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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vorobyev S. A., Saikova S. V., Erenburg S. B., Trubina S. V., Ivanov Y. N., Maksimov N. G., Mikhlin Y. L.
Заглавие : A comparative study of the structure of copper and lead xanthates
Место публикации : J. Struct. Chem. - 2017. - Vol. 58, Is. 6. - P.1144-1151. - ISSN 00224766 (ISSN), DOI 10.1134/S0022476617060117
Примечания : Cited References: 38
Ключевые слова (''Своб.индексиров.''): copper xanthate--lead xanthate--dixanthogen--structure--xps--exafs--solid state nmr
Аннотация: XPS, PbL3 and CuK EXAFS, solid state NMR, and EPR techniques are used to study insoluble products formed in the interaction of aqueous solutions of lead(II) nitrate and copper (II) sulfate with potassium nbutylxanthate (KX). The XPS spectra of lead xanthates with the composition PbX2 are similar to those of KX, and interatomic distances of 0.279 nm suggest a nearly ionic character of Pb–S bonds. In copper xanthate precipitating together with dixanthogen (approximately 15 wt.%), the Cu(I)–S bond length is smaller (0.229 nm), and copper coordination number of 2.9 in a composite with dixanthogen increases to 3.3 after its removal by washing with acetone. The XPS spectra indicate the covalent character of the bond and non-equivalence of xanthate radicals. Solid state 1H and 13C NMR spectra as well as the actual absence of metal lines under the measurement conditions demonstrate strong disordering of the structure of xanthates, which is stronger for PbX2 and weakest in CuX after the removal of dixanthogen. EPR reveals sulfur-containing radicals and Cu2+ in CuX, however, their amounts are insignificant and decrease after the washing with acetone. The results of the work are significant for the understanding of the reactivity of xanthates, in particular, under the conditions of flotation of base metal ores.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lundin A. A., Zobov V. E.
Заглавие : Asymptotic similarity of time correlation functions and shape of the 13C and 29Si NMR spectra in diamond and silicon
Коллективы : Institute of Chemical Physics of the Russian Academy of Science [0082-2018-0005, TSITIS AAAA-A18-118020690203]
Место публикации : J. Exp. Theor. Phys. - 2018. - Vol. 127, Is. 2. - P.305-315. - ISSN 1063-7761, DOI 10.1134/S1063776118080216. - ISSN 1090-6509(eISSN)
Примечания : Cited References: 47. - We thank V.A. Atsarkin, V.V. Demidov, F.S. Dzheparov, and E. B. Feldman for the discussion of our results. This work was supported by a subsidy allocated by the Institute of Chemical Physics of the Russian Academy of Science for the State assignment, theme 0082-2018-0005, code TSITIS AAAA-A18-118020690203.
Предметные рубрики: SPIN SYSTEMS
LINE-SHAPES
RELAXATION
SOLIDS
PARAMAGNETS
RESONANCE
Аннотация: Based on the proposed theory, we have investigated the shape of the NMR absorption spectra for 13C and 29Si nuclei in diamond and silicon crystals attributable to the internuclear dipole–dipole interaction. In accordance with the available experimental data, we have considered both crystals with a 100% content of magnetoactive isotopes and crystals with a comparatively low dilution by nonmagnetic nuclei. The time correlation functions (the first of which is the Fourier transform of the NMR spectrum) arising in an infinite chain of coupled differential equations are shown to be mutually similar with a slight time delay. The proposed theory allows the spectrum to be calculated analytically. The results obtained agree satisfactorily with the experimental ones. It is noted that the mutual similarity of the time correlation functions is probably a corollary of the development of dynamical chaos in the system.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ivanov Y. N., Sukhovskii A. A., Volkov N. V.
Заглавие : B-11 NMR study of Ho1−x Y x Al3(BO3)4 multiferroics
Место публикации : J. Struct. Chem. - 2013. - Vol. 54, Is. 1: Suppl. - P.130-136. - DOI 10.1134/S0022476613070135
Аннотация: The 11B NMR method is used to study the crystals of trigonal alumina borates Ho1−x Y x Al3(BO3)4 (x = 0, 0.5, 1). The temperature-field evolution of quadrupole and hyperfine interactions in these compounds is studied and described.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Yasuda Y., Nakamura H., Fujii Y., Kikuchi H., Chiba M., Yamamoto Y., Hori H., Petrakovskii G. A., Popov M. A., Bezmaternykh L. N.
Заглавие : B-11-NMR study of low-temperature phase transition in CuB2O4
Разночтения заглавия :авие SCOPUS: 11B-NMR study of low-temperature phase transition in CuB 2O4
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2007. - Vol. 19: International Conference on Highly Frustrated Magnetism (AUG 15-19, 2006, Osaka, JAPAN), Is. 14. - Ст.145277. - ISSN 0953-8984, DOI 10.1088/0953-8984/19/14/145277
Примечания : Cited References: 10
Предметные рубрики: COPPER METABORATE
Ключевые слова (''Своб.индексиров.''): copper compounds--low temperature effects--magnetic field effects--nuclear magnetic resonance--b t phase diagram--dzialoshinskii moriya interaction--phase transitions
Аннотация: The material CuB2O4 presents a variety of phases in the B - T phase diagram, caused by the frustration and the Dzialoshinskii - Moriya interaction. In order to investigate the nature of the phase transitions, a B-11- NMR experiment on CuB2O4 has been performed under an applied magnetic field along the a- axis down to 0.4 K. A new incommensurate - incommensurate phase transition has been found at 0.8 K under a field of 0.5 T. Further, another phase transition has been observed at 4.7 K under a field of about 2 T, which is consistent with the transition reported by the neutron diffraction experiment.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrova I.P., Ivanov Yu.N., Bondarev V.S., Sukhovskiy A.A., Voronov V.N.
Заглавие : Calorimetric and 23Na MAS NMR Study of the Phase Diagram of NaNb1-xTaxO3 Solid Solutions
Место публикации : Functional mate rials. - 2010. - Vol. 17. - С. 18-24
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrova I. P., Ivanov Y. N., Bondarev V. S., Sukhovskii A. A., Voronov V. N.
Заглавие : Calorimetric and 23Na MAS NMR study of the phase diagram of NANB1_xTAxO3 solid solutions
Место публикации : Functional Materials. - 2010. - Vol. 17, Is. 1. - P.18-23. - ISSN 1027-5495
Аннотация: The heat capacity of NaNb1_xTaxO3 solid solutions was measured in the temperature range 100 to 770 K. The step-like change of phase transition temperature is observed in the T-x phase diagram at concentration x = 0.55. The obtained results are in a good agreement with the data of dielectric studies. The 23Na MAS NMR spectra were obtained at Larmor frequency 79.35 MHz using a Bruker AVANCE 300 spectrometer. The quadru-polar coupling constant, (CQ=e2qQ/h) and asymmetry parameter (n) were determined by computer fitting of the NMR line shape using the DMFit software. The found parameters show that solid solution structure is NaTa03-based at 0.7<X ?1 and NaNbO3-based at 0?x?0.5. The spectra in the intermediate region (0.5<x?0.7) can be described at a reasonable accuracy when assuming the coexistence of NaTaO3 and NaNbO3 structures. В© 2010 - STC "Institute for Single Crystals".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gabrienko A. A., Morozov E. V., Subramani V., Martyanov O. N., Kazarian S. G.
Заглавие : Chemical visualization of asphaltenes aggregation processes studied in situ with ATR-FTIR spectroscopic imaging and NMR imaging
Коллективы : Skolkovo Foundation; BP
Место публикации : J. Phys. Chem. C: American Chemical Society, 2015. - Vol. 119, Is. 5. - P.2646-2660. - ISSN 1932-7447, DOI 10.1021/jp511891f
Примечания : Cited References:78. - This research was performed under the UNIHEAT project. The authors wish to acknowledge the Skolkovo Foundation and BP for financial support. The authors thank BP for providing samples of crude oil
Предметные рубрики: MEXICAN CRUDE OILS
X-RAY-DIFFRACTION
INFRARED-SPECTROSCOPY
PETROLEUM ASPHALTENES
MOLECULAR-DYNAMICS
VARIABLE SELECTION
ORGANIC-SOLVENTS
LIGHT-SCATTERING
N-HEPTANE
NEAR-IR
Аннотация: Crude oil phase behavior and asphaltene precipitation have been studied by two complementary chemical imaging methods for the first time. ATR-FTIR spectroscopic imaging approach has revealed the chemical composition of agglomerated and precipitated asphaltenes upon dilution with a flocculant. Asphaltenes, containing oxygen and nitrogen heteroatomic functional groups, have been detected to be least stable. Aromatic abundant asphaltenes have been observed to have relatively high solubility in crude oil/heptane blends. NMR imaging approach, capable of imaging in the bulk of crude oil samples, has demonstrated that n-heptane causes aggregation which can lead to the stable suspension or to the sedimentation followed by the formation of deposits, depending on flocculant concentration. These processes have been monitored for small and large amounts of heptane added to crude oil. The data obtained by ATR-FTIR spectroscopic imaging and NMR imaging have been correlated to propose a possible link between the chemical structure of asphaltenes and a mechanism of the formation of deposits.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Antonova A.B., Chudin O.S., Pavlenko N.I., Sokolenko W.A., Rubaylo A.I., Vasiliev A. D., Verpekin V.V., Semeikin O.V.
Заглавие : Chemistry of vinylidene complexes
Место публикации : Russ. Chem. Bull. - NEW YORK: SPRINGER, 2009. - Vol. 58, Is. 5. - С. 955-963. - MAY. - ISSN 1066-5285, DOI 10.1007/s11172-009-0122-3
Примечания : Cited Reference Count: 35. - Гранты: This work was financially supported by the Krasnoyarsk Regional Science Foundation (Grants Nos. 10TS145 and 17G002), the Council on Grants at the President of the Russian Federation (Program for State Support of Leading Scientific Schools, Grant NSh-4137.2006.2), and the Presidium of the Russian Academy of Sciences (Program for Basic Research, Project No. 18.18).Финансирующая организация: Krasnoyarsk Regional Science Foundation [10TS145, 17G002]; Council on Grants at the President of the Russian Federation [NSh-4137.2006.2]; Presidium of the Russian Academy of Sciences [18.18]
Предметные рубрики: RAY CRYSTAL-STRUCTURE
MOLECULAR-STRUCTURE
PHENYLVINYLIDENE LIGANDS
BRIDGED COMPLEXES
TRANSITION-METALS
CARBONYL LIGAND
BINUCLEAR
DERIVATIVES
DINUCLEAR
RHENIUM
Ключевые слова (''Своб.индексиров.''): vinylidene complexes--heterometallic complexes--manganese--rhenium--palladium--platinum--ir and nmr spectroscopy--x-ray diffraction study--heterometallic complexes--ir and nmr spectroscopy--manganese--palladium--platinum--rhenium--vinylidene complexes--x-ray diffraction study
Аннотация: The reactions of Cp(CO)(2)Re=C=CHPh (2) with M(PPh(3))(4) (M = Pd, Pt) gave the mu-vinylidene complexes Cp(CO)(2)RePd(mu-C=CHPh)(PPh(3))(2) (3) and Cp(CO)(2)RePt(mu-C=CHPh)(PPh(3))(2) (1), respectively. The substitution of Ph(2)PCH(2)PPh(2) (dppm) for the PPh(3) ligands in 1 resulted in the formation of Cp(CO)RePt(mu-C(1)=C(2)HPh)(mu-CO)(dppm) (4). The structure of complex 4 has been determined by single-crystal X-ray diffraction analysis. The structural and spectroscopic characteristics of complexes 1, 3, and 4 were compared with the corresponding parameters of the manganese-containing analogs Cp(CO)(2)MnPd(mu-C=CHPh)(PPh(3))(2) (5), Cp(CO)(2)MnPt(mu-C=CHPh)(PPh(3))(2) (6) and Cp(CO)(2)MnPt(mu-C=CHPh)(dppm) (7).
