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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuzubov A. A., Tikhonova L. V., Fedorov A. S.
Заглавие : Ab initio investigation of a new boron nitride allotrope
Коллективы : Russian Foundation for Basic Research [12-02-00640]
Место публикации : Phys. Status Solidi B. - 2014. - Vol. 251, Is. 6. - P.1282-1285. - ISSN 0370-1972, DOI 10.1002/pssb.201350389. - ISSN 1521-3951
Примечания : Cited References: 31. - We acknowledge support of the Russian Foundation for Basic Research through Grant No. 12-02-00640. Also, we thank the Institute of Computer Modeling (Siberian Division, Russian Academy of Sciences, Krasnoyarsk), the Joint Supercomputer Center of the Russian Academy of Sciences (Moscow), the computer cluster "Chebyshev" of the Moscow State University (Moscow), and the supercomputer of the Institute of Space and Information Technologies of the Siberian Federal University for providing an opportunity to use their computers for performing all calculations.
Предметные рубрики: AUGMENTED-WAVE METHOD
MOLECULAR-DYNAMICS
TRANSITION
METALS
Ключевые слова (''Своб.индексиров.''): boron nitride--computational materials science--density functional theory--elastic properties--superhard materials
Аннотация: A new allotropic superhard and superdense structure of sp3-bonded boron nitride (hP3-BN) is proposed. Geometric electronic, elastic, and optical properties of the structure are investigated by density functional theory generalized gradient approximation (DFT-GGA) calculations. It is shown that the structure is an insulator with a band gap of 5.06 eV; is density is 5.03% higher than that of cubic boron nitride (c-BN) and its bulk modulus is 2.25% higher than that of c BN. The calculated hP3-BN refractive index in the range 200-800 nm is significantly higher than the indexes of diamond and all known carbon allotropes, expect for the analogous carbon h-P3 structure, and it has a large optical dispersion. In the range above 800 nm the refractive index changes from 2.60 to 2.35. (C) WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Y., Mitskan V. A., Korovushkin M. M.
Заглавие : Anomalous superconductivity and superfluidity in repulsive fermion systems
Место публикации : Phys. Usp.: Turpion, 2015. - Vol. 58, Is. 8. - P.733-761. - ISSN 10637869 (ISSN), DOI 10.3367/UFNe.0185.201508a.0785
Примечания : Cited References: 369. - We are grateful to M A Baranov, A V Chubukov, D V Efremov, M V Feigel'man, V V Kabanov, K I Kugel', M S Marienko, N M Plakida, N V Prokorev, A Ya Tzalenchuk, and V V Val'kov for the fruitful discussions and constant attention to our work. The work was supported by the Russian Foundation for Basic Research (project nos. 14-02-00058 and 14-02-31237). M Yu K thanks the Program of Basic Research of the National Research University Higher School of Economics for support. The work of MM K was supported by grant of the President of the Russian Federation (SP-1361.2015.1) and the Dinasty Foundation
Предметные рубрики: HEXAGONAL BORON-NITRIDE
SCANNING-TUNNELING-MICROSCOPY
2-DIMENSIONAL HUBBARD-MODEL
HIGH-TC SUPERCONDUCTIVITY
ELECTRON-ENERGY SPECTRUM
P-WAVE SUPERCONDUCTIVITY
DOUBLE-LAYER GRAPHENE
2D KONDO-LATTICE
GROUND-STATE
TRANSITION-TEMPERATURE
Ключевые слова (''Своб.индексиров.''): anomalous superconductivity--kohn-luttinger mechanism--superfluidity--repulsive fermi gas--hubbard and t-jmodel--shubin vonsovsky model--graphene monolayer--graphene bilayer
Аннотация: We discuss the mechanisms of unconventional superconductivity and superfluidity in 3D and 2D fermionic systems with purely repulsive interaction at low densities. We construct phase diagrams of these systems and find the areas of the superconducting state in free space, as well as on the lattice in the framework of the Fermi-gas model with hard-core repulsion, the Hubbard model, the Shubin-Vonsovsky model, and the t-J model. We demonstrate that the critical superconducting temperature can be greatly increased in the spin-polarized case or in a two-band situation already at low densities. The proposed theory is based on the Kohn-Luttinger mechanism or its generalizations and explains or predicts anomalous p-, d-, and f-wave pairing in various materials, such as high-temperature superconductors, the idealized monolayer and bilayer of doped graphene, heavy-fermion systems, layered organic superconductors, superfluid 3He, spin-polarized 3He mixtures in 4He, ultracold quantum gases in magnetic traps, and optical lattices.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Avramov P. V., Kuzubov A. A., Sakai S., Ohtomo M., Entani S., Matsumoto Y., Eleseeva N. S., Pomogaev V. A., Naramoto H.
