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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : ZEIN N. E., ZINENKO V. I., FEDOROV A. S.
Заглавие : ABINITIO CALCULATIONS OF PHONON FREQUENCIES AND DIELECTRIC-CONSTANTS IN A(4)B(6) COMPOUNDS
Место публикации : Phys. Lett. A: ELSEVIER SCIENCE BV, 1992. - Vol. 164, Is. 1. - P115-119. - ISSN 0375-9601, DOI 10.1016/0375-9601(92)90916-A
Примечания : Cited References: 20
Предметные рубрики: IV-VI COMPOUNDS
CRYSTAL-STRUCTURE
Аннотация: The transverse and longitudinal optical frequencies at q = 0, the dielectric constant and the effective charges are calculated for the A4B6 type family of the semiconducting compounds GeTe, SnTe and PdTe. The calculations are performed in the framework of the density functional method with the use of the norm-conserving "first-principles" pseudopotentials. The estimated ferroelectric phase transition temperatures and a number of other calculated quantities turned out to be in good agreement with the experimental data. The variations of the electronic structure in the row PbTe-GeTe, which promote the ferroelectric phase transition for GeTe, are discussed.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : OVCHINNIKOV S.G.
Заглавие : THE INFLUENCE OF THE ANTIFERROMAGNETISM ON THE ELECTRONIC-STRUCTURE OF LA2CUO4
Разночтения заглавия :авие SCOPUS: The influence of the antiferromagnetism on the electronic structure of La2CuO4
Место публикации : J. Supercond.: PLENUM PUBL CORP, 1995. - Vol. 8: University-of-Miami Workshop on High-Temperature Superconductivity - Physical Properties and Mechanisms (JAN 05-11, 1995, CORAL GABLES, FL), Is. 5. - P675-676. - ISSN 0896-1107, DOI 10.1007/BF00727473
Примечания : Cited References: 15
Предметные рубрики: OXIDES
MODEL
Ключевые слова (''Своб.индексиров.''): electron correlations--electron structure--spin fluctuations--electron correlations--electron structure--spin fluctuations--antiferromagnetism--band structure--calculations--correlation theory--electrons--lanthanum compounds--paramagnetism--perturbation techniques--antiferromagnetic phase--electron correlations--intercluster interactions--spin fluctuations--electronic structure
Аннотация: The quasiparticle approach for electronic structure calculations considering strong electron correlations is given. The exact diagonalization of a multiband Hubbard Hamiltonian for a small cluster is combined with perturbation theory for intercluster hopping. The band structure of paramagnetic and antiferromagnetic La2CuO4 are discussed.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shabanov V. F., Korshunov M. A.
Заглавие : Manifestation of vacancies in spectra of low frequencies and the calculations of migration energy in paradichlorobenzene and paradichlorobenzene at different temperatures
Место публикации : Fiz. Tverd. Tela: MEZHDUNARODNAYA KNIGA, 1995. - Vol. 37, Is. 11. - P.3463-3469. - ISSN 0367-3294
Примечания : Cited References: 13
Предметные рубрики: CRYSTAL
ALPHA
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fedorov A. S.
Заглавие : Employment of curvilinear coordinates in ab initio calculations of insulators using pseudopotentials
Место публикации : Phys. Solid State: AMER INST PHYSICS, 1999. - Vol. 41, Is. 2. - P213-218. - ISSN 1063-7834, DOI 10.1134/1.1131090
Примечания : Cited References: 17
Предметные рубрики: ELECTRONIC-STRUCTURE CALCULATIONS
ALKALINE-EARTH OXIDES
HIGH-PRESSURE
FORMALISM
SOLIDS
Аннотация: The standard ab initio scheme for calculating the structure of crystals using nonlocal pseudopotentials is modified for use in curvilinear coordinates. A method for solving the Poisson equation for the Coulomb potential in a curved space in the k representation is found. It is shown in the example of calculations for crystals of insulators having an NaCl structure that the employment of a curved space permits a very significant decrease in the required size of the basis set. (C) 1999 American Institute of Physics. [S1063-7834(99)01102-8].
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lundin U., Sandalov I., Eriksson O., Johansson B.
Заглавие : