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Fractal dimension of cluster boundaries in porous polycrystalline HTSC materials / A. A. Bykov [et al.] // Phys. Solid State. - 2012. - Vol. 54, Is. 10. - P. 1947-1950, DOI 10.1134/S1063783412100095. - Cited References: 20 . - ISSN 1063-7834

РУБ Physics, Condensed Matter
Рубрики:
CURRENT-VOLTAGE CHARACTERISTICS
   ELECTRICAL-CONDUCTIVITY
   PERCOLATION
   MIXTURES
   MEDIA
   SUPERCONDUCTORS
   TRANSPORT
   SPHERES
Аннотация: The fractal dimension of the boundaries of clusters formed by pores and granules in polycrystalline materials is shown to be determined by the sample density and crystallite sizes. The dependence of the fractal dimension on the density has a maximum. It is shown that the maximum diamagnetic response can be obtained in a porous high-temperature superconductor with a porosity of 50-60% and small crystallite sizes.

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Публикация на русском языке Фрактальная размерность границ кластеров в пористых поликристаллических ВТСП-материалах [Текст] / А. А. Быков [и др.] // Физ. тверд. тела : Физико-технический институт им. А.Ф.Иоффе РАН, 2012. - Т. 54 Вып. 10. - С. 1825-1828

Держатели документа:
[Bykov, A. A.
Terent'ev, K. Yu.
Gokhfeld, D. M.
Petrov, M. I.] Russian Acad Sci, Siberian Branch, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia

Доп.точки доступа:
Bykov, A. A.; Быков, Алексей Анатольевич; Terent'yev, K. Yu.; Терентьев, Константин Юрьевич; Gokhfeld, D. M.; Гохфельд, Денис Михайлович; Petrov, M. I.; Петров, Михаил Иванович
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    Normal and superconducting properties of cuprates in multielectron theory / S. Ovchinnikov [et al.] // J. Supercond. Nov. Magn. - 2013. - Vol. 26, Is. 9. - P. 2831-2835, DOI 10.1007/s10948-013-2263-8 . - ISSN 1557-1939
   Перевод заглавия: Нормальные и сверхпроводящие свойства купратов в многоэлектронной теории
Кл.слова (ненормированные):
Cluster perturbation theory -- Fermi surface reconstruction -- Strong electron correlations
Аннотация: We consider the doping dependence of the normal and superconducting properties of La2-x Srx CuO4 in the low energy effective model based on the ab initio LDA+GTB calculations. We have found that two quantum phase transitions (QPT) of the Lifshitz type correspond well to the experimental phase diagram. For superconducting state, we have considered both magnetic and phonon mechanisms of pairing. Finally, we compare the true Fermi surface and the spectral intensity map seen in ARPES within a new norm conserving cluster perturbation theory (NC-CPT). В© 2013 Springer Science+Business Media New York.

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Держатели документа:
Russian Acad Sci, LV Kirensky Phys Inst, Siberian Branch, Krasnoyarsk 660036, Russia
Siberian Fed Univ, Krasnoyarsk 660041, Russia
Reshetnev Siberian State Aerosp Univ, Krasnoyarsk 660014, Russia
Dostoyevsky Omsk State Univ, Omsk 644077, Russia;

Доп.точки доступа:
Ovchinnikov, S. G.; Овчинников, Сергей Геннадьевич; Korshunov, M. M.; Коршунов, Максим Михайлович; Nikolaev, S.; Shneyder, E. I.; Шнейдер, Елена Игоревна; Krinitsyn, A.
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Nikolaev, S. V.
Effect of hole doping on the electronic structure and the Fermi surface in the Hubbard model within norm-conserving cluster pertubation theory / S. V. Nikolaev, S. G. Ovchinnikov // J. Exp. Theor. Phys. - 2012. - Vol. 114, Is. 1. - P. 118-131, DOI 10.1134/S1063776111150143. - Cited References: 51. - This study was supported financially by the Russian Foundation for Basic Research (project nos. 10-02-90725-mob_st and 09-02-00127), Program 18.7 of the Presidium of the Russian Academy of Sciences, the Federal Target Program "Personnel" (state contract no. P891), and the integrated project no. 40 of the Siberian Branch of the Russian Academy of Sciences. . - ISSN 1063-7761

РУБ Physics, Multidisciplinary
Рубрики:
HIGH-TEMPERATURE SUPERCONDUCTORS
   NARROW ENERGY-BANDS
   CORRELATED ELECTRONS
   PSEUDOGAP
   EVOLUTION
   La2-XSRXCuO4
   INSULATOR
Аннотация: The concentration dependences of the band structure, spectral weight, density of states, and Fermi surface in the paramagnetic state are studied in the Hubbard model within cluster pertubation theory with 2 x 2 clusters. Representation of the Hubbard X operators makes it possible to control conservation of the spectral weight in constructing cluster perturbation theory. The calculated value of the ground-state energy is in good agreement with the results obtained using nonperturbative methods such as the quantum Monte Carlo method, exact diagonalization of a 4 x 4 cluster, and the variational Monte Carlo method. It is shown that in the case of hole doping, the states in the band gap (in-gap states) lie near the top of the lower Hubbard band for large values of U and near the bottom of the upper band for small U. The concentration dependence of the Fermi surface strongly depends on hopping to second (t') and third (t '') neighbors. For parameter values typical of HTSC cuprates, the existence of three concentration regions with different Fermi surfaces is demonstrated. It is shown that broadening of the spectral electron density with an energy resolution typical of contemporary ARPES leads to a pattern of arcs with a length depending on the concentration. Only an order-of-magnitude decrease in the linewidth makes it possible to obtain the true Fermi surface from the spectral density. The kinks associated with strong electron correlations are detected in the dispersion relation below the Fermi level.