Заглавие : Atomic structure and physical properties of fused porphyrin nanoclusters
Коллективы : JAEA Research fellowship; Russian Scientific Foundation [14-13-00139]
Место публикации : J. Porphyr. Phthalocyanines: World Scientific Publishing, 2014. - Vol. 18, Is. 7. - P.552-568. - ISSN 1088-4246, DOI 10.1142/S1088424614500291. - ISSN 1099-1409
Примечания : Cited References: 66. - This work was supported by JAEA Research fellowship (P. V. A.). P. V. A. also acknowledges JAEA ASRC and Molecular Spintronics Group for hospitality and fruitful collaboration. This work was supported by the Russian Scientific Foundation, Project No. 14-13-00139. Authors are grateful for Prof. S. G. Ovchinnikov for fruitful discussions.
Предметные рубрики: AUGMENTED-WAVE METHOD
HOLONOMIC QUANTUM COMPUTATION
INITIO MOLECULAR-DYNAMICS
VAPOR ABSORPTION SPECTRA
BORON-NITRIDE NANOTUBES
ELECTRONIC-STRUCTURE
REDOX REACTIONS
EXCITED-STATES
SPIN-STATES
GRAPHENE
Ключевые слова (''Своб.индексиров.''): nanoclusters--fused porphyrins--electronic structure--mechanical properties
Аннотация: The atomic and electronic structures, mechanical properties and potential barriers of formation of a set of meso–meso β–β fused porphyrin/metalloporphyrin nanopages, nanotapes, nanotubes and 2D nanofabrics were studied by GGA LC-DFT technique using cluster and PBC models. The porphyrin pages of the nanoclusters are connected with each other by graphene fragments formed by meso–meso β–β links. Fusion of all the edges of six porphyrin/metalloporphyrin units produces a novel ~ 1 nm sized molecule of cubic symmetry with a hollow cage inside. It was found that all studied nanoclusters are metastable with formation energies 0.36–7.57 kcal/mol per atom. Under applied mechanical stress, the nanoclusters exhibit superelastic and ultrastrong properties with binding graphene fragments being the weakest links for mechanical rupture. Depending on the spin-dependent reaction pathways, the hollow caged nanoclusters exhibit almost zero or low potential energy barriers (1–10 kcal/mol) during the initial stages of self-assembly. All nanoclusters exibit the main features of the electronic structures of the parent porphyrins, in particular the nature of HOMO/LUMO states and the relative energetic positions of the metal d states. The induced curvature of the hollow cage nanoclusters leads to admixture of more than 2% of the dπ⊥ states to the dσ energy region and formation of vacant superatomic molecular orbitals of d character in cubic ligand field. The Fe-derived hollow-caged nanoclusters reveal extremely high spin states with small energy differences between ferromagnetic and antiferromagnetic configurations, which can be utilized for quantum holonomic computations.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kablov E. N., Piskorskii V. P., Valeev R. A., Ospennikova O. G., Rezchikova I. I., Volkov N. V., Shaikhutdinov K. A.
Заглавие : Boron mobility in sintered (Pr, Dy)–(Fe, Co)–B materials with a high cobalt content
Место публикации : Russ. Metall. (Metally): Pleiades Publishing, 2014. - Vol. 2014, Is. 9. - P.721–724. - ISSN 0036-0295, DOI 10.1134/S0036029514090080. - ISSN 1555-6255
Примечания : Cited References: 15
Аннотация: Sintered (Pr, Dy)–(Fe1 – yCoy)–B materials with up to y ≈ 0.5 atomic fractions have been studied. Boron is found to be a movable element, and its diffusion between principal magnetic phase A and other boron containing phases determines the properties of the materials. The structure of principal magnetic phase grains is sufficiently complex: their periphery is enriched in boron. The enrichment is shown to cause a decrease in the coercive force of the materials to zero after sintering.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuzubov A. A., Kovaleva E. A., Avramov P. V., Kuklin A. V., Mikhaleva N. S., Tomilin F. N., Sakai S., Entani S., Matsumoto Y., Naramoto H.
