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151.
Eugenia Elzer Dr. Philipp Strobel Volker Weiler Muhammad R. Amin Dr. Peter J. Schmidt Prof. Dr. Alexander Moewes Prof. Dr. Wolfgang Schnick 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(12):e202104121
The nitridoberylloaluminate Ba2[BeAl3N5]:Eu2+ and solid solutions Sr2−xBax[BeAl3N5]:Eu2+ (x=0.5, 1.0, 1.5) were synthesized in a hot isostatic press (HIP) under 50 MPa N2 atmosphere at 1200 °C. Ba2[BeAl3N5]:Eu2+ crystallizes in triclinic space group (no. 2) (Z=2, a=6.1869(10), b=7.1736(13), c=8.0391(14) Å, α=102.754(8), β=112.032(6), γ=104.765(7)°), which was determined from single-crystal X-ray diffraction data. The lattice parameters of the solid solution series have been obtained from Rietveld refinements and show a nearly linear dependence on the atomic ratio Sr : Ba. The electronic properties and the band gaps of M2[BeAl3N5] (M=Sr, Ba) have been investigated by a combination of soft X-ray spectroscopy and density functional theory (DFT) calculations. Upon irradiation with blue light (440–450 nm), the nitridoberylloaluminates exhibit intense orange to red luminescence, which can be tuned between 610 and 656 nm (fwhm=1922–2025 cm−1 (72–87 nm)). In contrast to the usual trend, the substitution of the smaller Sr2+ by larger Ba2+ leads to an inverse-tunable luminescence to higher wavelengths. Low-temperature luminescence measurements have been performed to exclude anomalous emission. 相似文献
152.
A. A. Lavrent’ev B. V. Gabrelyan V. B. Vorzhev I. Ya. Nikiforov O. Yu. Khizhun J. J. Rehr 《Journal of Structural Chemistry》2007,48(3):467-473
The electron energy structure of titanium and hafnium carbide, titanium and solid solutions of TaC0.5N0.5 and Hf0.5Ta0.5C nitride is investigated experimentally (by X-ray and X-ray photoelectron spectroscopy) and theoretically (based on the quantum mechanical calculations in a full multiple scattering approximation, by the program FEFF8 with a self-consistent semirelativistic potential). A good accordance between the calculated curves of the densities of electronic states and the corresponding experimental curves is obtained. The chemical bond features in the investigated compounds and solutions are revealed. 相似文献
153.
Thermal plasma synthesis of transition metal nitrides and alloys 总被引:1,自引:0,他引:1
Applications of arc plasma processing to high-temperature chemistry of Group V nitrides and Si and Ge alloys are studied. The transition metal nitrides -VN, -NbN, and -TaN are directly synthesized in a dc argon-nitrogen plasma from powders of the metals. A large excess of N2 is required to form stoichiometric -VN, while the Nb and Ta can only be synthesized with a substoichiometric N content. In a dc argon plasma the alloys V3Si, VSi2, NbSi2, NbGe2, Cr3Si, and Mo3Si are obtained from powder mixtures of the corresponding elements. The compounds are identified by x-ray diffraction patterns and particle shape and size are studied by electron microscopy. 相似文献
154.
Nitrido Silicates. I. High Temperature Synthesis and Crystal Structure of Ca2Si5N8 Ca2Si5N8 is obtained by reaction of silicon diimide with metallic calcium under nitrogen atmosphere performed in a specially developed high-frequency furnace at temperatures between 1 500 and 1 600°C. Ca2Si5N8 (Cc, a = 1 435.2(3), b = 561.0(1), c = 968.9(2) pm, β = 112.06(3)°, Z = 4, R = 0.023, wR = 0.018) contains Ca2+ ions as well as a three-dimensional covalent network structure of corner-sharing SiN4 tetrahedra. Two sorts of N occur with molar ratio 1:1 which are bonded to two and three Si, respectively. 相似文献
155.
The geometrical and electronic structures of two isomers (1 and2) of the polyhedral boron nitride molecule, B12N12, have been calculated using the MNDO method. Structure1 having the form of a truncated octahedron is more energetically preferable (ΔH
f
0=−128 kcal mol−1) than isomer2, which hasC
6v symmetry. The equilibrium geometries of the N6B6(CH2)6 isomers (3 and4), which simulate fragments of structure2, have been calculated. The stabilization mechanism of the N6 nitrogen cluster (hexaazabenzene) in polyhedral structures is discussed. The parameters calculated for molecules1 and2 have been correlated with the corresponding characteristics of their carbon analogs.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1712–1714, October, 1993. 相似文献
156.
