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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Nikiforov A. A., Krylov A. S., Krylova S. N., Gorshkov V. S., Pelegov D. V.
Заглавие : Temperature Raman study of Li4Ti5O12 and ambiguity in the number of its bands
Колич.характеристики :10 с
Место публикации : J. Raman Spectrosc. - 2024. - Vol. 55, Is. 3. - P.406-415. - ISSN 03770486 (ISSN), DOI 10.1002/jrs.6641. - ISSN 10974555 (eISSN)
Примечания : Cited References: 51. - The research was funded by the Russian Science Foundation (project No 22-22-00350, https://rscf.ru/project/22-22-00350)
Аннотация: The two primary physical methods for identifying lithium titanate, a negative electrode material used commercially, are X-Ray diffraction and Raman spectroscopy. Although there are many publications on this topic, they are focused mainly on chemistry, so there are still some points that require clarification from a physical and methodological point of view. Difference of experimentally observed and theoretically predicted Raman spectra was explained through a combination of experiments and computations. The work comprises experiments and computations to explain why there are different numbers of predicted and observed Raman-active bands. Our low-temperature study and the analysis of thermal shifts during heating led us to conclude that the approach with surplus bands is advantageous and we recommend using major F2g band shifts to estimate the sample heating.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Krylova S. N., Vtyurin A. N., Roginskii, Evgenii M., Jin, Li, Tian, Ye, Wei, Xiaoyong
Заглавие : Temperature phase transitions in silver niobate and lithium-tantal-modified silver niobate ceramics
Место публикации : Phys. Chem. Chem. Phys. - 2023. - Vol. 25, Is. 16. - P.11410-11417. - ISSN 14639076 (ISSN), DOI 10.1039/D3CP00607G. - ISSN 14639084 (eISSN)
Примечания : Cited References: 42. - The work was financially supported by the Russian Foundation for Basic Research and DFG project number No 21-52-12018. The temperature Raman experiments were performed in the Krasnoyarsk Regional Center of Research Equipment of Federal Research Center “Krasnoyarsk Science Center SB RAS”
Аннотация: The temperature behaviour of the 0.955 AgNbO3--0.045 LiTaO3and AgNbO3 ceramics were studied in the range from 10 to 415 K by Raman spectroscopy. Ab initio calculations of the Raman spectra in the Pmc21 phase of AgNbO3 were carried out using three potentials (A-PZ, PBE, PBEsol) for spectra interpretation. The Raman spectra peculiarities in AgNbO3 ceramics is observed and explained. The differences in the spectra of the 0.955 AgNbO3--0.045 LiTaO3 and AgNbO3 ceramics are shown. The temperatures of structural changes in the 0.955 AgNbO3--0.45 LiTaO3 and AgNbO3 ceramics were discussed. The structural phase transition below 120 K have been observed in silver niobate. The phase transition has been observed at 310 K and below 150 K in 0.955 AgNbO3--0.045 LiTaO3.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Isaenko L., Dong L., Kurus A., Lin Z., Yelisseyev A., Lobanov S., Molokeev M. S., Korzhneva K., Goloshumova A.
Заглавие : LixAg1–xGaSe2: interplay between lithium and silver in mid-infrared nonlinear optical chalcogenides
Место публикации : Adv. Opt. Mater. - 2022. - Vol. 10, Is. 24. - Ст.2201727. - ISSN 21951071 (ISSN), DOI 10.1002/adom.202201727
Примечания : Cited References: 37. - This work was supported by the National Natural Science Foundation of China (Grant No. 22133004), Russian Science Foundation, grant # 19‐12‐00085‐P (crystal growth, crystal structure analysis, band gap measurement) and partly done on state assignment of IGM SB RAS (composition chemical analysis)
Аннотация: AgGaSe2 and LiGaSe2 are two famous mid-infrared nonlinear optical (NLO) materials with similar chemical formula but different structural symmetry. The former material has relatively larger NLO effect and birefringence but rather small energy band gap, while the latter is the opposite. Aiming at achieving a good balance of NLO properties, here the substitution between silver and lithium ions on the evolution of structural and optical properties in a new series of LixAg1–xGaSe2 crystals is systematically investigated. It reveals that, with the increase of Li content, LixAg1–xGaSe2 almost keeps the same tetragonal symmetry with AgGaSe2 until x ≈ 0.9. The NLO effects and birefringence values vary with respect to x with the largest variation at x = 0.8–0.9. The optimal combination of birefringence (0.03–0.025) and nonlinear parameters (26–30 pm V−1) is achieved at x = 0.4–0.5. As the energy band gap increases with the increase of x, the maximal value of 2.2 eV for chalcopyrite structure suggests that the laser-induced damage threshold of LixAg1–xGaSe2 would be as large as five-fold of AgGaSe2. This study provides a good example to show that the rational substitution between Li and Ag can significantly improve the balance of NLO properties in chalcogenides.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kurus, Alexey, Yelisseyev, Alexander, Lobanov, Sergei, Plyusnin, Pavel, Molokeev M. S., Solovyev, Leonid, Samoshkin, Dmitry, Stankus, Sergei, Melnikova S. V., Isaenko, Lyudmila
Заглавие : Thermophysical properties of lithium thiogallate that are important for optical applications
Коллективы : Russian Science Foundation, RussiaRussian Science Foundation (RSF) [19-12-00085]; RFBRRussian Foundation for Basic Research (RFBR) [20-42-543006\20]; Novosibirsk region [20-42-543006\20]
Место публикации : RSC Adv. - 2021. - Vol. 11, Is. 62. - P.39177-39187. - ISSN 2046-2069(eISSN), DOI 10.1039/d1ra05698k
