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21.
Zaleski-Ejgierd P Labet V Strobel TA Hoffmann R Ashcroft NW 《J Phys Condens Matter》2012,24(15):155701
An initial observation of the formation of WH under pressure from W gaskets surrounding hydrogen in diamond anvil cells led to a theoretical study of tungsten hydride phases. At P = 1 atm no stoichiometry is found to be stable with respect to separation into the elements, but as the pressure is raised WH(n) (n = 1-6, 8) stoichiometries are metastable or stable. WH and WH(4) are calculated to be stable at P > 15 GPa, WH(2) becomes stable at P > 100 GPa and WH(6) at P > 150 GPa. In agreement with experiment, the structure computed for WH is anti-NiAs. WH(2) shares with WH a hexagonal arrangement of tungsten atoms, with hydrogen atoms occupying octahedral and tetrahedral holes. For WH(4) the W atoms are in a distorted fcc arrangement. As the number of hydrogens rises, the coordination of W by H increases correspondingly, leading to a twelve-coordinated W in WH(6). In WH(8) H(2) units also develop. All of the hydrides considered should be metallic at high pressure, though the Fermi levels of WH(4) and WH(6) lie in a deep pseudogap. Prodded by these theoretical studies, experiments were then undertaken to seek phases other than WH, exploring a variety of experimental conditions that would favor further reaction. Though a better preparation and characterization of WH resulted, no higher hydrides have as yet been found. 相似文献
22.
Piet Schönherr Shilei Zhang Yuanqian Liu Patryk Kusch Stephanie Reich Terence Giles Dominik Daisenberger Dharmalingam Prabhakaran Yulin Chen Thorsten Hesjedal 《固体物理学:研究快报》2015,9(2):130-135
A novel topological insulator with orthorhombic crystal structure is demonstrated. It is characterized by quasi one‐dimensional, conducting atomic chains instead of the layered, two‐dimensional sheets known from the established Bi2(Se,Te)3 system. The Sb‐doped Bi2Se3 nanowires are grown in a TiO2‐catalyzed process by chemical vapor deposition. The binary Bi2Se3 is transformed from rhombohedral to orthorhombic by substituting Sb on ~38% of the Bi sites. Pure Sb2Se3 is a topologically trivial band insulator with an orthorhombic crystal structure at ambient conditions, and it is known to transform into a topological insulator at high pressure. Angle‐resolved photoemission spectroscopy shows a topological surface state, while Sb doping also tunes the Fermi level to reside in the bandgap. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
23.
Patryk Pagacz 《Linear algebra and its applications》2012,436(9):3065-3071
24.
Journal of Theoretical Probability - A sum of a large-dimensional random matrix polynomial and a fixed low-rank matrix polynomial is considered. The main assumption is that the resolvent of the... 相似文献
25.
Comparative, fully relativistic (FR), scalar relativistic (SR) and non-relativistic (NR) DFT calculations attribute about 30% of the mercury-battery voltage to relativity. The obtained percentage is smaller than for the lead-acid battery, but not negligible. 相似文献
26.
We investigated multi-phonon processes in two types of CdSe nanocrystals, spherical quantum dots and nanorods by temperature-dependent Raman spectroscopy. We find the anharmonic constants relating to the two- and three-phonon decay channels to systematically change with changing nanocrystal size. The contributions from two-phonon processes decrease with decreasing diameter, while the contributions from higher-order processes increase. The anharmonicities in the vibrational potential increase due to the phonon confinement, and we did not find a shape dependence. 相似文献
27.
The computation of the reliability function of a (complex) coherent system is a difficult task. Hence, sometimes, we should simply work with some bounds (approximations). The computation of these bounds has been widely studied in the case of coherent systems with independent and identically distributed (IID) components. However, few results have been obtained in the case of heterogeneous (non ID) components. In this paper, we derive explicit bounds for systems with heterogeneous (independent or dependent) components. Also some stochastic comparisons are obtained. Some illustrative examples are included where we compare the different bounds proposed in the paper. 相似文献
28.
Patryk Przygocki Paula Ratajczak Franois Bguin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(50):18137-18145
Enhancing the operating voltage of supercapacitors (SCs), hence their specific energy, is important. However, long‐term hold at high voltage entails loss of capacitance, increase of resistance and internal pressure. Such detrimental effects could be reduced by obtaining quantitative information on the relative impact of the various mechanisms leading to the worsening of the SCs performance. Now, for a carbon/carbon supercapacitor in aqueous Li2SO4, a self‐consistent approach is used to assign leaking charge during high voltage hold to the charge: 1) distributed throughout the electrochemical cell (steady‐state leakage current measurements), 2) spent at each electrode for gases production (operando electrochemical mass spectrometry (EMS) analysis and pressure records), 3) utilized to oxidize the electrodes surface (from post‐mortem surface functionality determination by temperature programmed desorption (TPD)), and 4) used for other parasitic reactions. 相似文献
29.
Pyykkö P Hakala MO Zaleski-Ejgierd P 《Physical chemistry chemical physics : PCCP》2007,9(23):3025-3030
A family of infinite nanostrips is computationally predicted. In it monomers of single, double or triple aromatic rings are linked to each other by strong C-Au-C, C-Au <-- N or N --> Au <-- N bonds. Depending on the geometry of the system and saturation of the bonds, these 1-D nanostrips are found to be insulators, narrow- or zero-gap semiconductors, or metals. The calculated dimerization and polymerization energies suggest clear exothermicity of formation. Varying the nitrogen content in the aromatic ring is found to little affect the geometry, and the 1-D band structure of the strips can be interpreted in a rigid-band picture. The orbital character of the states at the Fermi level has been analyzed. One of the new structures is found to be closely similar to graphene with respect to its band structure properties. 相似文献
30.
Krzysztof Ryo Katarzyna Jdruchniewicz Patrycja Krasucka Wojciech Biszczak Patryk Oleszczuk 《Molecules (Basel, Switzerland)》2022,27(22)
The properties of biochar (BC) from crustacean chitin are relatively well understood, while there are few studies on BC from insect chitin. This study presents the characterization and phytotoxic assessment of BC produced from crickets and cricket chitin. Cricket powder (BCCR) and cricket chitin (BCCH) were pyrolyzed at 500 °C and 700 °C. Physicochemical characteristics, N ad-/desorption, FTIR, were examined. SEM images were also performed. Regardless of the pyrolysis temperature, biochars were characterized by a densely “packed” solid surface/monolithic type with a non-porous structure (0.05–0.22 m2/g) and high content of N (9.4–11.8%). BCCHs showed a higher pH (12.2–12.4) compared to BCCR (8.7–10.8). Based on the XRD analysis, BCs were characterized by an amorphous carbon turbostratic structure and a randomly oriented graphitic-like micro-crystallite structure. FTIR spectra of BCs confirmed the presence of various O2 and N-functional groups on the BC surface. BCCHs added to soil at rates from 0.5 to 1.5% significantly reduced the germination of Lepidium sativum. Stimulation of root elongation was also observed in the case of BCCR500 1.0% and BCCR700 1.5%. Thermal degradation of cricket powder and cricket chitin promotes the formation of organic N-containing heterocyclic rings, which lead to the production of N-doped carbons with potential uses in energy storage and the contaminations sorption. 相似文献