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Публикация на русском языке Николаев, Сергей Викторович. Влияние дырочного допирования на электронную структуру и поверхность ферми в модели хаббарда в рамках кластерной теории возмущений с контролируемым спектральным весом [Текст] / С. В. Николаев, С. Г. Овчинников // Журн. эксперим. и теор. физ. : Наука, 2012. - Т. 141 Вып. 1. - С. 135-150

Держатели документа:
[Nikolaev, S. V.
Ovchinnikov, S. G.] Russian Acad Sci, Kirensky Inst Phys, Siberian Branch, Krasnoyarsk 660036, Russia
[Nikolaev, S. V.] Dostoevsky State Univ, Omsk 644077, Russia
[Ovchinnikov, S. G.] Siberian Fed Univ, Krasnoyarsk 660041, Russia

Доп.точки доступа:
Ovchinnikov, S. G.; Овчинников, Сергей Геннадьевич; Николаев, Сергей Викторович
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Krinitsyn, A.
Cluster size and shape effect on the electronic structure of the Hubbard model within the norm-conserving cluster perturbation theory / A. Krinitsyn, S. Nikolaev, S. G. Ovchinnikov // J. Supercond. Nov. Magn. - 2014. - Vol. 27, Is. 4. - P. 955-963, DOI 10.1007/s10948-013-2418-7. - Cited References: 59. - This work was supported by Grants NSh-1044.2012.2 and MK-1168.2012.2, Siberian Federal University: Grant F-11, and the Presidium of RAS Program 20.7. . - ISSN 1557-1939. - ISSN 1557-1947

РУБ Physics, Applied + Physics, Condensed Matter
Рубрики:
NARROW ENERGY-BANDS
   CUPRATE SUPERCONDUCTORS
   PHOTOEMISSION SPECTRA
   PSEUDOGAP
   ANTIFERROMAGNET
   EXCITATIONS
   EVOLUTION
   SYSTEMS
   PHASE
   STATE
Кл.слова (ненормированные):
Cluster perturbation theory -- Hubbard model -- Strong correlations -- Density of states -- Fermi surface
Аннотация: Within a new norm-conserving approach to the cluster perturbation theory (CPT) for the 2d Hubbard model we study the effect of the cluster size and shape on the electronic structure. We have compared two type of clusters, 4-cluster (2x2) and 5-cluster (cruciform of 5 atoms). With 4-cluster we can treat exactly the first and second neighbours correlations, C (1) and C (2). With 5-cluster the third neighbour correlations C (3) are also treated exactly. The band structure in the CPT with 4- and 5-clusters differs remarkably. The quasiparticle spectral weight map for 5-clusters is very similar to the Quantum Monte Carlo (QMC) and the variational CPT data. With increasing doping, small hole Fermi surface transforms into conventional Fermi-liquid type large Fermi surface through Lifshitz quantum phase transitions.

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Держатели документа:
Dostoyevsky Omsk State Univ, Omsk 644077, Russia
Siberian Fed Univ, Krasnoyarsk 660041, Russia
Russian Acad Sci, Kirensky Inst Phys, Siberian Branch, Krasnoyarsk 660036, Russia

Доп.точки доступа:
Nikolaev, S.; Ovchinnikov, S. G.; Овчинников, Сергей Геннадьевич; Siberian Federal University [F-11]; Presidium of RAS Program [20.7]; [NSh-1044.2012.2]; [MK-1168.2012.2]
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Kuz'min, V. I.
Comparison of the electronic structure of the Hubbard and t - J models within the cluster perturbation theory / V. I. Kuz'min, S. V. Nikolaev, S. G. Ovchinnikov // Phys. Rev. B. - 2014. - Vol. 90, Is. 24. - Ст. 245104, DOI 10.1103/PhysRevB.90.245104. - Cited References: 37. - This work is supported by RFBR (Grants No. 13-02-01395-a, No. 14-02-31677-mol-a, and No. 14-02-00186-a), the Ministry of Education and Science of Russia (Government Contract No. 3085, SibFU 2014 GF-2), and a grant of the Russian President (Grant No. NSh-2886.2014.2). . - ISSN 1098-0121. - ISSN 1550-235X

РУБ Physics, Condensed Matter
Рубрики:
FERMION SYSTEMS
SUPERCONDUCTIVITY
METAL
Аннотация: Electronic dispersion and density of states (DOS) have been calculated for the Hubbard model and the t−J and t−J∗ models with three-site correlated hopping by the cluster perturbation theory. We have found a rather strong quantitative difference both in dispersion and DOS at all doping for the Hubbard and t−J models at the energy scale ω≳t. The three-site correlated hopping addition results in an almost negligible difference for the Hubbard and t−J∗ models. Close to the Fermi energy, at the scale ω≲J, the electronic structure of all three models is similar. We have found the line of zeros of the Green function for the t−J model that has been previously obtained for the Hubbard model by cellular dynamical mean-field theory calculations.