Заглавие : Contact-induced spin polarization in BNNT(CNT)/TM (TM=Co, Ni) nanocomposites
Коллективы : Russian Scientific Fund [14-13-00139]
Место публикации : J. Appl. Phys.: American Institute of Physics, 2014. - Vol. 116, Is. 8. - Ст.084309. - ISSN 0021-8979, DOI 10.1063/1.4894157. - ISSN 1089-7550
Примечания : Cited References: 21. - This work was supported by the Russian Scientific Fund, Project No. 14-13-00139. The authors would like to thank Institute of Computational Modelling of SB RAS, Krasnoyarsk; Joint Supercomputer Center of RAS, Moscow; the HPC Research Department and Center of Equipment for Joint Use of Siberian Federal University, Krasnoyarsk; Siberian Supercomputer Center (SSCC) of SB RAS, Novosibirsk; and Laboratory of Parallel Information Technologies 21 of Research Computing Center of Moscow State University (the SKIF MSU "Chebyshev" system) for providing the access to their supercomputers.
Предметные рубрики: TOTAL-ENERGY CALCULATIONS
HEXAGONAL BORON-NITRIDE
WAVE BASIS-SET
AB-INITIO
PSEUDOPOTENTIALS
DISPERSION
NANOTUBE
NI(111)
Аннотация: The interaction between carbon and BN nanotubes (NT) and transition metal Co and Ni supports was studied using electronic structure calculations. Several configurations of interfaces were considered, and the most stable ones were used for electronic structure analysis. All NT/Co interfaces were found to be more energetically favorable than NT/Ni, and conductive carbon nanotubes demonstrate slightly stronger bonding than semiconducting ones. The presence of contact-induced spin polarization was established for all nanocomposites. It was found that the contact-induced polarization of BNNT leads to the appearance of local conductivity in the vicinity of the interface while the rest of the nanotube lattice remains to be insulating. (c) 2014 AIP Publishing LLC.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Avramov P. V., Kuzubov A. A., Sakai, Seiji, Ohtomo, Manabu, Entani, Shiro, Matsumoto, Yoshihiro, Naramoto, Hiroshi, Eleseeva N. S.
Заглавие : Contact-induced spin polarization in graphene/h-BN/Ni nanocomposites
Место публикации : J. Appl. Phys.: American Institute of Physics, 2012. - Vol. 112, Is. 11. - Ст.114303. - P. - ISSN 0021-8979, DOI 10.1063/1.4767134
Примечания : Cited References: 47. - This work was supported by JAEA Research fellowship (P.V.A.). P.V.A. also acknowledges JAEA ASRC and Molecular Spintronics Group for hospitality and fruitful collaboration. The authors are grateful to the ICS SB RAS and SFU CC (Krasnoyarsk), ISC RAS and MSU CRC, (SKIF MSU "Chebyshev", Moscow) for computer resources. This work was partially supported by the RFBR grant 12-02-31417.
Предметные рубрики: HEXAGONAL BORON-NITRIDE
TRILAYER GRAPHENE
NI(111) SURFACE
GRAPHITE
APPROXIMATION
SPINTRONICS
DIFFRACTION
SIMULATION
SUBSTRATE
CARBON
Аннотация: Atomic and electronic structure of graphene/Ni(111), h-BN/Ni(111) and graphene/h-BN/Ni(111) nanocomposites with different numbers of graphene and h-BN layers and in different mutual arrangements of graphene/Ni and h-BN/Ni at the interfaces was studied using LDA/PBC/PW technique. Using the same technique corresponding graphene, h-BN and graphene/h-BN structures without the Ni plate were calculated for the sake of comparison. It was suggested that C-top:C-fcc and N-top:B-fcc configurations are energetically favorable for the graphene/Ni and h-BN/Ni interfaces, respectively. The Ni plate was found to induce a significant degree of spin polarization in graphene and h-BN through exchange interactions of the electronic states located on different fragments. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4767134]
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ohtomo M., Yamauchi Y., Kuzubov A. A., Eliseeva N. S., Avramov P. V., Entani S., Matsumoto Y., Naramoto H., Sakai S.
Заглавие : Contact-induced spin polarization of monolayer hexagonal boron nitride on Ni(111)
Место публикации : Appl. Phys. Lett.: American Institute of Physics, 2014. - Vol. 104, Is. 5. - Ст.51604. - ISSN 0003-6951, DOI 10.1063/1.4863324. - ISSN 1077-3118
Примечания : Cited References: 20. - This study was supported by the Grant-in-Aid for Scientific Research (Grant Nos. 23860067 and 24760033) from the Japan Society for the Promotion of Science.
Предметные рубрики: METASTABLE DEEXCITATION SPECTROSCOPY
METAL-SURFACES
FILMS
TRANSITION
Аннотация: Hexagonal boron nitride (h-BN) is a promising barrier material for graphene spintronics. In this Letter, spin-polarized metastable de-excitation spectroscopy (SPMDS) is employed to study the spin-dependent electronic structure of monolayer h-BN/Ni(111). The extreme surface sensitivity of SPMDS enables us to elucidate a partial filling of the in-gap states of h-BN without any superposition of Ni 3d signals. The in-gap states are shown to have a considerable spin polarization parallel to the majority spin of Ni. The positive spin polarization is attributed to the pi-d hybridization and the effective spin transfer to the nitrogen atoms at the h-BN/Ni(111) interface. (C) 2014 AIP Publishing LLC.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Moshkina E. M., Seryotkin Y., Bovina A. F., Molokeev M. S., Eremin E. V., Belskaya N., Bezmaternykh L. N.
