169 research outputs found
A unification of the interactions and the diffractive processes
The transition of a number of hadronic process characteristics to a certain universal regime is interpreted as an indication to the early origination of the unification regime of the interactions
Hysteresis of the contact angle of a meniscus inside a capillary with smooth, homogeneous solid walls
A theory of contact angle hysteresis of a
meniscus inside thin capillaries with smooth, homogeneous solid walls is developed in terms of surface forces (disjoining/
conjoining pressure isotherm) using a quasi-equilibrium approach. The disjoining
/conjoining pressure isotherm includes electrostatic, intermolecular, and structural components. The values of the static receding θr, advancing θa , and
equilibrium θe contact angles in thin capillaries were calculated on the basis of the shape of the disjoining/conjoining pressure isotherm. It was shown that both advancing and receding contact angles depend on the capillary radius. The suggested
mechanism of the contact angle hysteresis has a direct experimental confirmation: the process of receding is accompanied by the formation of thick β-films on the capillary walls. The effect of the transition from partial to complete wetting in thin capillaries is predicted and analyzed. This effect takes place in very thin capillaries, when the receding contact angle decreases to zero
Theoretical investigation of TbNi_{5-x}Cu_x optical properties
In this paper we present theoretical investigation of optical conductivity
for intermetallic TbNi_{5-x}Cu_x series. In the frame of LSDA+U calculations
electronic structure for x=0,1,2 and on top of that optical conductivities were
calculated. Disorder effects of Ni for Cu substitution on a level of LSDA+U
densities of states (DOS) were taken into account via averaging over all
possible Cu ion positions for given doping level x. Gradual suppression and
loosing of structure of optical conductivity at 2 eV together with simultaneous
intensity growth at 4 eV correspond to increase of Cu and decrease of Ni
content. As reported before [Knyazev et al., Optics and Spectroscopy 104, 360
(2008)] plasma frequency has non monotonic doping behaviour with maximum at
x=1. This behaviour is explained as competition between lowering of total
density of states on the Fermi level N(E_F) and growing of number of carriers.
Our theoretical results agree well with variety of recent experiments.Comment: 4 pages, 3 figure
Electronic structure, magnetic and optical properties of intermetallic compounds R2Fe17 (R=Pr,Gd)
In this paper we report comprehensive experimental and theoretical
investigation of magnetic and electronic properties of the intermetallic
compounds Pr2Fe17 and Gd2Fe17. For the first time electronic structure of these
two systems was probed by optical measurements in the spectral range of 0.22-15
micrometers. On top of that charge carriers parameters (plasma frequency and
relaxation frequency) and optical conductivity s(w) were determined.
Self-consistent spin-resolved bandstructure calculations within the
conventional LSDA+U method were performed. Theoretical interpetation of the
experimental s(w) dispersions indicates transitions between 3d and 4p states of
Fe ions to be the biggest ones. Qualitatively the line shape of the theoretical
optical conductivity coincides well with our experimental data. Calculated by
LSDA+U method magnetic moments per formula unit are found to be in good
agreement with observed experimental values of saturation magnetization.Comment: 16 pages, 5 figures, 1 tabl
Specific features of the electronic structure and spectral properties of NdNi5 - xCux compounds
The spectral properties of the intermetallic compounds NdNi5 - xCux (x = 0, 1, 2) have been studied using optical ellipsometry in the wavelength range 0.22-16 μm. It has been established that substitution of copper atoms for nickel leads to noticeable changes in the optical absorption spectra, plasma frequencies, and relaxation frequencies of conduction electrons. Spin-polarized calculations of the electronic structure of these compounds have been performed in the local spin density approximation allowing for strong electron correlations (LSDA + U method) in the 4f shell of the rare-earth ion. The calculated electron densities of states have been used to interpret the experimental dispersion curves of optical conductivity in the interband light absorption region. © 2013 Pleiades Publishing, Ltd
Optical spectroscopy and electronic structure of compounds HoNi 5-x Alx (x = 0, 1, 2)