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Держатели документа:
SB RAS, LV Kirensky Inst Phys, Krasnoyarsk 660036, Russia
Siberian Fed Univ, Krasnoyarsk 660041, Russia

Доп.точки доступа:
Nikolaev, S. V.; Николаев, Сергей Викторович; Ovchinnikov, S. G.; Овчинников, Сергей Геннадьевич; Кузьмин, Валерий Ипполитович; RFBR [13-02-01395-a, 14-02-31677-mol-a, 14-02-00186-a]; Ministry of Education and Science of Russia [3085, SibFU 2014 GF-2]; [NSh-2886.2014.2]
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    Ivantsov, I. D.
    Cluster perturbation theory for 2d ising model / I. D. Ivantsov, S. G. Ovchinnikov // J. Sib. Fed. Univ. Math. Phys. - 2015. - Vol. 8, Is. 1. - P. 31-37 ; Журн. СФУ. Сер. "Математика и физика". - Cited References: 5. - The authors are grateful to Sergey V. Nikolaev for useful discussions and President of Russia, grant nsh-2886.2014.2 . - ISSN 1997-1397
   Перевод заглавия: Кластерная теория возмущений для двумерной модели Изинга
Кл.слова (ненормированные):
Cluster perturbation theory -- Ising model -- X-operators -- модель Изинга -- кластерная теория возмущений -- Х-операторы
Аннотация: This paper deals with 2d Ising model in the scope of cluster perturbation theory. Ising model is defined on a two-dimensional square lattice, the amount of nearest neighbors z=4. Lattice is divided into clusters of a given size and a complete set of energy eigenvalues and eigenvectors of the cluster is defined by the diagonalization method. On the basis of this, Hubbard operators are constructed and Green function is calculated, taking into account intercluster interactions according to perturbation theory, it allows us to obtain the dependence of the magnetization on the temperature in the Hubbard-I approximation. Obtained results are compared with the exact solution of the two-dimensional Ising model.
В настоящей работе проводится исследование двумерной модели Изинга в рамках кластерной теории возмущений. Модель Изинга задана на двумерной квадратной решетке с числом ближайших соседей z=4. Решетка разбивается на кластеры заданного размера и методом точной диагонализации определяется полный набор собственных значений энергии и собственных векторов кластера. На этом базисе строятся операторы Хаббарда и вычисляется функция Грина с учетом межкластерных взаимодействий по теории возмущений, позволяющая получить зависимость намагниченности от температуры в приближении Хаббард-I. Полученные результаты сравниваются с точным решением двумерной модели Изинга.

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Держатели документа:
Institute of Engineering Physics and Radio Electronics, Siberian Federal University, Svobodny, 79Krasnoyarsk, Russian Federation
Kirensky Institute of Physics, Akademgorodok, 50/38Krasnoyarsk, Russian Federation

Доп.точки доступа:
Ovchinnikov, S. G.; Овчинников, Сергей Геннадьевич; Иванцов, Илья Дмитриевич

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    Molecular structure of a new tetranuclear μ2:μ3-bis-vinylidene cluster, Cp2(CO)4RePd(μ-CCHPh)RePd(μ3-CCHPh)(η2-dppe) / V. V. Verpekin [et al.] // Polyhedron. - 2015. - Vol. 90. - P. 104-107, DOI 10.1016/j.poly.2015.01.028. - Cited References:33. - This work was financially supported by the Presidium of the Russian Academy of Sciences (Program for Basic Research, Project No. 8.15). Authors are grateful to Prof. N.A. Ustynyuk for useful discussions. . - ISSN 0277-5387
   Перевод заглавия: Молекулярная структура нового тетраядерного m2: m3-bis-винилиденового кластера, Cp2(CO)4RePd(m-C=CHPh) RePd(m3-C=CHPh)(h2-dppe)

РУБ Chemistry, Inorganic & Nuclear + Crystallography
Рубрики:
VINYLIDENE-BRIDGED COMPLEXES
TRANSITION-METAL-COMPLEXES
Кл.слова (ненормированные):
Rhenium -- Palladium -- Vinylidene complexes -- Heterometallic complexes -- X-ray diffraction
Аннотация: The novel tetranuclear di-vinylidene complex Cp2(CO)4RePd(μ2-CCHPh)RePd(μ3-CCHPh)(dppe) was isolated and characterized by X-ray diffraction. This cluster consists of two RePd fragments linked to each other through the bonding of the palladium atom in the [Cp(CO)2RePd(μ-CCHPh)] fragment to the carbonyl and vinylidene ligands in the Cp(CO)2RePd(μ-CCHPh)(dppe) fragment.

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Держатели документа:
Russian Acad Sci, Siberian Branch, Inst Chem & Chem Technol, Krasnoyarsk 660036, Russia
Russian Acad Sci, Siberian Branch, Inst Phys, Krasnoyarsk 660036, Russia
RAS, Siberian Branch, Krasnoyarsk Sci Ctr, Krasnoyarsk 660036, Russia
Siberian Fed Univ, Krasnoyarsk 660041, Russia
Russian Acad Sci, AN Nesmeyanov Inst Organoelement Cpds, Moscow 119991, Russia

Доп.точки доступа:
Verpekin, V. V.; Chudin, O. S.; Vasiliev, A. D.; Васильев, Александр Дмитриевич; Kondrasenko, A. A.; Pavlenko, N. I.; Rubaylo, A. I.; Kreindlin, A. Z.; Presidium of the Russian Academy of Sciences [8.15]
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    The exchange interaction effects on magnetic properties of the nanostructured CoPt particles / S. V. Komogortsev [et al.] // J. Magn. Magn. Mater. - 2016. - Vol. 401. - P. 236-241, DOI 10.1016/j.jmmm.2015.10.041. - Cited References: 55. - The work has been partially supported by RFBR Grants 15-08-06673, 14-03-00411, 14-03-00129, 15-42-0417115 and it is partly performed in Siberian Federal University within the state contract of the Russian Federation Ministry of Education and Science for 2014-2016 (project number 1792) . - ISSN 0304-8853
   Перевод заглавия: Влияния обменного взаимодействия на магнитные свойства наноструктурированных частиц CoPt

РУБ Materials Science, Multidisciplinary + Physics, Condensed Matter
Рубрики:
CLUSTER BEAM DEPOSITION
   BULK MAGNETS
   NANOCRYSTALLINE FERROMAGNETS
   REMANENCE ENHANCEMENT
   THIN-FILMS
   COERCIVITY
   MICROSTRUCTURE
   NANOPARTICLES
   IRON
   SYSTEM
Аннотация: Various manifestations of the exchange interaction effects in magnetization curves of the CoPt nanostructured particles are demonstrated and discussed. The inter-grain exchange constant A in the sponge-like agglomerates of crystallites is estimated as A=(7±1) pJ/m from the approach magnetization to saturation curves that is in good agreement with A=(6.6±0.5) pJ/m obtained from Bloch T 3/2 law. The fractal dimensionality of the exchange coupled crystallite system in the porous media of the disordered CoPt alloy d=(2.60±0.18) was estimated from the approach magnetization to saturation curve. Coercive force decreases with temperature as Hc~T 3/2 which is assumed to be a consequence of the magnetic anisotropy energy reduction due to the thermal spin wave excitations in the investigated CoPt particles. © 2015 Elsevier B.V. All rightsreserved.
Демонстрируются и обсуждаются различные проявления эффектов обменного взаимодействия в кривых намагниченности наноструктуированных частиц CoPt. Межзеренная обменная константа А в агломератах губчатой структуры кристаллитов оценивается как /A/=(7±1) pJ/m из кривых приближения намагниченности к насыщению, это значение находится в хорошем согласии с /A/=(6.6±0.5) pJ/m, полученным из закона /T/. /2 Блоха. Размерность фрактала обменно-соединенных кристаллических систем в пористой среды неупорядоченного сплава CoPt /d/=(2.60±0.18) оценивалась из кривых приближения намагниченности к насыщению. Коэрцитивная сила уменьшается с температурой по закону /H_c /~/T/. /2 , который, как предполагается, есть следствие уменьшения энергии магнитной анизотропии из-за теплового возбуждения спиновых волн в изучаемых частицах CoPt.

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Держатели документа:
Kirensky Institute of Physics, SB RAS, Krasnoyarsk, Russian Federation
Nikolaev Institute of Inorganic Chemistry, SB RAS, Novosibirsk, Russian Federation
Novosibirsk State University, Novosibirsk, Russian Federation
Siberian Federal University, Krasnoyarsk, Russian Federation

Доп.точки доступа:
Komogortsev, S. V.; Комогорцев, Сергей Викторович; Iskhakov, R. S.; Исхаков, Рауф Садыкович; Zimin, A. A.; Зимин, А. А.; Filatov, E. Y.; Korenev, S. V.; Shubin, Yu. V.; Chizhik, N. A.; Yurkin, G. Yu.; Юркин, Глеб Юрьевич; Eremin, E. V.; Еремин, Евгений Владимирович
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Nikolaev, S. V.
Electronic structure of the Hubbard and t-J models within the cluster perturbation theory in the X-operators representa / S. V. Nikolaev, V. I. Kuz’min, S. G. Ovchinnikov // V Int. symp. on strong nonlinear vibronic and electronic int. in solids : program, book of abstracts. - 2015. - Ст. O20. - P30. - Библиогр.: 2 назв.

Материалы конференции

Доп.точки доступа:
Kuz’min, V. I.; Ovchinnikov, S. G.; Овчинников, Сергей Геннадьевич
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10.

    Кузьмин, Валерий Ипполитович.
    Исследование аномалий электронной дисперсии в модели Хаббарда, t-J- и t-J*-модели в рамках кластерной теории возмущений в представлении Х-операторов / В. И. Кузьмин, С. В. Николаев // Вестник НГУ. Физика. - 2015. - Т. 10, Вып. 1. - С. 50-56. - Библиогр.: 23. - Работа выполнена при финансовой поддержке Российского научного фонда (проект № 14-12-00061). . - ISSN 1818-7994
   Перевод заглавия: Investigation of anomalies in the electronic dispersion of the Hubbard model, t-J and t-J * models within the cluster perturbation theory in the X-operator representation
Кл.слова (ненормированные):
высокотемпературная сверхпроводимость -- электронная структура купратов -- высокоэнергетические кинки -- кластерные теории -- модель Хаббарда -- t-J-модель -- high-temperature superconductivityory -- electronic structure of cuprates -- high-energy kinks -- cluster perturbation theory -- Hubbard model -- t-J-model
Аннотация: В рамках кластерной теории возмущений в представлении Х-операторов Хаббарда рассчитана энергетическая структура электронов в модели Хаббарда, t-J- и t-J *-модели с учетом уширения спектральных линий, соответствующего экспериментам по фотоэмиссионной спектроскопии с угловым разрешением. При энергиях порядка интеграла перескока t в полученных спектрах наблюдаются аномалии, схожие с высокоэнергетическими кинками, наблюдаемыми в экспериментах по фотоэмиссионной спектроскопии с угловым разрешением. Исследовано поведение высокоэнергетических аномалий электронной дисперсии при изменениях величины допирования и параметра кулоновского отталкивания. Проанализировано влияние трехцентровых коррелированных перескоков на результаты расчета.
The electronic structure with the spectral line broadening corresponding to the angle-resolved photoemission spectroscopy resolution has been calculated for the Hubbard model, t-J and t-J * models within the norm-conserving cluster perturbation theory. The electronic dispersion anomalies similar to the high-energy kinks observed in the angle-resolved photoemission spectroscopy experiments are obtained at the energy scale of order of the hopping integral t. The doping dependence of the high-energy anomalies for different Coulomb repulsion values is discussed. The influence of the three-site correlated hopping on the results is analyzed.

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Держатели документа:
Институт физики им. Л.В. Киренского СО РАН

Доп.точки доступа:
Николаев, Сергей Викторович; Nikolaev, S. V.; Kuz'min, V. I.; Сибирский молодежный семинар по высокотемпературной сверхпроводимости и физике наноструктур – ОКНО 2014 (X ; 13 - 14 ноября 2014 г. ; Новосибирск)
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11.

Kuz'min, V. I.
Comparison of the electronic structure of the Hubbard and t-J models within the cluster perturbation theory / V. I. Kuz’min, S. V. Nikolaev, S. G. Ovchinnikov // Пятая Междунар. конф. "Фундаментал. проблемы высокотемператур. сверхпроводимости" (ФПС’15) : сборник расширенных тезисов. - М. : ФИАН, 2015. - Ст. M7. - С. 58-59

Материалы конференции

Доп.точки доступа:
Nikolaev, S. V.; Николаев, Сергей Викторович; Ovchinnikov, S. G.; Овчинников, Сергей Геннадьевич; Кузьмин, Валерий Ипполитович; "Фундаментальные проблемы высокотемпературной сверхпроводимости", Международная конференция(5 ; 2015 ; окт. ; 5-9 ; Малаховка, Моск. обл.); Российская академия наук; Физический институт им. П.Н. Лебедева РАН; Научный совет по физике конденсированного состояния РАН; Научный совет по физике низких температур РАН
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12.

Zobov, V. E.
Decay of Multispin Multiple-Quantum Coherent States in the NMR of a Solid and the Stabilization of Their Intensity Profile with Time / V. E. Zobov, A. A. Lundin // J. Exp. Theor. Phys. - 2011. - Vol. 113, Is. 6. - P. 1006-1014, DOI 10.1134/S1063776111140111. - Cited References: 27 . - ISSN 1063-7761

РУБ Physics, Multidisciplinary

Кл.слова (ненормированные):
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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Держатели документа:
[Zobov, V. E.] Russian Acad Sci, LV Kirensky Phys Inst, Siberian Branch, Krasnoyarsk 660036, Russia
[Lundin, A. A.] Russian Acad Sci, NN Semenov Chem Phys Inst, Moscow 117977, Russia
ИФ СО РАН
Kirensky Institute of Physics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk, 660036, Russian Federation
Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow, 117977, Russian Federation

Доп.точки доступа:
Lundin, A. A.; Зобов, Владимир Евгеньевич
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13.

Ovchinnikov, S. G.
Calculation of the Fermi Surface with Complex Topology from Norm-Conserving Cluster Perturbation Theory for Doping Dependent Electronic Structure of the Hubbard Model / S. G. Ovchinnikov, S. V. Nikolaev // JETP Letters. - 2011. - Vol. 93, Is. 9. - P. 517-520, DOI 10.1134/S0021364011090116. - Cited References: 27. - This work was supported by the Presidium of the Russian Academy of Sciences (program no. 18.7); the Russian Foundation for Basic Research (project nos. 09-02-00127, 10-02-90725-mob_st); Siberian Branch, Russian Academy of Sciences (Integration Project no. N40); and the Ministry of Education and Sciences of the Russian Federation (state contract no. P891, Program "Kadry"). . - ISSN 0021-3640

РУБ Physics, Multidisciplinary
Рубрики:
QUANTUM OSCILLATIONS
SUPERCONDUCTORS
EVOLUTION
Аннотация: The results of recently developed norm-conserving cluster perturbation theory for doping dependent electronic structure of the Hubbard model are reported. We have found that the momentum distribution of the spectral weight strongly depends on the broadening value delta. At delta = 0.1t, we reproduce the angle-resolved photoemission spectroscopy data, while at delta = 0.01t we obtain two quantum phase transitions. DOI: 10.1134/S0021364011090116

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Держатели документа:
[Ovchinnikov, S. G.] Russian Acad Sci, LV Kirensky Phys Inst, Siberian Branch, Krasnoyarsk 660036, Russia
[Ovchinnikov, S. G.] Siberian Fed Univ, Krasnoyarsk 660041, Russia
[Nikolaev, S. V.] Omsk State Univ, Omsk 644077, Russia
ИФ СО РАН
Kirensky Institute of Physics, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk 660036, Russian Federation
Siberian Federal University, Krasnoyarsk 660041, Russian Federation
Omsk State University, Omsk 644077, Russian Federation

Доп.точки доступа:
Nikolaev, S. V.; Овчинников, Сергей Геннадьевич
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14.

Nikolaev, S. V.
Cluster perturbation theory in Hubbard model exactly taking into account the short-range magnetic order in 2 x 2 cluster / S. V. Nikolaev, S. G. Ovchinnikov // J. Exp. Theor. Phys. - 2010. - Vol. 111, Is. 4. - P. 635-644, DOI 10.1134/S1063776110100146. - Cited References: 23. - The authors thank V. V. Val'kov for fruitful discussions of this work. This research was supported financially by the Russian Foundation for Basic Research (project nos. 09-02-90723-mob_st and 09-02-00127) and by program no. 5.7 of the Presidium of the Russian Academy of Sciences and integration project no. 40 of the Siberian Branch and Ural Division of the Russian Academy of Sciences. . - ISSN 1063-7761