Примечания : Cited References: 41. - Crystal growth and investigation of physical properties were supported by Russian Science Foundation, Russia (#19-12-00085). Spectroscopic study was performed on a state assignment of the Institute of Geology and Mineralogy, Siberian Branch of Russian Academy of Sciences Russia and Ministry of Science and Higher Education, Russia. Measurements of thermal conductivity were funded by RFBR and Novosibirsk region (grant #20-42-543006\20)
Предметные рубрики: NON-ENANTIOMORPHOUS CRYSTAL
MID-IR
SINGLE-CRYSTALS
FLASH METHOD
Аннотация: Lithium thiogallate LiGaS2 is one of the most common nonlinear crystals for mid-IR due to its extreme beam strength and wide transparency range; however, its thermophysical properties have not yet been practically studied. Large crystals of high optical quality are grown. DTA revealed features at 1224 K below melting point (1304 K) that are associated with the oxygen containing compounds of the LiGaO2−xSx type. The thermal conductivity of LiGaS2 (about 10.05 W (m−1 K−1)) and band gap value (3.93 eV at 300 K) are found to be the highest in the LiBC2 family. Isotropic points in the dispersion characteristics for the refractive index are found and LiGaS2-based narrow-band optical filters, smoothly tunable with temperature changes, are demonstrated. Intense blue photoluminescence of anionic vacancies VS is observed at room temperature after annealing LiGaS2 in vacuum, whereas orange low-temperature emission is related to self-trapped excitons. When LiGaS2 crystals are heated, spontaneous luminescence (pyroluminescence) takes place, or thermoluminescence after preliminary UV excitation; the parameters of traps of charge carriers are estimated. The obtained data confirm the high optical stability of this material and open up prospects for the creation of new optical devices based on LiGaS2.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Drokina T. V., Petrakovskii G. A., Bayukov O. A., Molokeev M. S., Vorotynov A. M., Popkov S. I., Velikanov D. A.
Заглавие : Physical properties of a frustrated uasi-one-dimensional NaCuFe2(VO4)3 magnet and effect of chemical pressure induced by the substitution of sodium for lithium
Место публикации : Phys. Solid State. - 2020. - Vol. 62, Is. 2. - P.297-307. - ISSN 10637834 (ISSN), DOI 10.1134/S1063783420020122
Примечания : Cited References: 22
Аннотация: The structural, thermal, static magnetic, and resonance properties of the low-dimensional NaCuFe2(VO4)3 compound obtained by the solid-phase synthesis have been investigated. In the temperature range of 110–300 K, the electron spin resonance in the X band with a g factor of 2.008 has been detected. The magnetic properties of a sample with a high frustration level in the paramagnetic, antiferromagnetic, and disordered states have been examined. A shift of the Neel temperature to the high-temperature region in an external magnetic field has been observed. The origin of the disordered magnetism in NaCuFe2(VO4)3 are discussed. The features of substitution of sodium for lithium on the physical properties of the ACuFe2(VO4)3 (A = Na, Li) system have been established. It is shown that the chemical pressure changes the crystal lattice parameters, spacings between magnetic ions, and crystallite size, which is reflected in the physical properties of the material.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chen M., Xia Z., Molokeev M. S., Wang T., Liu Q.
Заглавие : Tuning of photoluminescence and local structures of substituted cations in xSr2Ca(PO4)2-(1 - x)Ca10Li(PO4)7:Eu2+ phosphors
Место публикации : Chem. Mater.: American Chemical Society, 2017. - Vol. 29, Is. 3. - P.1430-1438. - ISSN 08974756 (ISSN), DOI 10.1021/acs.chemmater.7b00006
Примечания : Cited References: 37. - The present work was supported by the National Natural Science Foundation of China (Grants 91622125 and 51572023), Natural Science Foundations of Beijing (2172036), and Fundamental Research Funds for the Central Universities (FRF-TP-15-003A2).
Ключевые слова (''Своб.индексиров.''): calcium--energy transfer--europium--light emission--lithium--luminescence--phosphors--photoionization--photoluminescence--single crystals--composition ranges--crystal-field splitting--luminescence measurements--non-linear variation--photoionization process--polyhedra distortion--rare earth doped solids--temperature dependent--solid solutions
Аннотация: Local structure modification in solid solution is an essential part of photoluminescence tuning of rare earth doped solid state phosphors. Herein we report a new solid solution phosphor of Eu2+-doped xSr2Ca(PO4)2-(1 - x)Ca10Li(PO4)7 (0 ≤ x ≤ 1), which share the same β-Ca3(PO4)2 type structure in the full composition range. Depending on the x parameter variation in xSr2Ca(PO4)2-(1 - x)Ca10Li(PO4)7:Eu2+, the vacancies generated in the M(4) site enable the nonlinear variation of cell parameters and volume, and this increases the magnitude of M(4)O6 polyhedra distortion. The local structure modulation around the Eu2+ ions causes different luminescent behaviors of the two-peak emission and induces the photoluminescence tuning. The shift of the emission peaks in the solid solution phosphors with different compositions has been discussed. It remains invariable at x ≤ 0.5, but the red-shift is observed at x 0.5 which is attributed to combined effect of the crystal field splitting, Stokes shift, and energy transfer between Eu2+ ions. The temperature-dependent luminescence measurements are also performed, and it is shown that the photoionization process is responsible for the quenching effect.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Golovnev N. N., Molokeev M. S., Lesnikov M. K., Vereshchagin S. N.