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chudin O. S., Verpekin V. V., Kondrasenko A. A., Burmakina G. V., Piryazev D. A., Vasiliev A. D., Pavlenko N. I., Zimonin D. V., Rubaylo A. I.
Заглавие : Chemistry of vinylidene complexes. XXV. Synthesis and reactions of binuclear µ-vinylidene RePt complexes containing phosphite ligands. Spectroscopic, structural and electrochemical study
Место публикации : Inorg. Chim. Acta. - 2020. - Vol. 505. - Ст.119463. - ISSN 00201693 (ISSN), DOI 10.1016/j.ica.2020.119463
Примечания : Cited References: 56. - This work was conducted within the framework of the budget project AAAA-A17-117021310221-7 for Institute of Chemistry and Chemical Technology SB RAS using the equipment of Krasnoyarsk Regional Research Equipment Centre of SB RAS
Аннотация: Reactions of Cp(CO)2ReCCHPh with Pt[P(OR)3]4 (R = Pri, Et, Ph) gave binuclear μ-vinylidene complexes Cp(CO)2RePt(μ-CCHPh)[P(OR)3]2. Treatment of the previously synthesized Cp(CO)2Re(μ-CCHPh)Pt(PPh3)2 with triisopropylphosphite or triethylphosphite resulted in a stepwise substitution of PPh3 ligands, leading to the disubstituted Cp(CO)2RePt(μ-CCHPh)[P(OR)3]2 and monosubstituted Cp(CO)2RePt(μ-CCHPh)[P(OR)3](PPh3) (R = Pri or Et) species, while no triphenylphosphine ligand substitution in the reaction with P(OPh)3 occurs at all. The monosubstituted Cp(CO)2RePt(μ-CCHPh)[P(OR)3](PPh3) (R = Pri, Et, Ph) species were also obtained by reacting Cp(CO)2ReCCHPh with mixed-ligand complexes Pt(PPh3)3L (L = P(OPri)3, P(OEt)3, P(OPh)3). Reactions of Cp(CO)2RePt(μ-CCHPh)LL′ (L = L′ = P(OPri)3, P(OEt)3, P(OPh)3; L = P(OPri)3, P(OEt)3, P(OPh)3, L′ = PPh3) with Co2(CO)9 yield tricarbonyl vinylidene species Cp(CO)2RePt(μ-CCHPh)[P(OR)3](CO) (R = Pri, Et, Ph). The obtained compounds were characterized by IR and 1H, 13C, 31P NMR spectroscopy. The molecular structures of Cp(CO)2RePt(μ-CCHPh)[P(OPri)3]2, Cp(CO)2RePt(μ-CCHPh)[P(OPri)3](PPh3) and Cp(CO)2RePt(μ-CCHPh)[P(OPri)3](CO) were determined by X-ray diffraction study. The redox properties of the new complexes and their reactions of chemical oxidation were studied.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ioganson A.A., Antonova A.B., Deikhina N.A., Pogrebnyakov D.A., Pavlenko N.I., Burmakina G.V., Rubailo A.I., Petrovskii P.V., Ginzburg A.G.
Заглавие : Chemistry of vinylidene complexes: XIV. Synthesis and NMR and IR study of heterometallic PdMn, PdFe2, and PdFe3 complexes with Ph2PCH2CH2PPh2 chelating ligand
Место публикации : Russian Journal of General Chemistry. - Санкт-Петербург: Pleiades Publishing, Ltd. (Плеадес Паблишинг, Лтд), 1999. - Т. 69, № 6. - С. 847-855. - ISSN 1070-3632. - ISSN 1608-3350(eissn)
ГРНТИ : 31.17
РИНЦ
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Falaleev O. V., Falaleeva L. G.