РУБ Physics, Multidisciplinary
Рубрики:
INFINITE DIMENSIONS
SYSTEMS
STATE
Кл.слова (ненормированные):
Antiferromagnetic orders -- Characteristic energy -- Cluster perturbation theories -- Coulomb repulsions -- Density of state -- Dynamic mean field theories -- Eigenvalue problem -- Exact diagonalization -- Excited levels -- Finite temperatures -- Half-filling -- Hubbard -- Metal insulator transition temperature -- Nearest neighbors -- Numerical solution -- Pseudo-gap -- Quasiparticle spectrum -- Shadow zone -- Short-range magnetic orders -- Temperature evolution -- Zero temperatures -- Antiferromagnetism -- Eigenvalues and eigenfunctions -- Fermi level -- Hubbard model -- Mean field theory -- Metal insulator boundaries -- Perturbation techniques -- Semiconductor insulator boundaries -- Statistical mechanics -- Metal insulator transition
Аннотация: The cluster perturbation theory is presented in the 2D Hubbard model constructed using X operators in the Hubbard-I approximation. The short-range magnetic order is taken into account by dividing the entire lattice into individual 2 x 2 clusters and solving the eigenvalue problem in an individual cluster using exact diagonalization taking into account all excited levels. The case of half-filling taking into account jumps between nearest neighbors is considered. As a result of numerical solution, a shadow zone is discovered in the quasiparticle spectrum. It is also found that a gap in the density of states in the quasiparticle spectrum at zero temperature exists for indefinitely small values of Coulomb repulsion parameter U and increases with this parameter. It is found that the presence of this gap in the spectrum is due to the formation of a short-range antiferromagnetic order. An analysis of the temperature evolution of the density of states shows that the metal-insulator transition occurs continuously. The existence of two characteristic energy scales at finite temperatures is demonstrated, the larger scale is associated with the formation of a pseudogap in the vicinity of the Fermi level, and the smaller scale is associated with the metal-insulator transition temperature. A peak in the density of states at the Fermi level, which is predicted in the dynamic mean field theory in the vicinity of the metal-insulator transition, is not observed.

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Держатели документа:
[Nikolaev, S. V.
Ovchinnikov, S. G.] Russian Acad Sci, Kirenskii Inst Phys, Siberian Branch, Krasnoyarsk 660036, Russia
[Nikolaev, S. V.] Dostoevsky State Univ, Omsk 644077, Russia
[Ovchinnikov, S. G.] Siberian Fed Univ, Krasnoyarsk 660041, Russia
ИФ СО РАН
Kirenskii Institute of Physics, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk 660036, Russian Federation
Dostoevsky State University, Omsk 644077, Russian Federation
Siberian Federal University, Krasnoyarsk 660041, Russian Federation

Доп.точки доступа:
Ovchinnikov, S. G.; Овчинников, Сергей Геннадьевич
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15.

Erkaev, N. V.
Hall magnetohydrodynamic effects for current sheet flapping oscillations related to the magnetic double gradient mechanism / N. V. Erkaev, V. S. Semenov, H. K. Biernat // Phys. Plasmas. - 2010. - Vol. 17, Is. 6. - Ст. 60703, DOI 10.1063/1.3439687. - Cited References: 15. - This work is supported by RFBR (Grant Nos. N 07-05-00776-a and N 09-05-91000-ANF_a), and by Program No. 16 of RAS. Additional support is due to the Austrian "Fonds zur Forderung der wissenschaftlichen Forschung" under Project No. I 193-N16 and the "Verwaltungsstelle fur Auslandsbeziehungen" of the Austrian Academy of Sciences. . - ISSN 1070-664X

РУБ Physics, Fluids & Plasmas
Рубрики:
CLUSTER OBSERVATIONS
MAGNETOTAIL
Аннотация: Hall magnetohydrodynamic model is investigated for current sheet flapping oscillations, which implies a gradient of the normal magnetic field component. For the initial undisturbed current sheet structure, the normal magnetic field component is assumed to have a weak linear variation. The profile of the electric current velocity is described by hyperbolic functions with a maximum at the center of the current sheet. In the framework of this model, eigenfrequencies are calculated as functions of the wave number for the "kink" and "sausage" flapping wave modes. Because of the Hall effects, the flapping eigenfrequency is larger for the waves propagating along the electric current, and it is smaller for the opposite wave propagation with respect to the current. The asymmetry of the flapping wave propagation, caused by Hall effects, is pronounced stronger for thinner current sheets. This is due to the Doppler effect related to the electric current velocity. (C) 2010 American Institute of Physics. [doi:10.1063/1.3439687]

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Держатели документа:
[Erkaev, N. V.] SB RAS, Inst Computat Modelling, Krasnoyarsk, Russia
[Erkaev, N. V.] Siberian Fed Univ, Krasnoyarsk, Russia
[Semenov, V. S.] St Petersburg State Univ, Inst Phys, St Petersburg, Russia
[Biernat, H. K.] Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria
[Biernat, H. K.] Graz Univ, Inst Phys, Graz, Austria
ИВМ СО РАН

Доп.точки доступа:
Semenov, V. S.; Biernat, H. K.; Еркаев, Николай Васильевич
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16.

Aplesnin, S. S.
Simulation of magnetic properties of the two-dimensional magnetic with anisotropic antiferromagnetic interactions and cluster ordering by quantum Monte Carlo / S. S. Aplesnin, G. . Petrakovskii, N. I. Miroshnichenko // Phys. Lett. A. - 2008. - Vol. 372, Is. 26. - P. 4722-4725, DOI 10.1016/j.physleta.2008.05.010. - Cited References: 12 . - ISSN 0375-9601

РУБ Physics, Multidisciplinary
Рубрики:
SPIN SYSTEM
   EXCITATIONS
   CU3B2O6
   MODEL
Кл.слова (ненормированные):
anisotropic antiferromagnetic -- cluster ordering -- plateau of magnetization -- modulated structure -- exchange in Cu3B2O6 -- Anisotropic antiferromagnetic -- Cluster ordering -- Exchange in Cu3B2O6 -- Modulated structure -- Plateau of magnetization
Аннотация: Magnetic with anisotropic anti ferromagnetic exchange interactions and special topology of coupling in the square lattice with spins pairs ordering is studied by quantum Monte Carlo method. The antiferromagnetic order is found to be more stable as compared to spin liquid state. Exchange interactions and wave vector of structure modulation for Cu3B2O6 is estimated. Neel temperature versus strength of exchange in spin pair is calculated. Plateau and modulation of magnetic structure in field magnetization dependence is revealed. (C) 2008 Elsevier B.V. All rights reserved.

