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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bykov A. A., Terent'yev K. Yu., Gokhfeld D. M., Petrov M. I.
Заглавие : Fractal dimension of cluster boundaries in porous polycrystalline HTSC materials
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 54, Is. 10. - P.1947-1950. - ISSN 1063-7834, DOI 10.1134/S1063783412100095
Примечания : Cited References: 20
Предметные 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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ershov A. E., Isaev I. L., Semina P. N., Markel V. A., Karpov S. V.
Заглавие : Effects of size polydispersity on the extinction spectra of colloidal nanoparticle aggregates
Место публикации : Phys. Rev. B: American Physical Society, 2012. - Vol. 85, Is. 4. - Ст.045421. - P. - ISSN 1098-0121, DOI 10.1103/PhysRevB.85.045421
Примечания : Cited References: 41. - This work was supported by grants from the following foundations of the Russian Federation: Presidium of RAS, OFN RAS, and SB RAS.
Предметные рубрики: METAL FRACTAL CLUSTERS
OPTICAL-PROPERTIES
ABSORPTION
NONLINEARITIES
COMPOSITES
SCATTERING
PARTICLES
SPHERES
GRAINS
Аннотация: We investigate the effect of particle polydispersity on the optical extinction spectra of colloidal aggregates of spherical metallic (silver) nanoparticles, taking into account the realistic interparticle gaps caused by layers of stabilizing polymer adsorbed on the metal surface (adlayers). The spectra of computer-generated aggregates are computed using two different methods. The coupled-multipole method is used in the quasistatic approximation and the coupled-dipole method beyond the quasistatics. The latter approach is applicable if the interparticle gaps are sufficiently wide relative to the particle radii. Simulations are performed for two different particle size distribution functions (bimodal and Gaussian), varying the number of particles per aggregate, and different distribution functions of the interparticle gap width. The strong influence of the latter factor on the spectra is demonstrated and investigated in detail.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Stan S., Balasoiu M., Cristescu C. P., Stolyar S. V., Iskhakov R. S., Raikher Yu. L.
Заглавие : 2nd Fractional Brownian motion simulation for the fractal properties of ferryhidrite nanoparticles
Коллективы : "Complex and magnetic soft matter systems: physico-mechanical properties and structure", International summer school and workshop
Место публикации : 2nd International summer school and workshop complex and magnetic soft matter systems: physico-mechanical properties and structure: books of abstacs. - 2014. - P.78-79
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Karpov S. V., Gerasimov V. S., Isaev I. L., Markel V. A.
Заглавие : Local anisotropy and giant enhancement of local electromagnetic fields in fractal aggregates of metal nanoparticles
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2005. - Vol. 72, Is. 20. - Ст.205425. - ISSN 1098-0121, DOI 10.1103/PhysRevB.72.205425
Примечания : Cited References: 56
Предметные рубрики: SMALL-PARTICLE COMPOSITES
DIFFUSION-LIMITED AGGREGATION
OPTICAL-PROPERTIES
SELECTIVE PHOTOMODIFICATION
NUMERICAL-SIMULATION
DISORDERED CLUSTERS
ABSORPTION-SPECTRUM
PARTICULATE MATTER
NONLINEAR OPTICS
LIGHT-SCATTERING
Аннотация: We have shown within quasistatic approximation that the giant fluctuations of a local electromagnetic field in random fractal aggregates of silver nanospheres are strongly correlated with a local anisotropy factor S which is defined in this paper. The latter is a purely geometrical parameter which characterizes the deviation of local environment of a given nanosphere in an aggregate from spherical symmetry. Therefore, it is possible to predict the sites with anomalously large local fields in an aggregate without explicitly solving the electromagnetic problem. We have also demonstrated that the average (over nanospheres) value of S does not depend noticeably on the fractal dimension D, except when D approaches the trivial limit D=3. In this case, as one can expect, the average local environment becomes spherically symmetrical and S approaches zero. This corresponds to the well-known fact that in trivial aggregates, fluctuations of local electromagnetic fields are much weaker than in fractal aggregates. Thus, we find that, within the quasistatics, the large-scale geometry does not have a significant impact on local electromagnetic responses in nanoaggregates in a wide range of fractal dimensions. However, this prediction is expected not to be correct in aggregates which are sufficiently large for the intermediate- and radiation-zone interaction of individual nanospheres to become important.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Markel V. A., Pustovit V. N., Karpov S. V., Obuschenko A. V., Gerasimov V. S., Isaev I. L.
Заглавие : Electromagnetic density of states and absorption of radiation by aggregates of nanospheres with multipole interactions
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2004. - Vol. 70, Is. 5. - Ст.54202. - ISSN 1098-0121, DOI 10.1103/PhysRevB.70.054202
Примечания : Cited References: 81
Предметные рубрики: DISCRETE-DIPOLE APPROXIMATION
ENHANCED RAMAN-SCATTERING
METAL FRACTAL CLUSTERS
OPTICAL-PROPERTIES
SELECTIVE PHOTOMODIFICATION
DISORDERED CLUSTERS
NUMERICAL-SIMULATION
SPECTRAL DEPENDENCE
PARTICULATE MATTER
LIGHT-SCATTERING
Ключевые слова (''Своб.индексиров.''): carbon--iron--palladium--silver--article--dipole--electromagnetic field--geometry--mathematical analysis--molecular interaction--nanoparticle--radiation absorption
Аннотация: We calculate the quasistatic electromagnetic density of states for aggregates of touching spheres, in particular, linear chains and computer-generated random fractal aggregates. Multipole moments with orders of up to L=64 are taken into account for random aggregates with the number of particles of up to N=100 and up to L=8000 for linear chains. Extensive comparisons with the dipole approximation and geometrical cluster renormalization method are performed. Extinction spectra are calculated for several metals and black carbon. Long wavelength electromagnetic properties of fractal aggregates are considered in details.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Karpov S. V., Popov A. K., Slabko V. V.
Заглавие : Photochromic reactions in silver nanocomposites with a fractal structure and their comparative characteristics
Место публикации : Tech. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2003. - Vol. 48, Is. 6. - P749-756. - ISSN 1063-7842, DOI 10.1134/1.1583830
Примечания : Cited References: 24
Предметные рубрики: SMALL-PARTICLE COMPOSITES
OPTICAL-PROPERTIES
COLLOIDAL SILVER
SELECTIVE PHOTOMODIFICATION
CLUSTERS
LIGHT
Аннотация: Conditions for a change in the polarization selectivity of dips in the plasmon absorption spectra of fractal silver nanocomposites irradiated by pulsed laser radiation are studied. The energy thresholds of the polarization selectivity are evaluated, and the polarization and spectral threshold characteristics are compared. Mechanisms behind the correlation between the fractal structure of the nanocomposites, on the one hand, and their optical and photochromic properties, on the other hand, are discussed. (C) 2003 MAIK "Nauka / Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gluck M., Kolovsky A. R., Korsch H. J.
Заглавие : Fractal stabilization of Wannier-Stark resonances
Место публикации : Europhys. Lett. - 2000. - Vol. 51, Is. 3. - P.255-260. - ISSN 0295-5075, DOI 10.1209/epl/i2000-00345-2
Примечания : Cited References: 17
Предметные рубрики: BLOCH PARTICLE
FIELDS
STATISTICS
QUANTUM
SYSTEMS
AC
DC
ELECTRONS
Аннотация: The quasienergy spectrum of a Bloch electron affected by dc-ac fields is known to have a fractal structure as a function of the so-called electric matching ratio, which is the ratio of the ac field frequency and the Bloch frequency. This paper studies a manifestation of the fractal nature of the spectrum in the system "atom in a standing laser wave", which is a quantum-optical realization of a Bloch electron. It is shown that for an appropriate choice of the system parameters the atomic survival probability (a quantity measured in laboratory experiments) also develops a fractal structure as a function of the electric matching ratio. Numerical simulations under classically chaotic scattering conditions show good agreement with theoretical predictions based on random matrix theory.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Myagkov V. G., Bykova L. E.