Заглавие : Cross-singular dips in the NMR absorption line of polycrystals with isolated spin pairs
Место публикации : JETP Letters. - 1998. - Vol. 68, Is. 1. - P.101-106. - ISSN 0021-3640, DOI 10.1134/1.567828
Примечания : Cited References: 21
Предметные рубрики: F-19 NMR
Аннотация: Cross-singular dips at the center of the spectra of polycrystals of Fake systems, i.e., systems containing well-isolated pair groupings, are obtained by numerical calculations of the NMR absorption line for a 10-spin (I=1/2) model. The physical reason for such dips is the behavior of the flip-flop component of the interpair dipole-dipole interactions ("6/5 factor"). Cases of experimental manifestation of cross-singular dips are noted. (C) 1998 American Institute of Physics.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Lundin A. A.
Заглавие : Decay of Multispin Multiple-Quantum Coherent States in the NMR of a Solid and the Stabilization of Their Intensity Profile with Time
Разночтения заглавия :авие SCOPUS: Decay of multispin multiple-quantum coherent states in the NMR of a solid and the stabilization of their intensity profile with time
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 113, Is. 6. - P1006-1014. - ISSN 1063-7761, DOI 10.1134/S1063776111140111
Примечания : Cited References: 27
Ключевые слова (''Своб.индексиров.''): cluster sizes--coherent state--decay rate--effective size--experimental data--intensity profiles--coherent light--decay (organic)--stabilization
Аннотация: Variations, experimentally observed in [14], in the intensity profiles of multiple-quantum (MQ) coherences in the presence of two special types of perturbations are explained on the basis of the theory, earlier developed by the authors, of the growth of the effective size of correlated clusters (the number of correlated spins) and the relaxation of MQ coherent states [23]. The intensity and the character of perturbation were controlled by the experimenters. It is shown that the observed stabilization of profiles with time is not associated with the stabilization of the cluster size. Quite the contrary, a cluster of correlated spins monotonically grows, while the observed variations in the intensity profile and its stabilization with time are attributed to the dependence of the decay rate of an MQ coherence on its order (its position in the MQ spectrum). The results of the theory are in good agreement with the experimental data.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Lundin A. A.
Заглавие : Decay of multispin multiquantum coherent states in the NMR of a solid
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 112, Is. 3. - P451-459. - ISSN 1063-7761, DOI 10.1134/S1063776111020129
Примечания : Cited References: 24
Предметные рубрики: SYSTEMS
SPECTRA
Ключевые слова (''Своб.индексиров.''): adiabatic approximations--andersons--coherent state--dynamic phenomena--experimental data--local fields--model-based--radiospectroscopy--relaxation functions--spin precession--theoretical result--two-component--coherent light
Аннотация: A model based on the Anderson adiabatic approximation, which is widely used for describing various aspects of dynamic phenomena in conventional radiospectroscopy, is proposed for describing the decay of multispin multiquantum coherent states in a solid. The coherent state relaxation function is represented by the product of two functions corresponding to spin precession in a two-component local field with a correlated and an uncorrelated component. Theoretical results of this study explain the experimental data reported in a number of publications and are in good agreement with these data.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lundin A. A., Zobov V. E.
Заглавие : Decoherence-induced stabilization of the multiple-quantum NMR-spectrum width
Место публикации : Appl. Magn. Reson.: Springer, 2016. - Vol. 47, Is. 7. - P.701-710. - ISSN 0937-9347, DOI 10.1007/s00723-016-0770-z. - ISSN 1613-7507(eISSN)
Примечания : Cited References:26
Предметные рубрики: SIMULATIONS
DYNAMICS
SYSTEMS
SOLIDS
Аннотация: The time dependence of an increase in the number of correlated spins in cluster was calculated for a particular variant of multiple-quantum (MQ) nuclear magnetic resonance spectroscopy using an effective two-quantum Hamiltonian that includes conventional secular nuclear dipole-dipole interaction as a weak perturbation at the stage of correlation preparation. It was shown that the cluster size grows steadily, while the width of the MQ spectrum stabilizes because the decay rates of the spectral components located at different areas of the MQ spectrum are different. The MQ bandwidth was also calculated as a function of the preparation time for various perturbation strengths. The results obtained are in excellent agreement with the experimental data reported in Alvarez and Suter (Phys Rev A 84:012320, 2011).