Заглавие : Crystal formation of Cu-Mn-containing oxides and oxyborates in bismuth-boron fluxes diluted by MoO3 and Na2CO3
Место публикации : J. Cryst. Growth. - 2018. - Vol. 503. - P.1-8. - ISSN 00220248 (ISSN), DOI 10.1016/j.jcrysgro.2018.09.011
Примечания : Cited References: 26. - This study was supported by Russian Foundation for Basic Research (RFBR) according to the research project No. 17-02-00953 A.
Ключевые слова (''Своб.индексиров.''): characterization--growth from solutions--single crystal growth--manganites--magnetic materials
Аннотация: The high-temperature crystallizing phases of fluxes (molten solutions) based on Bi2O3:MoO3 = 1:3 and diluted by Na2CO3 and B2O3 (under varying of Na2CO3:B2O3), and by CuO and Mn2O3 (0 ≤ Mn2O3:CuO ≤ 5) are studied. The conditions of the stable crystallization of Mn2+1−xCuxMoO4, Mn23+O3, Mn2+Mn23+O4, Mn2+1−xCuxMn3+BO4 and Mn2+2−xCuxMn3+BO5 have been found. The influence of MoO3 and Na2CO3 to the crystallization processes of Mn2+- and Mn3+-containing Mn2+1−xCuxMoO4 and Mn2+Mn23+O4 and Mn23+O3 are clarified. The occurrence of the chemical bonds of these types at the crystallization of Mn-heterovalent Mn2+1−xCuxMn3+BO4 and Mn2+2−xCuxMn3+BO5 oxyborates is studied. Single crystal growth techniques of these oxyborates are suggested. The results of the structural and magnetic characterization of some discussed compounds are presented.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Anistratov A. T., Vorobev A. V., Grekhov Y. N., Malyshevskii N. G.
Заглавие : Dark conductivity and photoconductivity of germanium-sillenite crystals doped with aluminum and boron
Место публикации : Fiz. Tverd. Tela. - 1980. - Vol. 22, Is. 6. - P.1865-1867. - ISSN 0367-3294
Примечания : Cited References: 6
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kulbakov A. A., Sarkar R., Janson O., Dengre S., Weinhold T., Moshkina E. M., Portnichenko P. Y., Luetkens H., Yokaichiya F., Sukhanov A. S., Eremina R. M., Schlender P., Schneidewind A., Klauss H. -H., Inosov D. S.
Заглавие : Destruction of long-range magnetic order in an external magnetic field and the associated spin dynamics in Cu2GaBO5 and Cu2AlBO5 ludwigites
Место публикации : Phys. Rev. B. - 2021. - Vol. 103, Is. 2. - Ст.024447. - ISSN 24699950 (ISSN), DOI 10.1103/PhysRevB.103.024447
Примечания : Cited References: 46. - We thank U. Nitzsche for technical assistance. This project was funded in part by the German Research Foundation (DFG) under Grant IN 209/9-1, via Project C03 of the Collaborative Research Center SFB 1143 (project-id 247310070) at the TU Dresden, and the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter—ct.qmat (EXC 2147, project-id 390858490). O.J. was supported by the Leibniz Association through the Leibniz Competition
Аннотация: The quantum spin systems Cu2M′BO5 (M′=Al,Ga) with the ludwigite crystal structure consist of a structurally ordered Cu2+ sublattice in the form of three-leg ladders, interpenetrated by a structurally disordered sublattice with a statistically random site occupation by magnetic Cu2+ and nonmagnetic Ga3+ or Al3+ ions. A microscopic analysis based on density-functional-theory calculations for Cu2GaBO5 reveals a frustrated quasi-two-dimensional spin model featuring five inequivalent antiferromagnetic exchanges. A broad low-temperature 11B nuclear magnetic resonance points to a considerable spin disorder in the system. In zero magnetic field, antiferromagnetic order sets in below TN≈4.1 K and ∼2.4 K for the Ga and Al compounds, respectively. From neutron diffraction, we find that the magnetic propagation vector in Cu2GaBO5 is commensurate and lies on the Brillouin-zone boundary in the (H0L) plane, qm=(0.45,0,−0.7), corresponding to a complex noncollinear long-range ordered structure with a large magnetic unit cell. Muon spin relaxation is monotonic, consisting of a fast static component typical for complex noncollinear spin systems and a slow dynamic component originating from the relaxation on low-energy spin fluctuations. Gapless spin dynamics in the form of a diffuse quasielastic peak is also evidenced by inelastic neutron scattering. Most remarkably, application of a magnetic field above 1 T destroys the static long-range order, which is manifested in the gradual broadening of the magnetic Bragg peaks. We argue that such a crossover from a magnetically long-range ordered state to a spin-glass regime may result from orphan spins on the structurally disordered magnetic sublattice, which are polarized in magnetic field and thus act as a tuning knob for field-controlled magnetic disorder.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fedorov A. S., Popov Z. I., Fedorov D. A., Eliseeva N. S., Serjantova M. V., Kuzubov A. A.