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Держатели документа:
[Aplesnin, S. S.
Petrakovskii, G.] SB RAS, Inst Phys, Krasnoyarsk 660036, Russia
[Aplesnin, S. S.
Miroshnichenko, N. I.] MF Reshetneva Aircosm Siberian State Univ, Krasnoyarsk 660014, Russia
ИФ СО РАН
M.F. Reshetneva Aircosmic Siberian State University, Krasnoyarsk, 660014, Russian Federation
Institute of Physics, SB RAS, Krasnoyarsk, 660036, Russian Federation

Доп.точки доступа:
Petrakovskii, G. A.; Петраковский, Герман Антонович; Miroshnichenko, N. I.; Аплеснин, Сергей Степанович
}
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17.

Erkaev, N. V.
Magnetic double-gradient instability and flapping waves in a current sheet / N. V. Erkaev, V. S. Semenov, H. K. Biernat // Phys. Rev. Lett. - 2007. - Vol. 99, Is. 23. - Ст. 235003, DOI 10.1103/PhysRevLett.99.235003. - Cited References: 10 . - ISSN 0031-9007

РУБ Physics, Multidisciplinary
Рубрики:
MAGNETOTAIL CURRENT SHEET
CLUSTER
Кл.слова (ненормированные):
Magnetic fields -- Magnetic properties -- Magnetohydrodynamics -- Velocity measurement -- Current sheets -- Flapping waves -- Magnetic gradients -- Stable regions -- Electromagnetic waves
Аннотация: A new kind of magnetohydrodynamic instability and waves are analyzed for a current sheet in the presence of a small normal magnetic field component varying along the sheet. These waves and instability are related to the existence of two gradients of the tangential (B(tau)) and normal (B(n)) magnetic field components along the normal (del(n)B(tau)) and tangential (del(tau)B(n)) directions with respect to the current sheet. The current sheet can be stable or unstable if the multiplication of two magnetic gradients is positive or negative. In the stable region, the kinklike wave mode is interpreted as so-called flapping waves observed in Earth's magnetotail current sheet. The kink wave group velocity estimated for the Earth's current sheet is of the order of a few tens of kilometers per second. This is in good agreement with the observations of the flapping motions of the magnetotail current sheet.

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Держатели документа:
Russian Acad Sci, Inst Computat Modelling, Krasnoyarsk, Russia
Siberian Fed Univ, Krasnoyarsk, Russia
St Petersburg State Univ, Inst Phys, St Petersburg, Russia
Austrian Acad Sci, Space Res Inst, A-8010 Graz, Austria
Graz Univ, Inst Phys, Graz, Austria
ИВМ СО РАН
Institute of Computational Modelling, Russian Academy of Sciences, Krasnoyarsk, Russian Federation
Siberian Federal University, Krasnoyarsk, Russian Federation
Institute of Physics, State University of St. Petersburg, St. Petersburg, Russian Federation
Space Research Institute, Austrian Academy of Sciences, Graz, Austria
Institute of Physics, University of Graz, Graz, Austria

Доп.точки доступа:
Semenov, V. S.; Biernat, H. K.; Еркаев, Николай Васильевич
}
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18.

Gorban, A.
Codon usage trajectories and 7-cluster structure of 143 complete bacterial genornic sequences / A. . Gorban, T. . Popova, A. . Zinovyev // Physica A. - 2005. - Vol. 353. - P. 365-387, DOI 10.1016/j.physa.2005.01.043. - Cited References: 46 . - ISSN 0378-4371

РУБ Physics, Multidisciplinary
Рубрики:
DNA-BASE COMPOSITION
   ASYMMETRIC SUBSTITUTION PATTERNS
   PROTEIN-CODING REGIONS
   MICROBIAL GENOMES
   GENE IDENTIFICATION
   MARKOV-MODELS
   G+C CONTENT
   BIAS
   PREDICTION
   SELECTION
Кл.слова (ненормированные):
genome -- cluster -- codon usage -- correlations -- entropy -- mean field -- Cluster -- Codon usage -- Correlations -- Entropy -- Genome -- Mean field -- Approximation theory -- Correlation methods -- Database systems -- Entropy -- Functions -- Genes -- Mathematical models -- Clusters -- Codon usage -- Genomes -- Mean field -- Bacteria
Аннотация: Three results are presented. First, we prove the existence of a universal 7-cluster structure in all 143 completely sequenced bacterial genomes available in Genbank in August 2004, and explained its properties. The 7-cluster structure is responsible for the main part of sequence heterogeneity in bacterial genomes. In this sense, our 7 clusters is the basic model of bacterial genome sequence. We demonstrated that there are four basic "pure" types of this model, observed in nature: "parallel triangles", "perpendicular triangles", degenerated case and the flower-like type. Second, we answered the question: how big are the position-specific information and the contribution connected with correlations between nucleotide. The accuracy of the mean-field (context-free) approximation is estimated for bacterial genomes. We show that codon us-age of bacterial genomes is a multi-linear function of their genomic G+C-content with high accuracy (more precisely, by two similar functions, one for eubacterial genomes and the other one for archaea). Description of these two codon-usage trajectories is the third result. All 143 cluster animated 3D-scatters are collected in a database and is made available on our web-site: http://www.ihes.fr/similar to zinovyev/7clusters. (c) 2005 Elsevier B.V. All rights reserved.