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Belyaev B. A., Drokin N. A., Kumakhov M. A., Shabanov V. F.
Заглавие : Dielectric properties of liquid crystals in polycapillary matrices
Коллективы :
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2010. - Vol. 52, Is. 6. - P1315-1322. - ISSN 1063-7834, DOI 10.1134/S1063783410060314
Примечания : Cited References: 24. - This study was supported by the Council on Grants from the President of the Russian Federation (grant no. 3818.2008.3) and the Siberian Branch of the Russian Academy of Sciences (Integration Project no. 5) and performed within the framework of the State Contract (no. 02.740.11.0220).
Предметные рубрики: MOLECULAR-SIEVES
SILICA AEROGEL
POROUS-GLASS
MEMBRANES
NMR
8CB
Аннотация: This paper reports on the results of investigations into the dielectric properties of liquid crystals embedded in polycapillary matrices and describes a technique for their measurement. It has been revealed that the chemical structure of the rigid core and the length of mobile alkyl groups of liquid-crystal molecules of the alkylcyanobiphenyl group substantially affect the equilibrium configuration of the liquid-crystal director in capillaries. The reorientation of liquid-crystal molecules embedded in capillaries in the nematic phase under the influence of an external magnetic field has been investigated.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : TSIFRINOVICH V. I.
Заглавие : DYNAMIC FREQUENCY-SHIFT OF QUADRUPOLE SPLITTED NMR-SPECTRA
Место публикации : Zhurnal Eksperimentalnoi Teor. Fiz.: MEZHDUNARODNAYA KNIGA, 1987. - Vol. 92, Is. 4. - P1394-1400. - ISSN 0044-4510
Примечания : Cited References: 12
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : TSIFRINOVICH V. I.
Заглавие : DYNAMIC NMR FREQUENCY-SHIFT IN THE INVERTED STATE
Место публикации : Zhurnal Eksperimentalnoi Teor. Fiz.: MEZHDUNARODNAYA KNIGA, 1982. - Vol. 83, Is. 2. - P715-717. - ISSN 0044-4510
Примечания : Cited References: 5
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Eremin I.
Заглавие : Dynamical magnetic susceptibility in the lamellar cobaltate superconductor NaxCoO2 center dot yH(2)O
Разночтения заглавия :авие SCOPUS: Dynamical magnetic susceptibility in the lamellar cobaltate superconductor Nax Co O2 y H2 O
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2008. - Vol. 77, Is. 6. - Ст.64510. - ISSN 1098-0121, DOI 10.1103/PhysRevB.77.064510
Примечания : Cited References: 49
Предметные рубрики: UNCONVENTIONAL SUPERCONDUCTIVITY
NMR
Аннотация: We systematically analyze the influence of the superconducting gap symmetry and the electronic structure on the dynamical spin susceptibility in superconducting NaxCoO2 center dot yH(2)O within three different models: The single a(1g)-band model with nearest-neighbor hoppings, the realistic three-band t(2g) model with, and without e(g)' pockets present at the Fermi surface. We show that the magnetic response in the normal state is dominated by the incommensurate antiferromagnetic spin density wave fluctuations at large momenta in agreement with experimental temperature dependence of the spin-lattice relaxation rate. Also, we demonstrate that the presence or the absence of the e(g)' pockets at the Fermi surface does not significantly affect this conclusion. In the superconducting state our results for d(x)(2)-y(2)- or d(xy)-wave symmetries of the superconducting order parameter are consistent with experimental data and exclude nodeless d(x)(2)-y(2)+id(xy)-wave symmetry. We further point out that the spin-resonance peak proposed earlier is improbable for the realistic band structure of NaxCoO2 center dot yH(2)O. Moreover, even if present the resonance peak is confined to the antiferromagnetic wave vector and disappears away from it.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Morozov E. V., Trukhan, Sergey N., Kozhevnikov, Ivan V., Peterson, Ivan V., Martyanov, Oleg N.