Заглавие : DFT investigation of the influence of ordered vacancies on elastic and magnetic properties of graphene and graphene-like SiC and BN structures
Место публикации : Phys. Status Solidi B. - 2012. - Vol. 249, Is. 12. - P.2549-2552. - ISSN 0370-1972, DOI 10.1002/pssb.201200105
Примечания : Cited References: 32. - The work was supported by The Ministry of education and science of Russia, project 14.B37.21.0163. The authors express their gratitude to the Joint Supercomputer Center, Russian Academy of Sciences, Moscow and the supercomputer center of the Moscow State University (SKIF-MGU) for the possibility of using their computer clusters to perform all calculations.
Предметные рубрики: WALLED CARBON NANOTUBES
INITIO MOLECULAR-DYNAMICS
AB-INITIO
DEFECTS
STATE
MONOLAYER
POINTS
Ключевые слова (''Своб.индексиров.''): boron nitride--carbon silicide--elastic properties--graphene--magnetic properties--vacancies
Аннотация: Influence of ordered monovacancies on elastic properties of graphene is theoretically investigated by density functional theory (DFT) calculations. Inverse linear dependence of the graphene Young's modulus on the concentration of vacancies has been revealed and migration rate of the vacancies has been calculated as a function of applied strain. It is shown that the migration rate can be controlled by applying various strains or temperatures. The influence of ordered monovacancies on magnetic properties of graphene as well as graphene-like hexagonal carbon silicide (2D-SiC) and the boron nitride (h-BN) structures is investigated. It is established that the presence of vacancies in all systems yields the appearance of local magnetic moment. However, in 2D-SiC structure the magnetic moment occurs only in the case of a Si vacancy. Influence of the distance between vacancies on the ferromagnetic or anti-ferromagnetic ordering for all structures is established. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazak N. V., Gavriliuk A. G., Ovchinnikov S. G., Lyubutin I. S., Edel'man I. S., Rudenko V. V.
Заглавие : Evolution of the optical absorption spectra and electronic structure of the VBO3 crystal under high pressures
Коллективы : Russian Foundation for Basic Research [07-02-00490a, 08-02-00897a, 08-02-90708 mob_st, 09-02-00171a, 07-02-00226]; Federal Agency for Science and Innovation [MK-4278.2008.2, 01.164.12.HB11]; Russian Academy of Sciences
Место публикации : J. Exp. Theor. Phys. - 2009. - Vol. 109, Is. 3. - P.455-465. - ISSN 1063-7761, DOI 10.1134/S1063776109090118
Примечания : Cited References: 27. - We would like to thank A. D. Vasil'ev for performing the X-ray diffraction investigations.This study was supported by the Russian Foundation for Basic Research (project nos. 07-02-00490a, 08-02-00897a, 08-02-90708 mob_st, 09-02-00171a, and 07-02-00226), the Federal Agency for Science and Innovation (Rosnauka) (project no. MK-4278.2008.2, contract no. 01.164.12.HB11), and the Branch of Physical Sciences of the Russian Academy of Sciences within the framework of the program "Strongly Correlated Electrons."
Предметные рубрики: BAND-STRUCTURE
PHASE-TRANSITION
FEBO3
FE1-XVXBO3
STATE
MODEL
Ключевые слова (''Своб.индексиров.''): charge-transfer excitations--d-d transitions--ferromagnetic semiconductor--fundamental absorption edge--high pressure--optical absorption spectrum--absorption--boron--boron compounds--electronic properties--electronic structure--optical materials--oxygen--vanadium--light absorption
Аннотация: The evolution of optical absorption spectra of the ferromagnetic semiconductor VBO3 under high pressures up to 70 GPa has been investigated. It has been revealed that, below the fundamental absorption edge (E (g1) = 3.02 eV), the spectra exhibit a series of bands V1 (2.87 eV), V2 (2.45 eV), V3 (1.72 eV), and V4(1.21 eV) due to the d-d transitions in the V3+ ion and charge-transfer excitations. A model of the electronic structure of the VBO3 semiconductor has been constructed. This model combines the one-electron description of the s and p states of boron and oxygen and the many-electron description of the vanadium d states.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sorokin P. B., Avramov P.V., Yakobson B.I., Chernozatonskii L.A.
