 4). The neutron spectra have been measured for
two methane cold moderators for the standard configuration of the SANS instrument. The data from both moderators under different
conditions of their operation are compared. The ratio of experimentally determined neutron fluxes of cold and thermal moderators
is shown at different wavelengths. Monte Carlo simulations have been carried out to determine the spectra for cold-methane
and thermal moderators. The results of calculations of the ratio of neutron fluxes of cold and thermal moderators at different
wavelengths are demonstrated. In addition, the absorption of neutrons in the air gaps on the way from the moderator to the
investigated sample is presented. SANS with the protein apoferritin was done with both cold methane and a thermal moderator
and the data were compared. The prospects for the use of a cold moderator for a SANS spectrometer at IBR-2 are discussed.
The advantages of using the YuMO spectrometer with a thermal moderator with respect to the tested cold moderator are shown. 相似文献
20.
Pis'menskaya E. B. Rogachev A. S. Kovalev D. Yu. Ponomarev V. I. 《Russian Chemical Bulletin》2000,49(12):1954-1959
The mechanism of formation of copper aluminides in the thermal explosion mode was studied. A molded mixture of copper and aluminum powders was heated to the self-ignition temperature by the radiation of a tungsten heater. The phase transformations were detected by time-resolved X-ray diffraction (TRXRD). The kinetics of heat release due to the chemical reaction was studied by measuring the temperature of the sample. The macrokinetic stages of the process were revealed, and the apparent activation energy of each stage was estimated. 相似文献