Заглавие : Polymeric lithium(I) diaquabarbiturate: Crystal structure
Коллективы : Ministry of Education and Science of the Russian Federation [3049]
Место публикации : Russ. J. Inorg. Chem.: MAIK Nauka-Interperiodica / Springer, 2017. - Vol. 62, Is. 6. - P.746-750. - ISSN 0036-0236, DOI 10.1134/S0036023617060092. - ISSN 1531-8613(eISSN)
Примечания : Cited References:23. - This work was performed in the Siberian Federal University within the State task of the Ministry of Education and Science of the Russian Federation for the period of 2014-2016 (project no. 3049).
Предметные рубрики: IONIC CO-CRYSTALS
BARBITURIC-ACID
COMPLEXES
NA
LI
Аннотация: The lithium(I) catena-diaquabarbiturate complex [Li(H2O)2(HBA–O,O′)]n (I), where Н2ВА is barbituric acid, has been structurally characterized by X-ray diffraction (CIF file CCDC no. 1447689), and its thermal decomposition and IR spectrum have been studied. Crystals of complex I are monoclinic, a = 6.4306(7) Å, b = 16.720(1) Å, c = 7.1732(8) Å, β = 108.253(4)°, V = 732.5(1) Å3, space group P21/c, and Z = 4. One independent μ2-bridging HBA– ligand is coordinated to two Li(I) ions via the two oxygen atoms of C4(6)=O carbonyl groups. Each Li+ ion is linked with two μ2-HBA– ions and two terminal water molecules at tetrahedron vertices. μ2-HBA– ions link tetrahedra into a chain. The structure is stabilized by multiple hydrogen bonds and π–π-interaction between HBA–. The shift of ν(C=O) vibration bands in the IR spectrum of complex I in comparison with Н2ВА towards lower frequencies agrees with the coordination of HBA– via oxygen atoms. The dehydration of complex I occurs in two stages in the regions of 100–150 and 150–240°C.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chen M., Xia Z., Molokeev M. S., Lin C. C., Su C., Chuang Y. -C., Liu Q.
Заглавие : Probing Eu2+ luminescence from different crystallographic sites in Ca10M(PO4)7:Eu2+ (M = Li, Na, and K) with β-Ca3(PO4)2-type structure
Место публикации : Chem. Mater.: American Chemical Society, 2017. - Vol. 29, Is. 17. - P.7563-7570. - ISSN 08974756 (ISSN), DOI 10.1021/acs.chemmater.7b02724
Примечания : Cited References: 34. - The present work was supported by the National Natural Science Foundation of China (Grants 51722202, 91622125, and 51572023), Natural Science Foundations of Beijing (2172036), and Fundamental Research Funds for the Central Universities (FRF-TP-16-002A3). C.C.L. and C.C.S. acknowledge the financial support from the Ministry of Science and Technology of Taiwan (Contract No. MOST 104-2113-M-027-007-MY3), and M. Molokeev acknowledges support of the Russian Foundation for Basic Research (17-52-53031).
Ключевые слова (''Своб.индексиров.''): calcium--doping (additives)--excited states--light emission--lithium--luminescence--phosphors--photoluminescence--positive ions--rietveld refinement--single crystals--color tuning--crystallographic sites--different distributions--emission bands--local environments--long wavelength bands--luminescent centers--power diffraction data--europium
Аннотация: Eu2+ local environments in various crystallographic sites enable the different distributions of the emission and excitation energies and then realize the photoluminescence tuning of the Eu2+ doped solid state phosphors. Herein we report the Eu2+-doped Ca10M(PO4)7 (M = Li, Na, and K) phosphors with β-Ca3(PO4)2-type structure, in which there are five cation crystallographic sites, and the phosphors show a color tuning from bluish-violet to blue and yellow with the variation of M ions. The difference in decay rate monitored at selected wavelengths is related to multiple luminescent centers in Ca10M(PO4)7:Eu2+, and the occupied rates of Eu2+ in Ca(1), Ca(2), Ca(3), Na(4), and Ca(5) sites from Rietveld refinements using synchrotron power diffraction data confirm that Eu2+ enters into four cation sites except for Ca(5). Since the average bond lengths d(Ca-O) remain invariable in the Ca10M(PO4)7:Eu2+, the drastic changes of bond lengths d(M-O) and Eu2+ emission depending on the variation from Li to Na and K can provide insight into the distribution of Eu2+ ions. It is found that the emission band at 410 nm is ascribed to the occupation of Eu2+ in the Ca(1), Ca(2), and Ca(3) sites with similar local environments, while the long-wavelength band (466 or 511 nm) is attributed to Eu2+ at the M(4) site (M = Na and K). We show that the crystal-site engineering approach discussed herein can be applied to probe the luminescence of the dopants and provide a new method for photoluminescence tuning.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Bondarev V. S., Raevskaya S. I., Flerov I. N., Malitskaya M. A., Raevskii I. P.