Заглавие : Magnesium Boride Nanotubes: Relative Stability and Atomic and Electronic Structure
Место публикации : J. Phys. Chem. C. - 2010. - Vol. 114, Is. 11. - P.4852-4856. - MAR 25. - ISSN 1932-7447, DOI 10.1021/jp9112014
Примечания : Cited Reference Count: 38. - Гранты: P.B.S. and B.I.Y. acknowledge support by the Basic Energy Sciences division of the Department of Energy, award DE-SC0001479. L.A.C. was supported by the Russian Academy of Sciences, program No. 21. P.V.A ad P.B.S. also acknowledge the collaborative RFBR-JSPS grant No. 09-02-92107-R Phi. We are grateful to the Joint Supercomputer Center of the Russian Academy of Sciences for the possibility of using a cluster computer for quantum chemical calculations. The geometry of all presented structures was visualized by commercial ChemCraft software (http://www.chemcraftprog.com).Финансирующая организация: Basic Energy Sciences division of the Department of Energy [DE-SC0001479]; Russian Academy of Sciences [21]; RFBR-JSPS [09-02-92107-RPhi]
Предметные рубрики: BORON
PSEUDOPOTENTIALS
FULLERENES
SIMULATION
FORM
Ключевые слова (''Своб.индексиров.''): basic composition--bending behavior--comparative studies--diborides--energy analysis--energy minima--magnesium atom--magnesium boride--mgb2--relative stabilities--semiconducting behavior--small-diameter--staggered configuration--sub-lattices--bending (forming)--borides--boron--electronic properties--electronic structure--energy management--magnesium--nanotubes--density functional theory
Аннотация: A comparative study of file energies and the electronic structure of MgBx nanotubes is performed within the framework of the density functional theory. Different basic compositions (x = 2 for diboride and x = 3 for triboride) and different diameters (3 angstrom D 18 angstrom), as well the exterior, interior, and staggered placement of magnesium atoms, are considered. Energy analysis reveals a nontrivial bending behavior of the MgB2 sheets. such that the tubes with exterior and staggered configurations display the energy minima at certain small diameters (of the boron cage sublattice). The semiconducting behavior of narrow MgB2 nanotubes with exterior Mg position was observed.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ganzhenko I. M., Yakubaylik E. K.
Заглавие : Magnetite losses decrease at the Abagurskaya concentrating plant
Место публикации : Obogashch. Rud. - 2015. - Is. 1. - P.22-25. - ISSN 0202-3776
Примечания : Cited References: 7
Ключевые слова (''Своб.индексиров.''): magnetite--magnetic separator--neodymium-iron-boron--magnetic-field intensity--saturation magnetization, residual and in different fields--coercive force--specific magnetic susceptibility
Аннотация: Presently, owing to the wet magnetic concentration technology and equipment improvement, losses of magnetite iron in tailings were reduced close to 1 % at all iron ore processing facilities. This raises the question of magnetite losses limit value that may be reached on the basis of the available engineering and technical provision. The results of the investigations, performed with a view to estimate achievable level of magnetite losses at the Abagurskaya concentrating plant, are presented. As a result of the composition and magnetic properties investigations, carried out on samples of concentrate and classifiers overflow products, as well as final tailings in all processing operations, it was established, that losses of magnetite iron in tailings could be reduced to 0.5 %. With that, decrease by 0.15 % may be achieved by means of replacement of all barium-ferrite systems with the ones made of neodymium-iron-boron alloy, and by 0.30 %-through application of separators of the type PBR-P-90/250A in magnetite heavy-medium regeneration, as well as application of neodymium-iron-boron alloy magnets.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Moshkina E. M., Krylov A. S., Kokh D., Shabanova K., Molokeev M. S., Bovina A. F., Plyaskin M., Rostovtsev N., Bezmaternykh L. N.