A significant cationic disorder is evidenced on Li3FeN2 prepared through solid-state reaction under controlled atmosphere. This derivative anti fluorite type structure (orthorhombic, space group Ibam, a=4.870(1) Å, b=9.652(1) Å and c=4.789(1) Å), solved first through single crystal X-ray diffraction [7], is usually described by Li+ and Fe+3 ordered distribution in tetrahedral sites formed by the nitrogen network, leading to [FeN4/2]3− edge-sharing tetrahedral chains. From 7Li/6Li Nuclear Magnetic Resonance spectroscopy, 57Fe Mössbauer spectroscopy and powder X-ray and neutron diffraction, we demonstrate that about 4% of lithium sites are filled by iron and about 11% of iron sites are occupied by Li, which can explain the discrepancy within the Gudat's model observed on larger scale solid-state synthesis samples. 相似文献
157.
158.
Dr. Jeongsuk Seo Dr. Hiroshi Nishiyama Dr. Taro Yamada Prof. Kazunari Domen 《Angewandte Chemie (International ed. in English)》2018,57(28):8396-8415
Solar energy is a natural and effectively permanent resource and so the conversion of solar radiation into chemical or electrical energy is an attractive, although challenging, prospect. Photo‐electrochemical (PEC) water splitting is a key aspect of producing hydrogen from solar power. However, practical water oxidation over photoanodes (in combination with water reduction at a photocathode) in PEC cells is currently difficult to achieve because of the large overpotentials in the reaction kinetics and the inefficient photoactivity of the semiconductors. The development of semiconductors that allow high solar‐to‐hydrogen conversion efficiencies and the utilization of these materials in photoanodes will be a necessary aspect of achieving efficient, stable water oxidation. This Review discusses advances in water oxidation activity over photoanodes of n‐type visible‐light‐responsive (oxy)nitrides and oxides. 相似文献
159.
Simon D. Kloß Sophia Wandelt Andreas Weis Prof. Dr. Wolfgang Schnick 《Angewandte Chemie (International ed. in English)》2018,57(12):3192-3195
Advancing the attainable composition space of a compound class can lead to fascinating materials. The first tetravalent metal nitridophosphate, namely Hf9?xP24N52?4xO4x (x≈1.84), was prepared by high‐pressure metathesis. The Group 4 nitridophosphates are now an accessible class of compounds. The high‐pressure metathesis reaction using a multianvil setup yielded single crystals that were suitable for structure analysis. Magnetic properties of the compound indicate Hf in oxidation state +IV. Optical measurements show a band gap in the UV region. The presented route unlocks the new class of Group 4 nitridophosphates by significantly improving the understanding of this nitride chemistry. Hf9?xP24N52?4xO4x (x≈1.84) is a model system and its preparation is the first step towards a systematic exploration of the transition‐metal nitridophosphates. 相似文献
160.
Marta Falcone Lok Nga Poon Dr. Farzaneh Fadaei Tirani Prof. Marinella Mazzanti 《Angewandte Chemie (International ed. in English)》2018,57(14):3697-3700
Cleavage of dihydrogen is an important step in the industrial and enzymatic transformation of N2 into ammonia. The reversible cleavage of dihydrogen was achieved under mild conditions (room temperature and 1 atmosphere of H2) by the molecular uranium nitride complex, [Cs{U(OSi(OtBu)3)3}2(μ‐N)] 1, leading to a rare hydride–imide bridged diuranium(IV) complex, [Cs{U(OSi(OtBu)3)3}2(μ‐H)(μ‐NH)], 2 that slowly releases H2 under vacuum. This complex is highly reactive and quickly transfers hydride to acetonitrile and carbon dioxide at room temperature, affording the ketimide‐ and formate‐bridged UIV species [Cs{U(OSi(OtBu)3)3}2(μ‐NH)(μ‐CH3CHN)], 3 and [Cs{U(OSi(OtBu)3)3}2(μ‐HCOO)(μ‐NHCOO)], 4 . 相似文献