Заглавие : Thermophysical study of structural phase transitions in Na0.95Li0.05NbO3 solid solution
Место публикации : Bull. Russ. Acad. Sci. Phys.: Allerton Press, 2016. - Vol. 80, Is. 9. - P.1046-1050. - ISSN 10628738 (ISSN), DOI 10.3103/S1062873816090148
Примечания : Cited References: 18. - This work was supported by Southern Federal University, project no. 213.01-2014/012-VG.
Ключевые слова (''Своб.индексиров.''): niobium oxide--sodium--specific heat--temperature distribution--thermal expansion--ceramic samples--effect of heat treatments--possible mechanisms--sodium lithium niobate--structural distortions--structural phase transition--temperature dependence--temperature range--lithium
Аннотация: Temperature dependences of specific heat Cp(T) and coefficient of thermal expansion α(T) for Na0.95Li0.05NbO3 sodium-lithium niobate ceramic samples are investigated in the temperature range of 100–800 K. The Cp(T) and α(T) anomalies at T3 = 310 ± 3 K, T2 = 630 ± 8 K, and T1 = 710 ± 10 K are observed, which correspond to the sequence of phase transitions N ↔ Q ↔ S(R) ↔ T2(S). The effect of heat treatment of the samples on the sequence of structural distortions was established. It is demonstrated that annealing of the samples at 603 K leads to splitting of the anomaly corresponding to the phase transition Q → R/S in two anomalies. After sample heating to 800 K, the only anomaly is observed in both the Cp(T) and α(T) dependence. Possible mechanisms of the observed phenomena are discussed.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Михалева Н. С., Кузубов, Александр Александрович, Попов, Захар Иванович, Еремина А. Д., Высотин, Максим Александрович
Заглавие : Теоретическое исследование внедрения атомов лития в кремний
Место публикации : Вестник СибГАУ. - Красноярск: СибГАУ, 2015. - Т. 16, № 2. - С. 456-463. - ISSN 1816-9724
Примечания : Библиогр.: 55
Ключевые слова (''Своб.индексиров.''): диффузия--литий--кремний--dft--diffusion--lithium--silicon
Аннотация: Рассматривается процесс диффузии атомов лития в приповерхностные слои кремния (001). Расчеты выполнялись в рамках теории функционала плотности. Показано, что при малой концентрации лития на реконструированной поверхности кремния (001) энергия связи в подповерхностном слое ниже, чем на поверхности, что препятствует диффузии лития внутрь кристалла. Подобная ситуация существенно не меняется при увеличении температуры. Анализ частот перескока одиночных атомов лития с поверхности в приповерхностные слои показал, что в случае малых концентраций миграция атомарного Li будет осуществляться практически по одному пути реакции (из положения L-состояния, в котором литий находится в канале между димерами). При концентрации лития в два монослоя, наоборот, диффузия в подповерхностные слои становится более предпочтительна. Поскольку при достижении концентрации в один монослой происходит изменение симметрии димеров, диффузия лития внутрь кристалла также облегчается вследствие увеличения плотности положений в каналах между димерами. Таким образом, результат моделирования позволил объяснить причину экспериментального факта затруднения диффузии лития при прохождении через данную поверхность и определить пути возможной модификации поверхности, которая должна увеличить энергию связи атомов лития в приповерхностных состояниях при низких степенях заполнения им поверхности.The article deals with a theoretical investigation of lithium diffusion through silicon (001) surface within density functional theory formalism. It was shown that it is more energetically favorable for dilute lithium atoms to stay atop fully-relaxed silicon (001) surface than beneath it. This fact hampers the diffusion into the silicon crystal and the situation doesn't change significantly with increase in temperature. The frequencies of lithium atom hopping from the surface to the subsurface layers of silicon crystal were estimated. The analysis of frequencies for different transition paths indicates that in the case of dilute concentration Li atoms are likely to migrate through the surface from one type of sites (site L-located in channels between silicon dimers). With increasing of lithium concentration up to 1 monolayer and further, the silicon (001) surface swaps the asymmetric dimers reconstruction model for symmetric, leading to doubling of number of the sites in between silicon dimers. After the concentration reaches 2 monolayers, the binding energy of Li atoms on the surface becomes less than binding energy beneath the surface, so the diffusion turns to be thermodynamically allowed. As a result of the investigation, the ab-initio modeling puts light on the cause of experimentally observed decelerated lithium diffusion through silicon (001) surface and delivers an opportunity to determine possible techniques for surface modification, which will increase lithium atom binding energies in sites beneath silicon surface at low lithium concentrations.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vyunishev A. M., Sheremet’eva Y. A., Nasedkin B. A., Baturin I. S., Akhmatkhanov A. R., Shur V. Y.
Заглавие : Second harmonic generation of femtosecond laser pulses under Raman-Nath nonlinear diffraction
Место публикации : Bull. Russ. Acad. Sci. Phys.: Allerton Press, 2015. - Vol. 79, Is. 2. - P.190-193. - ISSN 1062-8738, DOI 10.3103/S106287381502032X
Примечания : Cited References: 8. - This work was supported by the Grant of the President of the Russian Federation MK-250.2013.2; by RFBR Grant No 15-02-03838; Krasnoyarsk Regional Fund for Science and Technical Activity Support; and by the Russian Academy of Sciences, Project no. 24.31. A.R. Akhmatkhanov is grateful for the support given to young scientists under the Developmental Program of the Ural Federal University.