Заглавие : Multicomponent flux growth and composition control of Cu2MnBO5:Ga ludwigites
Место публикации : CrystEngComm. - 2022. - Vol. 24, Is. 19. - P.3565-3575. - ISSN 14668033 (ISSN), DOI 10.1039/d2ce00258b
Примечания : Cited References: 26. - This study was supported by the Russian Science Foundation (Grant No. 21-72-00130). The Raman, X-ray, and EDX data were obtained using the analytical equipment of the Krasnoyarsk Regional Center of Research Equipment of the Federal Research Center “Krasnoyarsk Science Center SB RAS”
Аннотация: To reach the concentration phase boundary between antiferromagnetic Cu2GaBO5 and ferrimagnetic Cu2MnBO5 ludwigites, solid solutions Cu2Mn1−xGaxBO5 (x = 0.05, 0.1, 0.15, 0.175) were grown by the flux technique using a multi-component solvent based on Bi2Mo3O12 with the addition of Na2B4O7 which significantly influenced the crystal formation and cation composition of the studied compounds. The content of the flux system was corrected taking into account the earlier established relationship of the partition coefficients of Mn2O3 and Ga2O3. The influence of the solvent components on the ludwigite crystallization was analyzed. The maximum size of the grown crystal was 1 × 1 × 4 mm3. The structure and cation composition of the grown compounds were studied using X-ray (X-ray diffraction, EDX (energy-dispersive X-ray spectroscopy)) and vibrational (Raman) spectroscopy techniques. The phase boundary of Cu2MnBO5–Cu2GaBO5 was found to be in the concentration range of x = 0.15–0.175, corresponding to a change in the monoclinic axis direction and a leap in the lattice parameters. The symmetry evolution of metal–oxygen octahedra for four nonequivalent cation positions was analyzed, and the unique crystal structure of Cu2MnBO5 demonstrated high rigidity relative to the introduction of Ga3+ cations. The polarized Raman spectra of monoclinic ludwigites were obtained and studied for the first time. A comparison of the spectra of the studied samples in both phases and orthorhombic ludwigites was made. A number of spectral features due to the monoclinic distortions in the crystal were found. In agreement with the Raman experiment, the concentration phase boundary was close to 0.15.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chernozatonskii L. A., Sorokin P. B., Yakobson B. I.
Заглавие : New boron barrelenes and tubulenes
Место публикации : JETP Letters. - 2008. - Vol. 87, Is. 9. - P.489-493. - ISSN 0021-3640, DOI 10.1134/S0021364008090087
Примечания : Cited References: 21
Предметные рубрики: MOLECULAR-DYNAMICS
NANOTUBES
TRANSITION
SIMULATION
Аннотация: The structure of a new class of boron nanostructures-barrelenes and tubulenes-based on a boron atomic lattice constructed by the alternating B-atomic polygons with central atoms and without them has been proposed and their properties have been described. Ab initio density functional calculations have been performed for the energy and electronic structure of the fullerene-barrelene-nanotube series based on the lowest energy fullerene B-80. It has been shown that the energy and band gap of a barrelene are lower than the respective quantities of the corresponding fullerene and tend to the respective values for nanotubes in the infinite limit. It has been shown that there are isomers of nanotubes of the same type that are significantly different in symmetry and electronic properties: a semiconductor (C-5v symmetry) and a metal (D-5h symmetry).
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Entani, Shiro, Larionov K. V., Popov Z. I., Takizawa, Masaru, Mizuguchi, Masaki, Watanabe, Hideo, Li, Songtian, Naramoto, Hiroshi, Sorokin, Pavel B., Sakai, Seiji
Заглавие : Non-chemical fluorination of hexagonal boron nitride by high-energy ion irradiation
Место публикации : Nanotechnology. - 2020. - Vol. 31, Is. 12. - Ст.125705. - ISSN 0957-4484, DOI 10.1088/1361-6528/ab5bcc. - ISSN 1361-6528 (eISSN)
Примечания : Cited References: 53
Аннотация: Two-dimensional materials such as hexagonal boron nitride (h-BN) and graphene have attracted wide attention in nanoelectronics and spintronics. Since their electronic characteristics are strongly affected by the local atomic structure, the heteroatom doping could allows us to tailor the electronic and physical properties of two-dimensional materials. In this study, a non-chemical method of heteroatom doping into h-BN under high-energy ion irradiation was demonstrated for the LiF/h-BN/Cu heterostructure. Spectroscopic analysis of chemical states on the relevant atoms revealed that 6 ± 2% fluorinated h-BN are obtained by the irradiation of 2.4 MeV Cu2+ ions with the fluence up to 1014 ions/cm2. It was shown that the high-energy ion irradiation leads to a single-sided fluorination of h-BN by the formation of the fluorinated sp 3-hybridized BN.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lyubutin I. S., Gavriliuk A. G., Andryushin N. D., Pavlovskiy M. S., Zinenko V. I., Lyubutina M. V., Troyan I. A., Smirnova E. S.
