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141.
Falk Meutzner Dr. Matthias Zschornak Dr. Artem A. Kabanov Tina Nestler Dr. Tilmann Leisegang Prof. Vladislav A. Blatov Prof. Dirk C. Meyer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(36):8623-8629
We have created a set of crystalline model structures exhibiting straight lines of Al3+ connected to chalcogenides (O2−, S2−, and Se2−) connected to metal cations of varying valence (Sr2+, Y3+, Zr4+, Nb5+, and Mo6+). They were relaxed with density functional theory computations and analysed by Bader partitioning. As Al3+ ions are supposed to strongly interact with their atomic environment, we studied the electron density topology induced by higher-valent cations in the extended chemical neighbourhood of Al. In fact, we found a general decrease of ionic charges and an increasing displacement of the chalcogenides towards higher-valent ions for the heavier chalcogens. Therefore, we comprehensively screened S- and Se-containing compounds for candidates theoretically exhibiting low migration barriers for Al3+ ions by using Voronoi–Dirichlet partitioning and bond valence site energy calculations. The basis for this search is the Inorganic Crystal Structure Database. Indeed, we could extract six promising candidates with low Al3+ migration barriers. which are even lower than the barriers for any other element inside of these materials. This will encourage efforts towards preparing suitable Al3+ conductors. 相似文献
142.
We consider semidefinite programs (SDPs) with equality constraints. The variable to be optimized is a positive semidefinite matrix X of size n. Following the Burer-Monteiro approach, we optimize a factor Y of size n × p instead, such that X = YYT. This ensures positive semidefiniteness at no cost and can reduce the dimension of the problem if p is small, but results in a nonconvex optimization problem with a quadratic cost function and quadratic equality constraints in Y. In this paper, we show that if the set of constraints on Y regularly defines a smooth manifold, then, despite nonconvexity, first- and second-order necessary optimality conditions are also sufficient, provided p is large enough. For smaller values of p, we show a similar result holds for almost all (linear) cost functions. Under those conditions, a global optimum Y maps to a global optimum X = YYT of the SDP. We deduce old and new consequences for SDP relaxations of the generalized eigenvector problem, the trust-region subproblem, and quadratic optimization over several spheres, as well as for the Max-Cut and Orthogonal-Cut SDPs, which are common relaxations in stochastic block modeling and synchronization of rotations. © 2019 Wiley Periodicals, Inc. 相似文献
143.
Todorov Vladislav T. Dutsov Chavdar Ch. Cassette Philippe Mitev Krasimir K. 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(8):3249-3258
Journal of Radioanalytical and Nuclear Chemistry - This work shows a study of the effect of the non-uniformity of photocathode response on the energy resolution of plastic scintillators optimized... 相似文献
144.
Alexander V. Gorbunov Vladimir A. Kuznetsov Andrey S. Zhuravlev Leonid V. Kulik Sergey Dickmann Vladislav B. Timofeev 《Annalen der Physik》2019,531(6)
Experimental results on the properties of a recently discovered new collective state, the magnetofermionic condensate, are summarized herein. Condensation occurs in a fermionic system, a quantum Hall insulator (filling factor ν = 2), as a result of the formation of a dense ensemble of long‐lived spin cyclotron magnetoexcitons, composite bosons. At temperatures below 1 K, the exciton ensemble exhibits a sharp enhancement in its response to an external electromagnetic field due to the formation of a super‐absorbing state that interacts coherently with the electromagnetic field. Simultaneously, the electrons below the Fermi level rearrange to form a new non‐equilibrium radiative recombination channel. The condensate shows a sharp decrease in viscosity and the ability to spread over macroscopically large distances, on the order of a millimeter, at a speed of . Due to this rapid long‐distance spin transfer, new opportunities in the field of spintronics have been opened up. 相似文献
145.
Jonas Köhling Dr. Volodymyr Kozel Dr. Vladislav Jovanov Dr. Romana Pajkert Dr. Sergey N. Tverdomed Oleg Gridenco Malte Fugel Prof. Dr. Simon Grabowsky Prof. Dr. Gerd-Volker Röschenthaler Prof. Dr. Veit Wagner 《Chemphyschem》2019,20(5):665-671
A blue-light emitting material based on a boron complex containing heteroaromatic phosphonate ligand is synthesized and characterized. The Phospho-Fries rearrangement is used in the synthesis route of the ligand as a convenient method of introducing phosphonate groups into phenols. Structural, thermal and photophysical properties of the resulting oxazaborinin phosphonate compound have been characterized. DFT geometry optimizations were studied as well as the spatial position and symmetry of the HOMO and LUMO. Good thermal stability up to 250 °C enables vacuum deposition methods next to solution processing. Combining the work function with the optical band gap from UV-Vis measurements shows that band alignment is possible with standard contact materials. Photoluminescence reveals an emission peak at 428 nm, which is suitable for a blue light-emitter. 相似文献
146.
Barkovskii Savelii V. Ulitko Maria V. Barkov Alexey Yu. Kochnev Ivan А. Zimnitskiy Nikolay S. Korotaev Vladislav Yu. Sosnovskikh Vyacheslav Ya. Stepanyuk Roman А. Madzhidov Timur I. 《Chemistry of Heterocyclic Compounds》2022,58(8-9):462-472
Chemistry of Heterocyclic Compounds - A method for a regio- and stereoselective synthesis of N-unsubstituted... 相似文献
147.
148.
Vladislav Y. Korotaev Vyacheslav Y. Sosnovskikh Alexey Y. Barkov Pavel A. Slepukhin Yurii V. Shklyaev 《Journal of heterocyclic chemistry》2012,49(4):856-860
Uncatalyzed cycloaddition of 3,4‐dihydroisoquinolines to (E)‐1,1,1‐trifluoro‐3‐nitro‐2‐butene via Grob reaction provide a simple one‐step route to the 5,6‐dihydropyrrolo[2,1‐a]isoquinolines, which represent the basic structural framework of the antitumor active alkaloid crispine. 相似文献
149.
150.