The optical properties of the compounds HoNi5 - x Al x (x = 0, 1, 2) have been investigated using the ellipsometric method in the wavelength range from 0.22 to 16 μm. The electronic structure of these intermetallic compounds has been calculated in the local electron-spin density approximation with the correction for strong electronic interactions in the 4f shell of the holmium ions. The experimental dispersion dependences of optical conductivity in the region of interband light absorption have been interpreted based on the results of the calculation of the electron density of states. The plasma and relaxation frequencies of electrons have been determined. © 2013 Pleiades Publishing, Ltd
Ab initio exchange interactions and magnetic properties of Gd2Fe17 iron sublattice: rhombohedral vs. hexagonal phases
In the framework of the LSDA+U method electronic structure and magnetic
properties of the intermetallic compound Gd2Fe17 for both rhombohedral and
hexagonal phases have been calculated. On top of that, ab initio exchange
interaction parameters within the Fe sublattice for all present nearest and
some next nearest Fe ions have been obtained. It was found that for the first
coordination sphere direct exchange interaction is ferromagnetic. For the
second coordination sphere indirect exchange interaction is observed to be
weaker and of antiferromagnetic type. Employing the theoretical values of
exchange parameters Curie temperatures Tc of both hexagonal and rhombohedral
phases of Gd2Fe17 within Weiss mean-field theory were estimated. Obtained
values of Tc and its increase going from the hexagonal to rhombohedral crystal
structure of Gd2Fe17 agree well with experiment. Also for both structures
LSDA+U computed values of total magnetic moment coincide with experimental
ones.Comment: 20 pages, 2 figures; V2 as published in PR
Influence of aluminum impurity on the electronic structure and optical properties of the TbNi5 intermetallic compound
The electronic structure of the TbNi5 - xAlx intermetallic compounds (x = 0, 1, 2) is calculated in the local electron density approximation with the correction to strong electron correlations in 4f shell of terbium ions. Spectral properties of these compounds are measured by ellipsometry in a wavelength range of 0. 22-16 μm. Frequency dependences of optical conductivity in the region of interband optical absorption are interpreted based on the results of calculations of electron densities of states. The relaxation and plasma frequencies of conduction electrons are determined. © 2013 Pleiades Publishing, Ltd
Aggregation in colloidal suspensions and its influence on the suspension viscosity
Influence of aggregate formation on rheological properties of concentrated suspensions is discussed and reviewed. Methods of Stokesian and Brownian dynamic simulations of aggregation are discussed
and the results of simulations for both Brownian and non Brownian particles are presente
Development of Cross-Section Library for DYN3D Code
At present, SSTC NRS uses the HELIOS code for generation of few-group cross-section
libraries for WWER core calculations. There is an urgent issue of selecting the appropriate
approach to implement the cross-section library into the DYN3D code. The paper overviews the
application of approaches used by SSTC NRS, such as a multidimensional table and polynomial
dependences. The capabilities and possible extension of each approach are described with
inherent advantages and disadvantages. In addition, the model development and cross-section
preparation for the WWER-1000 radial reflector taking into account discontinuity factors are
discussed. Brief results of calculations with the use of different approaches are presented.На даний час ДНТЦ ЯРБ використовує спектральний код HELIOS для підготовки
малогрупових бібліотек нейтронно-фізичних констант тепловидільних збірок (ТВЗ)
активних зон ВВЕР. У процесі розробки моделей ТВЗ виникає актуальна проблема
вибору правильного підходу до реалізації бібліотеки констант у коді DYN3D.
У даній роботі надано результати досліджень підходів, що використовує
ДНТЦ ЯРБ, — реалізації бібліотеки у вигляді багатовимірної таблиці й
поліноміальних залежностей. Розглянуто підходи ДНТЦ ЯРБ до вирішення
проблеми розробки моделі та підготовки нейтронно-фізичних констант радіального
відбивача для ВВЕР-1000 з урахуванням факторів розривності. Наведено короткі
результати розрахункових досліджень при використанні різних підходів.В настоящее время ГНТЦ ЯРБ использует спектральный код HELIOS для
подготовки малогрупповых библиотек нейтронно-физических констант
тепловыделяющих сборок активных зон ВВЭР. В ходе разработки моделей
тепловыделяющих сборок возникает актуальная проблема выбора правильного
подхода к реализации библиотеки констант в коде DYN3D. В данной роботе
представлены результаты исследований подходов, используемых ГНТЦ ЯРБ, —
реализации библиотеки в виде многомерной таблицы и полиномиальных
зависимостей. Показаны подходы к решению проблемы разработки модели и
подготовки нейтронно-физических констант радиального отражателя для ВВЭР-
1000 с учетом факторов разрывности. Даны краткие результаты расчетных
исследований при использовании различных подходов
- …