Ключевые слова (''Своб.индексиров.''): diffraction--harmonic analysis--laser pulses--nonlinear optics--pulse generators--ultrafast lasers--ultrashort pulses--angular characteristics--cherenkov--lithium niobate--nonlinear diffraction--periodic domain structures--theoretical modeling--harmonic generation
Аннотация: The second harmonic generation of femtosecond laser pulses under Raman-Nath nonlinear diffraction in periodic domain structures of lithium niobate is considered. A theoretical model of Cherenkov nonlinear diffraction is used to calculate the spectral-angular characteristics of the second harmonic generation of femtosecond laser pulses under Raman-Nath nonlinear diffraction. Reliability of the results is confirmed by the experimental data. © 2015, Allerton Press, Inc.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pachauri, Neha, Khodadadi B., Althammer M., Singh A.V., Loukya B., Datta R., Iliev M., Bezmaternykh L. N., Gudim I. A., Mewes T., Gupta A.
Заглавие : Study of structural and ferromagnetic resonance properties of spinel lithium ferrite (LiFe5O8) single crystals
Коллективы : NSF [ECCS-1102263], NSF-CAREER [0952929], ICMS
Место публикации : J. Appl. Phys.: American Institute of Physics, 2015. - Vol. 117, Is. 23. - Ст.233907. - ISSN 0021, DOI 10.1063/1.4922778. - ISSN 10897550(eISSN)
Примечания : Cited References:32. - This work has been supported by NSF Grant No. ECCS-1102263. Tim Mewes and Behrouz Khodadadi would like to acknowledge support by the NSF-CAREER Award No. 0952929. R. Datta and B. Loukya sincerely acknowledge ICMS for providing advanced microscopy facility and funding. We thank Sahar Keshavarz, Archana Panikar, Stefan Kingler, and Jamileh Beik Mohammadi for help with the experimental work.
Предметные рубрики: EFFECTIVE LINEWIDTH
MAGNETIC-PROPERTIES
FIELD
TEMPERATURE
DEPENDENCE
Аннотация: The effect of B-site cation ordering on the room temperature structural and ferromagnetic resonance (FMR) properties of single crystal spinel lithium ferrite (LiFe5O8, LFO) have been investigated. A detailed microstructural analysis is done through X-ray diffraction, polarized Raman spectroscopy, and transmission electron microscopy (TEM) to examine the effect of post-annealing on the B-site cation ordering. The X-ray diffraction pattern of the as-grown crystal indicates a disordered state of the crystal. However, the annealed sample shows additional superlattice reflections corresponding to the ordered phase. This ordering is further confirmed by Raman spectra and TEM images, which reveal ordering of Li and Fe ions at the octahedral sites contrasting with the relatively high degree of octahedral site disorder in the as-grown crystal. To study the effect of B-site ordering on the magnetic properties and FMR linewidth, vibrating sample magnetometry and broadband FMR measurements have been performed for both the ordered and disordered phases of lithium ferrite. The value of saturation magnetization for both phases is ∼290 emu/cm3. A single mode FMR profile is observed for both phases with little distortion. The linewidth characteristics of the ordered and disordered phases of lithium ferrite phases are compared, and it is observed that the linewidth is independent of the cation ordering. Both the phases exhibit a low linewidth (∼26 Oe at 30 GHz) and the effective damping parameter for the as-grown and annealed samples is determined to be 0.0021 ± 0.0001.Влияние катионного упорядочения в Б-позициях при комнатной температуре на структурные свойства и ферромагнитный резонанс (ФМР) монокристалла литий железной шпинели (LiFe5O8, LFO) были исследованы. Подробный анализ микроструктуры делается с использованием рентгеновской дифракции, спектроскопии комбинационного рассеяния поляризованного света и просвечивающей электронной микроскопии (ПЭМ), чтобы изучить влияние после отжига на катионное упорядочение в B-позиции. Рентгеновская дифракционная картина, так выращенных кристаллов указывает на беспорядочное состояние кристалла. Тем не менее, пример показывает дополнительные индексы, соответствующие сверхрешетчатой упорядоченной фазы, при отжиге. Этот порядок подтверждается также спектрами комбинационного рассеяния и ТЕМ изображений, которые показывают порядок ионов Li и Fe в октаэдрических контрастными с относительно высокой степенью восьмигранной расстройства позиций в выращенных кристаллах. Для изучения влияния упорядочения В-позиций на магнитные свойства и ширины линии ФМР, вибрационные образцы магнитометрии и широкополосных ФМР измерений были выполнены как для упорядоченных и неупорядоченных фаз литиевого феррита. Значение намагниченности насыщения для обоих фаз ~290 emu / см3. Одиночный профиль в режиме ФМР наблюдается для обеих фаз с небольшим искажением. Ширина линии характеристики упорядоченной и неупорядоченной фаз литиевых ферритов сравниваются, и следует отметить, что ширина линии не зависит от катионного упорядочения. Оба фазы проявляют малую ширину линии (Э около 26 на 30 ГГц) и эффективный параметр демпфирования, как, для только выращенных, так и для отожженных образцов, определяется как 0,0021 ± 0,0001.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mikhaleva N. S., Visotin M. A., Popov Z. I., Kuzubov A. A., Fedorov A. S.