Заглавие : Pressure-Induced Structural Transition to the Polar Phase in GdFe3(BO3)4
Место публикации : Cryst. Growth Des. - 2019. - Vol. 19, Is. 12. - P.6935-6944. - ISSN 15287483 (ISSN), DOI 10.1021/acs.cgd.9b00609
Примечания : Cited References: 39. - The authors express their deep gratitude to Prof. S. G. Ovchinnikov for initiating this work and fruitful discussions. These studies were performed with the support of the Ministry of Science and Higher Education within the State assignment FSRC "Crystallography and Photonics" RAS in part for the synchrotron Mössbauer measurements. Support from RFBR Grant No. 17-02-00766 in part for the Raman spectroscopy measurements and from No. 18-02-00696 in part for the theoretical calculations is also acknowledged. For preparation and tests of high-pressure cells, (39) the facilities of Center for Collective Use “Accelerator Center for Neutron Research of the Structure of Substance and Nuclear Medicine” of the INR RAS were used.
Аннотация: The GdFe3(BO3)4 crystal has attracted great interest as a magnetic-field-induced multiferroic. In this paper, we show that the multiferroic properties in this crystal can be induced by high pressure. At high pressures up to 50 GPa, created in diamond anvil cells, the structural and vibrational (phonon) properties of the GdFe3(BO3)4 crystal were studied. The structural phase transition was detected at about 23–25 GPa by Raman and synchrotron Mössbauer (NFS) spectroscopy. First-principle calculations of the crystal lattice dynamics at pressures below and above the structural transition were carried out. It was established that at pressures above the structural transition, the space group R32 of GdFe3(BO3)4 is changed to the polar space group R3, and the crystal becomes a ferroelectric. At the R32 → R3 transition, the displacement of the boron ion B(2) and oxygen O results in the formation of boron–oxygen B(2)O4 tetrahedrons instead of the plane BO3 triangles. Meanwhile, the triangle oxygen environment of boron in the site B(1) remains unchanged. The nearest environment of the gadolinium ion also changes significantly. Instead of six oxygen ions in the R32 phase, the nearest surroundings of Gd in the R3 phase consist of nine oxygen ions forming a complex polyhedron. A large hysteresis of the transition indicates that this crystal remains a ferroelectric with a decrease in pressure to about ambient pressure.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sobol A. A., Shukshin V. E., Zaitsev A. I.
Заглавие : Raman spectroscopy of crystalline, glassy, and molten states of lead diborate
Место публикации : Opt. Spectrosc: Maik Nauka-Interperiodica Publishing, 2016. - Vol. 121, Is. 6. - P.810-818. - ISSN 0030400X (ISSN), DOI 10.1134/S0030400X16120249
Примечания : Cited References: 30. - This work was performed with financial support from RFBR, research project no. 13-02-00707.
Ключевые слова (''Своб.индексиров.''): boron--crystalline materials--raman scattering--single crystals--internal vibration--molten state--oxygen complexes--phonon lines--polarized raman spectra--glass
Аннотация: Polarized Raman spectra of single crystals of lead diborate, PbB4O7 (PBO), are studied in detail at 300 K. The TO-, LO-, and IO-phonon lines of the A1, A2, B1, and B2 symmetries in the Raman spectra of this compound are assigned. Changes in the Raman spectra of the internal vibrations of boron–oxygen complexes upon transition from the crystalline to the glassy and the molten states of PBO are observed. On the basis of the obtained results, the regularities in the formation of boron–oxygen complexes in glasses, melts, and crystals of the PbO · 2B2O3, SrO · 2B2O3, and Li2O · 2B2O3. diborate compositions are analyzed. © 2016, Pleiades Publishing, Ltd.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vasil'eva I. G., Dovlitova L. S., Zajkovskij V. I., Malakhov V. V., Edel'man I. S., Stepanov A. S., Aleksandrov K. S.
Заглавие : Real composition and structure of manganese ferrite nanoparticles dispersed in the K-Al-B-O glasses
Место публикации : Dokl. Akad. Nauk. - 2005. - Vol. 401, Is. 3. - P.349-352. - ISSN 0869-5652
Ключевые слова (''Своб.индексиров.''): aluminum--boron compounds--ferrite--manganese--nanostructured materials--particles (particulate matter)--structure (composition)--borate glasses--exchange interaction--glass
Аннотация: For the first time the problem of determining real composition and structure of manganese ferrite nanoparticles dispersed borate glasses is solved using differentiating dissolution and high-resolution X-ray electron microscopy techniques. For the first time the nanosize effect of aluminum incorporation in manganese ferrite composition is experimentally shown, thus directly confirming the hypothesis of Al participation in exchange interaction between paramagnetic Fe and Mn ions as diamagnetic diluter.
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