Заглавие : Fractal clusters and self-propagating high-temperature synthesis in thin Al/Ge films
Место публикации : JETP Letters. - 1998. - Vol. 67, Is. 5. - P.334-338. - ISSN 0021-3640, DOI 10.1134/1.567669
Примечания : Cited References: 14
Предметные рубрики: DENSE BRANCHING MORPHOLOGY
SINGLE-CRYSTAL GROWTH
AL-GE
PHASE-SEPARATION
Аннотация: Fractal clusters in amorphous thin films are examples of growth models. The main models are the Witten-Sander model and its modifications. It is believed that fractal patterns are formed in the course of the crystallization of an amorphous phase. It is shown that self-propagating high-temperature synthesis can be initiated in an Al/Ge film system and fractal patterns are formed in the reaction products. It is conjectured that the transition of an amorphous phase to a crystalline phase does not play a substantial role in the appearance of such patterns, while the formation of fractal clusters is determined by self-propagating high-temperature synthesis. (C) 1998 American Institute of Physics. [S0021-3640(98)00605-7].
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Markel V. A., Shalaev V. M., Poliakov E. Y., George T. F.
Заглавие : Numerical studies of second- and fourth-order correlation functions in cluster-cluster aggregates in application to optical scattering
Место публикации : Phys. Rev. E: AMERICAN PHYSICAL SOC, 1997. - Vol. 55, Is. 6. - P7313-7333. - ISSN 1063-651X, DOI 10.1103/PhysRevE.55.7313
Примечания : Cited References: 21
Предметные рубрики: DIFFUSION-LIMITED AGGREGATION
COLLOIDAL AGGREGATION
FRACTAL CLUSTERS
ANTICORRELATION
SIMULATIONS
Аннотация: Two- and four-point density correlation functions p(2)(r) and p(4)(r) are studied numerically and theoretically in computer-generated three-dimensional lattice cluster-cluster aggregates (CCA) with the number of particles N up to 20 000 in application to the light scattering problem. The ''pure'' aggregation algorithm is used, where subclusters of all possible sizes are allowed to collide. We find that large CCA clusters demonstrate pronounced multiscaling. In particular, the fractal dimension determined from the slope of p(2)(r) at small distances differs from that found from the dependence of the radius of gyration on the number of monomers (according to our data, 1.80 and 1.94, respectively). We also consider different functional forms for p(2) and their general properties and applicability. We find that the best fit to the numerical data is provided by the generalized exponential cutoff function with coefficients depending on N. The latter dependence is a manifestation of multiscaling. We propose some theoretical approaches for calculating p(4)(r), assuming p(2)(r) is known. In particular, we find the small-r asymptote for the p(4)(r) and verify it numerically. In addition, we find that p(4)(r) cannot be represented by a scaling dependence with a cutoff function, like p(2)(r) Instead, p(4)(r) is given by an expansion in terms of integer powers of r(2D-3), where D is the fractal dimension (approximate to 1.8 for CCA clusters).
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Karpov S. V., Gerasimov V. S., Isaev I. L., Markel V. A.
Заглавие : Spectroscopic studies of fractal aggregates of silver nanospheres undergoing local restructuring
Место публикации : J. Chem. Phys.: AMER INST PHYSICS, 2006. - Vol. 125, Is. 11. - Ст.111101. - ISSN 0021-9606, DOI 10.1063/1.2229202
Примечания : Cited References: 30
Предметные рубрики: ENHANCED RAMAN-SCATTERING
SMALL-PARTICLE COMPOSITES
OPTICAL-PROPERTIES
DISORDERED CLUSTERS
NONLINEAR OPTICS
LOCALIZATION
NANOPARTICLES
EIGENMODES
BOUNDS
Ключевые слова (''Своб.индексиров.''): large-scale fractal geometry--nonlinear optical responses--restructuring--silver nanospheres--aggregates--colloids--electromagnetic fields--fractals--nonlinear optics--sampling--spectroscopic analysis--silver
Аннотация: We present an experimental spectroscopic study of large random colloidal aggregates of silver nanoparticles undergoing local restructuring. We argue that such well-known phenomena as strong fluctuation of local electromagnetic fields, appearance of "hot spots" and enhancement of nonlinear optical responses depend on the local structure on the scales of several nanosphere diameters, rather than the large-scale fractal geometry of the sample. (c) 2006 American Institute of Physics.
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