Заглавие : Ab initio and empirical modeling of lithium atoms penetration into silicon
Место публикации : Comput. Mater. Sci.: Elsevier, 2015. - Vol. 109. - P.76-83. - ISSN 0927-0256, DOI 10.1016/j.commatsci.2015.06.024
Примечания : Cited References: 69. - The authors would like to thank the Institute of Computational Modeling SB RAS, Krasnoyarsk, Information Technology Centre Novosibirsk State University, for providing access to their computational resources. The reported study was supported by RFBR, research project No. 14-02-31071, 14-02-31309, 12-02-00640, by the Council of the President of the Russian Federation for Support of Young Scientists and Leading Scientific Schools (project No. NSh-2886.2014.2), Increase Competitiveness Program of NUST "MISiS" (No. K2-2015-033). The authors also would like to thank Prof. Stephan Irle and L.R. Moskvina for fruitful discussions and helpful ideas.
Предметные рубрики: LONG CYCLE LIFE
CORE-LEVEL SPECTROSCOPY
CARBON-COATED SILICON
AUGMENTED-WAVE METHOD
ION BATTERIES
MOLECULAR-DYNAMICS
INTERATOMIC POTENTIALS
ELECTRONIC-STRUCTURE
CRYSTALLINE SILICON
SI(100)2X1 SURFACE
Ключевые слова (''Своб.индексиров.''): li-ion batteries--silicon--surface diffusion--li diffusion--density functional theory--molecular dynamics
Аннотация: A process of lithium atoms penetration into silicon (1 0 0) subsurface layers was investigated with the help of DFT method. It was shown that, while the concentration of lithium adatoms on reconstructed (1 0 0) silicon surface is low, the bonding energy of lithium atoms in the subsurface layers is smaller than the bonding energy on the surface, so lithium atoms are unlikely to migrate into the crystal. When the (1 0 0) silicon surface is covered by 2 layers of lithium, migration into the subsurface layer becomes favorable. In addition to this, the reconstruction of the surface changes to the form with symmetric dimers as the concentration increases. Thus, all possible lithium migration paths become energy-wise equal, so the rate of lithium atom transfer into silicon crystal rises. In addition to the ab initio calculations, an ad-hoc empirical interatomic potential was developed and the kinetics of lithium diffusion into silicon were studied. It was shown that lithium penetration proceeds in a layer-by-layer way with a sharp border between undoped and lithiated silicon. This is accounted for the fact that, once a tetrahedral interstice is occupied by a lithium atom, the migration barriers between the adjacent interstices become lower and the rate of diffusion increases. © 2015 Elsevier B.V. All rights reserved.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vyunishev A. M., Arkhipkin V. G., Chirkin, A. S.
Заглавие : Theory of second-harmonic generation in a chirped 2D nonlinear optical superlattice under nonlinear Raman-Nath diffraction
Коллективы : Council of the President of the Russian Federation [MK-2908.2015.2]; Russian Foundation for Basic Research (RFBR) [15-02-03838]
Место публикации : J. Opt. Soc. Am. B: Optical Society of America, 2015. - Vol. 32, Is. 12. - P.2411-2416. - ISSN 0740-3224, DOI 10.1364/JOSAB.32.002411. - ISSN 1520-8540(eISSN)
Примечания : Cited References:31. - Council of the President of the Russian Federation (MK-2908.2015.2); Russian Foundation for Basic Research (RFBR) (15-02-03838).
Предметные рубрики: FEMTOSECOND LASER-PULSES
POLED LITHIUM-NIOBATE
PHOTONIC CRYSTAL
COMPRESSION
CONVERSION
Аннотация: We analyze second-harmonic generation (SHG) in a two-dimensional nonlinear optical superlattice (NLOS) with its modulation period being chirped in the propagation direction and constant in the transverse direction. This results in efficient multiple SHG via nonlinear Raman–Nath diffraction. We obtain exact analytical expressions for a SH amplitude generated in chirped 2D NLOSs and for its quasi-phase-matching bandwidth. The results of analytical calculations are in excellent agreement with the numerical ones. We show that the process is robust to angular deviations of NLOS and it can be applied to enable tunable and broadband frequency conversion.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Кузубов, Александр Александрович, Михалева Н. С., Попов, Захар Иванович, Краснов, Павел Олегович, Николаева К. М.
Заглавие : Теоретическое исследование влияния допирования поверхности Si (100) на сорбцию и диффузию лития
Место публикации : Вестник СибГАУ. - Красноярск, 2015. - Т. 16, № 3. - С. 743-749. - ISSN 1816-9724
Примечания : Библиогр.: 56. - Исследование выполнено при финансовой поддержке РФФИ в рамках научных проектов No 14-02-31071, 14-02-31309. Авторы выражают благодарность информационно-вычислительному центру (ИВЦ) Новосибирского государственного университета (Новосибирск), Институту компьютерного моделирования СО РАН (Красноярск), Межведомственному суперкомпьютерному центру РАН (Москва), компьютерному центру СФУ, а также НИВЦ МГУ «Лаборатории параллельных информационных технологий» (система СКИФ МГУ «Ломоносов») за предоставление возможности использования вычислительных кластеров, на которых были проведены все расчеты.