Заглавие : Dynamics of asphaltene aggregates under high-pressure CO2 revealed by pulsed-field gradient NMR
Колич.характеристики :12 с
Место публикации : Energy & Fuels. - 2023. - Vol. 37, Is. 22. - P.17215-17226. - ISSN 08870624 (ISSN), DOI 10.1021/acs.energyfuels.3c02862. - ISSN 15205029 (eISSN)
Примечания : Cited References: 90. - The present research was performed with the financial support of the Russian Science Foundation (project no. 21-13-00171, http://rscf.ru/project/21-13-00171/) using the equipment of the Krasnoyarsk Regional Center of Research Equipment of the Federal Research Center “Krasnoyarsk Science Center SB RAS”
Аннотация: The work demonstrates the results of the first experimental PFG NMR study in situ of the complex phase behavior of asphaltenes in the presence of high-pressure CO2. To perform the experiments, a series of sealed, thick-walled quartz capillaries were prepared with a mixture of CO2 and asphaltenes dissolved either in chloroform or benzene at different initial concentrations. Then, the temperature dependence of the diffusion coefficients of the asphaltene aggregates was measured for each sample after the mixture reached its equilibrium state, at which, in accordance with the solubility limit, only part of the initial asphaltenes remained dissolved. Despite quite low residual asphaltene concentrations in solution, experimental data clearly demonstrated the presence of aggregated structures (up to 70–80 wt %) attributed solely to nanoaggregates, with no signs of the presence of macroaggregates in the samples. Temperature dependencies of aggregate diffusivity clearly showed that the scenario, according to which the evolution of the asphaltene aggregates will develop, strongly depends on the initial asphaltene concentration, mass fraction of CO2 loaded into the system, and chemical nature of the solvent used. In particular, the most diluted asphaltene solution, expected to be the most resistive to the aggregation processes in a high-pressure CO2 environment, revealed the most pronounced aggregation-dependent translational dynamics as compared to those with a moderate initial asphaltene concentration. Contrarily, the concentrated asphaltene solution may not show drastic aggregation processes if the mass fraction of the CO2 loaded will not appear to be so high. Finally, the experimental results provide evidence that the temperature-triggered structural transformation of asphaltene aggregates due to the noncovalent bond breakup is not hindered under high-pressure CO2, but instead becomes more emphasized. The results obtained shed new light on asphaltene aggregate dynamics and brought new knowledge about the fundamental behavior of asphaltene in high-pressure CO2 conditions.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Lundin A. A.
Заглавие : Effect of degradation processes caused by a small perturbation on the growth of the average cluster size of correlated spins in multiple quantum NMR spectroscopy of solids
Место публикации : Appl. Magn. Reson. - 2021. - Vol. 52. Is. 7. - P.879–892. - ISSN 09379347 (ISSN), DOI 10.1007/s00723-021-01342-1
Примечания : Cited References: 33. - The study is funded by the Ministry of Science and Higher Education of the Russian Federation in the framework of the State assignment, State registration number AAAA-A19-119012890064-7
Аннотация: Multiple quantum (MQ) NMR spectroscopy of solids allows one to observe the growth and decay of multispin correlations. As a rule, the average size of the cluster of correlated spins is extracted from the width of the MQ spectrum. In the present article, the size distribution of such clusters is explored. To obtain the above distribution, the solutions for the amplitudes of the decomposition over complete sets of orthogonal operators for the two different models were used. By means of these models, we have taken into account the dependence of cluster degradation (the degradation of a cluster means, e.g., destruction of correlations in cluster or loss of particles in it) through two positions. The first one defines by the cluster size while the second one depends on the MQ coherence order of the cluster. It is shown that in dependence of the relation the rates of these degradation processes, the width of the MQ spectrum carries different information. If the first process is faster that the second one, then the width of the MQ spectrum is still determined by the average cluster size. When the velocity ratio becomes inverse, the width of the MQ spectrum takes on a smaller value, which is a consequence of the faster degradation of the MQ spectrum components with large orders of coherence.
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