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Reported are the syntheses, crystal structure determinations from single-crystal X-ray diffraction, and magnetic properties of two new ternary compounds, Eu11Cd6Sb12 and Eu11Zn6Sb12. Both crystallize with the complex Sr11Cd6Sb12 structure type—monoclinic, space group C2/m (no. 12), Z=2, with unit cell parameters a=31.979(4) Å, b=4.5981(5) Å, c=12.3499(14) Å, β=109.675(1)° for Eu11Zn6Sb12, and a=32.507(2) Å, b=4.7294(3) Å, c=12.4158(8) Å, β=109.972(1)° for Eu11Cd6Sb12. Their crystal structures are best described as made up of polyanionic and ribbons of corner-shared ZnSb4 and CdSb4 tetrahedra and Eu2+ cations. A notable characteristic of these structures is the presence of Sb-Sb interactions, which exist between two tetrahedra from adjacent layers, giving rise to unique channels. Detailed structure analyses shows that similar bonding arrangements are seen in much simpler structure types, such as Ca3AlAs3 and Ca5Ga2As6 and the structure can be rationalized as their intergrowth. Temperature-dependent magnetization measurements indicate that Eu11Cd6Sb12 orders anti-ferromagnetically below 7.5 K, while Eu11Zn6Sb12 does not order down to 5 K. Resistivity measurements confirm that Eu11Cd6Sb12 is poorly metallic, as expected for a Zintl phase. 相似文献
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Saparov SM Pfeifer JR Al-Momani L Portella G de Groot BL Koert U Pohl P 《Physical review letters》2006,96(14):148101
Confinement of water by pore geometry to a one-dimensional file of molecules interacting with the pore alters the diffusion coefficient D(W). Here we report an exponential dependence of D(W) on the number of water positions in the pore. The result is based on measurements of single channel water permeabilities of structurally similar peptidic nanopores of different length. The inconsistency with predictions from continuum or kinetic models indicates that pore occupancy is reduced in single file transport. In longer pores (e.g., in aquaporins) the presence of charged residues increases D(W). 相似文献
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Chris Worley Dr. Aymen Yangui Rachel Roccanova Dr. Mao-Hua Du Dr. Bayrammurad Saparov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(42):9875-9884
Perovskite solar cells have recently enabled power conversion efficiency comparable to established technologies such as silicon and cadmium telluride. Ongoing efforts to improve the stability of halide perovskites in ambient air has yielded promising results. However, the presence of toxic heavy element lead (Pb) remains a major concern requiring further attention. Herein, we report three new Pb-free hybrid organic–inorganic perovskite-type halides based on gold (Au), (CH3NH3)AuBr4⋅H2O ( 1 ), (CH3NH3)AuCl4⋅H2O ( 2 ), and (CH3NH3)AuCl4 ( 3 ). Hydrated compounds 1 and 2 crystallize in a brand-new structure type featuring perovskite-derived 2D layers and 1D chains based on pseudo-octahedral AuX6 building blocks. In contrast, the novel crystal structure of the solvent-free compound 3 shows an exotic non-perovskite quasi-2D layered structure containing edge- and corner-shared AuCl6 octahedra. The use of Au metal instead of Pb results in unprecedented low band gaps below 2.5 eV for single-layered metal chlorides and bromides. Moreover, at room temperature the three compounds show a weak blue emission due to the electronic transition between Au-6s and Au-5d, in agreement with the density function theory (DFT) calculation results. These findings are discussed in the context of viability of Au-based halides as alternatives for Pb-based halides for optoelectronic applications. 相似文献
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A new family of quaternary fluoro-antimonides A(5)Cd(2)Sb(5)F (A = Sr, Ba, Eu) and oxyantimonides Ba(5)Cd(2)Sb(5)O(x) (0.5相似文献
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Different approaches are considered to the application of the spline-collocation method to bending of rectangular plates. The effect of the choice of collocation nodes on the order of accuracy of the method is investigated. Numerical results obtained with different arrangements of collocation points are reported.Institute of Mechanics, Ukrainian Academy of Sciences. Kiev University. Translated from Vychislitel'naya i Prikladnaya Matematika, No. 68, pp. 93–100, 1989. 相似文献
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