Ключевые слова (''Своб.индексиров.''): диффузия--литий--кремний--кремний--допирование--метод функционала плотности (dft)--diffusion--lithium--silicon--doping--dft
Аннотация: В настоящее время перспективным анодным материалом нового поколения считается кремний, поскольку он имеет самую высокую теоретическую удельную емкость (4200 мАч/г). Однако одной из проблем, препятствующих широкому использованию данного материала, является медленная диффузия лития с поверхности кремния в объем, которая может быть решена с помощью модификации поверхности кремния. Проведено моделирование поверхностных процессов сорбции и диффузии лития в допированной поверхности Si (100) с помощью метода функционала плотности. В ходе исследования допирования Si (100) одиночными атомами B, Ga, Ge выявлено, что для всех выбранных нами допантов наиболее выгодны положения замещения кремния, а не адсорбции. Энергия связи допанта с пластиной кремния ослабевает в ряду от германия к галлию. Найдено, что атом бора замещает атом третьего слоя кремния, а германий и галлий занимают положение в первом слое. Тенденция первоначальной сорбции атомов лития в канале между димерами по сравнению с чистым материалом сохраняется и при допировании одиночными атомами B, Ga, Ge. Наблюдается значительное снижение (в случае бора) и увеличение (для галия и германия) энергетических барьеров перехода атома лития по поверхности кремниевой пластины. Величины энергетических барьеров перехода L-U с поверхности в приповерхностные слои при допировании возрастают на 0,05 эВ, что свидетельствует о замедлении данной стадии. В результате работы было обнаружено, что допирование бором, галлием и германием (концентрация составляет 0,3 атомных %) поверхности Si (100) не оказывает значительного влияния на сорбционные и диффузионные параметры.Currently, silicon is the most promising anode material for a new generation of lithium-ion batteries due to its very high theoretical specific capacity (4200 mAh/g). However, one of the problems hindering the wider use of this material is the slow diffusion of lithium from silicon surface into volume that can be solved by modifying silicon surface. The simulation of surface processes of sorption and diffusion of lithium in doped Si (100) was carried out by using the density functional method. In the study Si (100) doped with single atoms B, Ga, Ge, found that the silicon replacement compared to adsorption are more profitable for all dopants. The binding energy of dopant to silicon decreases from germanium to gallium. It was found that boron atom substitutes for the third layer of silicon, germanium and gallium occupy positions in the first layer. In comparison with the pure material the trend of initial lithium sorption in the channel between silicon dimmers retain for Si (100) doped with single atoms of B, Ga, Ge. Energy barriers of lithium transition on silicon surface substantially reduce (in the case of boron) and increase (in the case of gallium and germanium). The energy barrier of transition from surface to surface layers L-U during the doping increases by 0.05 eV, this shows a moderation of the stage. According to the study, Si (100) doping with boron, gallium and germanium (concentration of 0.3 atomic %) has not significant influence on sorption and diffusion parameters.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Smirnov M. B., Roginskii E. M., Kazimirov V. Y., Smirnov K. S., Baddour-Hadjean R., Pereira-Ramos J. P., Zhandun V. S.
Заглавие : Spectroscopic and computational study of structural changes in γ-LiV2O5 cathodic material induced by lithium intercalation
Место публикации : J. Phys. Chem. C: American Chemical Society, 2015. - Vol. 119, Is. 36. - P.20801-20809. - ISSN 1932-7447, DOI 10.1021/acs.jpcc.5b05540
Примечания : Cited References: 36. - This work was supported by the international collaboration program between the Centre National de la Recherche Scientifique (CNRS) of France and the Russian Foundation for Basic Research (RFBR), LIBASTRAM CNRS Project 6094, and RFBR Grant 13-03-91052.
Предметные рубрики: AUGMENTED-WAVE METHOD
LIXV2O5 SYSTEM
AB-INITIO
VANADIUM PENTOXIDE
RAMAN-SPECTROSCOPY
LI INTERCALATION
OXIDE
V2O5
TRANSITION
TRANSITION
Аннотация: Structure, electronic states, and vibrational dynamics of γ-LiV2O5 were studied by combined use of quantum-chemical calculations and Raman spectroscopy. The spin-polarized DFT+U calculations correctly mimic the structural changes induced by the Li intercalation into the V2O5 framework. The analysis of the density of electronic states shows that the electrons of Li atoms are transferred to the Vb atoms and are aligned in ferromagnetic order. The charge distribution in the system reflects the change of valence state of the Vb atoms from 5+ to 4+, and it is in line with changes of Vb–O bond lengths. The calculated Raman spectrum of the γ-LiV2O5 structure is in line with the experimental Raman spectra that allows a reliable assignment of all prominent Raman peaks. Comparison of the spectra of γ-LiV2O5 and γ'-V2O5 indicates spectral signatures of structural changes induced by the Li insertion into the γ'-V2O5 lattice. Results of the study present the opportunity of using Raman spectroscopy for characterization of structural modifications of the vanadate framework upon intercalation of guest species.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vyunishev A. M., Arkhipkin V. G., Slabko V. V., Baturin I. S., Akhmatkhanov A. R., Shur, V. Ya., Chirkin A. S.
Заглавие : Nonlinear Raman-Nath diffraction of femtosecond laser pulses in a 2D nonlinear photonic crystal
Коллективы : Council of the President of the Russian Federation [MK-2908.2015.2], Ministry of Education and Science of the Russian Federation [2014/7, UID RFMEFI59414X0011], Russian Foundation for Basic Research (RFBR) [13-02-01391-a, 14-02-01160-a, 15-02-03838]
Место публикации : Opt. Lett.: Optical Society of America, 2015. - Vol. 40, Is. 17. - P.4002-4005. - ISSN 0146, DOI 10.1364/OL.40.004002. - ISSN 15394794(eISSN)
Примечания : Cited References:27. - Council of the President of the Russian Federation (MK-2908.2015.2); Ministry of Education and Science of the Russian Federation (2014/7, UID RFMEFI59414X0011); Russian Foundation for Basic Research (RFBR) (13-02-01391-a, 14-02-01160-a, 15-02-03838).