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Держатели документа:
Univ Leicester, Dept Math, Leicester LE1 7RH, Leics, England
RAS, SB, Inst Computat Modelling, Krasnoyarsk, Russia
Bures Sur Yvette & Bioinformat Serv Inst Curie, Inst Hautes Etudes Sci, Paris, France
ИВМ СО РАН
Department of Mathematics, University of Leicester, Leicester, University Road, Leicester LE1 7RH, United Kingdom
Institute of Computational Modelling, SB RAS, Krasnoyarsk, Russian Federation
Institut des Hautes Etudes Scientifiques, Bures-sur-Yvette and Bioinformatics Service of Institut Curie, Paris, France

Доп.точки доступа:
Popova, T.; Zinovyev, A.
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19.

Cluster embedding in an elastic polarizable environment: Density functional study of Pd atoms adsorbed at oxygen vacancies of MgO(001) / V. A. Nasluzov [et al.] // J. Chem. Phys. - 2001. - Vol. 115, Is. 17. - P. 8157-8171, DOI 10.1063/1.1407001. - Cited References: 88 . - ISSN 0021-9606

РУБ Physics, Atomic, Molecular & Chemical
Рубрики:
TRANSITION-METAL ATOMS
   AB-INITIO
   OXIDE SURFACES
   ELECTRONIC-PROPERTIES
   ENERGY CALCULATIONS
   MOLECULAR-DYNAMICS
   MOTT-LITTLETON
   MADELUNG FIELD
   IONIC-CRYSTAL
   MGO
Кл.слова (ненормированные):
Atoms -- Binding energy -- Computer simulation -- Electron energy levels -- Electronic structure -- Magnesia -- Oxygen -- Palladium -- Polarization -- Probability density function -- Quantum theory -- Relaxation processes -- Charged defects -- Cluster embedding -- Elastic polarizable environment -- Electron affinity -- Oxygen vacancies -- Adsorption
Аннотация: Adsorption complexes of palladium atoms on F-s, F-s(+), F-s(2+), and O2- centers of MgO(001) surface have been investigated with a gradient-corrected (Becke-Perdew) density functional method applied to embedded cluster models. This study presents the first application of a self-consistent hybrid quantum mechanical/molecular mechanical embedding approach where the defect-induced distortions are treated variationally and the environment is allowed to react on perturbations of a reference configuration describing the regular surface. The cluster models are embedded in an elastic polarizable environment which is described at the atomistic level using a shell model treatment of ionic polarizabilities. The frontier region that separates the quantum mechanical cluster and the classical environment is represented by pseudopotential centers without basis functions. Accounting in this way for the relaxation of the electronic structure of the adsorption complex results in energy corrections of 1.9 and 5.3 eV for electron affinities of the charged defects F-s(+) and F-s(2+), respectively, as compared to models with a bulk-terminated geometry. The relaxation increases the stability of the adsorption complex Pd/F-s by 0.4 eV and decreases the stability of the complex Pd/F-s(2+) by 1.0 eV, but it only weakly affects the binding energy of Pd/F-s(+). The calculations provide no indication that the metal species is oxidized, not even for the most electron deficient complex Pd/F-s(2+). The binding energy of the complex Pd/O2- is calculated at -1.4 eV, that of the complex Pd/F-s(2+) at -1.3 eV. The complexes Pd/F-s and Pd/F-s(+) exhibit notably higher binding energies, -2.5 and -4.0 eV, respectively; in these complexes, a covalent polar adsorption bond is formed, accompanied by donation of electronic density to the Pd 5s orbital. (C) 2001 American Institute of Physics.

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Держатели документа:
Russian Acad Sci, Inst Chem & Chem Technol, Krasnoyarsk 660049, Russia
Tech Univ Munich, Inst Phys & Theoret Chem, D-85747 Garching, Germany
Kemerovo State Univ, Dept Phys, Kemerovo 650043, Russia
ИХХТ СО РАН
Institute of Chemistry and Chemical Technology, Russian Academy of Sciences, 660049 Krasnoyarsk, Russian Federation
Institut fur Physikalische und Theoretische Chemie, Technische Universitat Munchen, 85747 Garching, Germany

Доп.точки доступа:
Nasluzov, V. A.; Rivanenkov, V. V.; Gordienko, A. B.; Neyman, K. M.; Birkenheuer, U.; Rosch, N.
}
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20.

Cluster structure and superlattices in Co and Fe films / S. M. Zharkov [et al.] // JETP Letters. - 1997. - Vol. 65, Is. 12. - P. 915-918, DOI 10.1134/1.567449. - Cited References: 9 . - ISSN 0021-3640

РУБ Physics, Multidisciplinary

Аннотация: The process of dendritic crystallization of Co and Fe films is investigated. Electron-diffraction methods show that fractal growth of dendrites in Co and Fe films proceeds by multiple twinning of the elements of a nanostructure consisting of different clusters with close-packing. The formation of superstructures is explained by a shell model of a cluster structure forming nanocrystallites. (C) 1997 American Institute of Physics.

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Держатели документа:
L. V. Kirenskii Institute of Physics, Siberian Branch, Russian Academy of Sciences, 660036 Krasnoyarsk, Russian Federation

Доп.точки доступа:
Zharkov, S. M.; Жарков, Сергей Михайлович; Zhigalov, V. S.; Жигалов, Виктор Степанович; Kveglis, L. I.; Lisitsa, Y. V.; Renskaya, K. V.; Frolov, G. I.; Фролов, Георгий Иванович
}
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