Предметные рубрики: POLED LITHIUM-NIOBATE
2ND-HARMONIC GENERATION
BEAMS
Аннотация: We study second-harmonic generation (SHG) of femtosecond laser pulses in a rectangular two-dimensional nonlinear photonic crystal (NLPC). Multiple SH beams were observed in the vicinity of the propagation direction of the fundamental beam. It has been verified that the angular positions of these beams obey the conditions of nonlinear Raman-Nath diffraction (NRND). The measured SH spectra of specific NRND orders consist of narrow peaks that experience a high-frequency spectral shift as the order grows. We derive an analytical expression for the process studied and find the theoretical results to be in good agreement with the experimental data. We estimate the enhancement factor of nonlinear Raman-Nath diffraction in 2D NLPC to be 70. (C) 2015 Optical Society of America
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vyunishev A. M., Slabko V. V., Baturin I. S., Akhmatkhanov A. R., Shur V. Y.
Заглавие : Nonlinear Raman-Nath diffraction of femtosecond laser pulses
Коллективы : Russian Federation [MK-250.2013.2]; Krasnoyarsk Regional Fund for Science and Technical Activity Support; RAS grant [24.31]; Ural Federal University Development Program
Место публикации : Opt. Lett.: Optical Society of America, 2014. - Vol. 39, Is. 14. - P.4231-4234. - ISSN 0146-9592, DOI 10.1364/OL.39.004231. - ISSN 1539-4794
Примечания : Cited References: 22. - This work was partially supported by the Grant of the President of the Russian Federation MK-250.2013.2, Krasnoyarsk Regional Fund for Science and Technical Activity Support and by the RAS grant no. 24.31. A. A. acknowledges the financial support of young scientists through the Ural Federal University Development Program. The authors thank A. S. Chirkin and I. V. Timofeev for fruitful discussions and A. V. Barannik for optical microscopy of the samples.
Предметные рубрики: STRONTIUM BARIUM NIOBATE
2nd-HARMONIC GENERATION
PHOTONIC STRUCTURES
DOMAIN-STRUCTURE
LITHIUM-NIOBATE
CRYSTAL
Аннотация: We study the nonlinear Raman–Nath diffraction (NRND) of femtosecond laser pulses in a 1D periodic nonlinear photonic structure. The calculated second-harmonic spectra represent frequency combs for different orders of transverse phase matching. These frequency combs are in close analogy with the well-known spectral Maker fringes observed in single crystals. The spectral intensity of the second harmonic experiences a redshift with a propagation angle, which is opposite the case of Čerenkov nonlinear diffraction. We analyze how NRND is affected by the group-velocity mismatch between fundamental and second-harmonic pulses and by the parameters of the structure. Our experimental results prove the theoretical predictions.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fedorov A. S., Kuzubov A. A., Eliseeva N. S., Popov Z. I., Visotin M. A., Galkin N. G.
Заглавие : Theoretical study of the lithium diffusion in the crystalline and amorphous silicon as well as on its surface
Коллективы : Asian School-Conference on Physics and Technology of Nanostructured Materials, Азиатская школа-конференция по физике и технологии наноструктурированных материалов
Место публикации : Solid State Phenom.: Selected, peer reviewed papers/ ed. N. Galkin: Trans Tech Publications, 2014. - Vol. 213: Physics and Technology of Nanostructured Materials II. - P.29-34. - ISSN 1662-9779, DOI 10.4028/www.scientific.net/SSP.213.29. - ISSN 978-3-03785-970-4
Примечания : Cited References: 21
Ключевые слова (''Своб.индексиров.''): ab initio calculations--diffusion--lithium-ion accumulators--silicon
Аннотация: Using the PAW DFT-GGA method and numerical solving of master equation the diffusion rates of lithium atoms inside both crystal and amorphous silicon of LixSi (x= 0.0.5) composition have been calculated for different temperatures. It is shown the diffusion rate for amorphous silicon is ~10 times greater than that for the crystal silicon. For both structures the rate is increased by 1.5-2 orders of magnitude while the lithium concentration is increased up to 0.5 value. This should result in that the LixSi/Si interface will be sharp. This fact has been further confirmed using molecular dynamic calculations based on Angular Dependent Potential (ADP) model. Also binding energies of Li atoms lying on different sites of Si (001) surface as well as the potential barriers for the atom jumps both along the surface and in the subsurface layers have been calculated. The data show the Li atoms move along the surface very easily but their jumps into subsurface layers are very difficult due to the high potential barrier values. В© (2014) Trans Tech Publications, Switzerland.
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20.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Fedorov A. S., Kuzubov A. A., Eliseeva N. S., Popov Z. I.
Заглавие : Theoretical study of the lithium diffusion in the crystalline and amorphous silicon, as well as on its surface at different lithium concentrations
Коллективы : Asian School-Conference on Physics and Technology of Nanostructured Materials, Азиатская школа-конференция по физике и технологии наноструктурированных материалов
Место публикации : Asian School-Conference on Physics and Technology of Nanostructured Materials. - 2013. - P.133-134
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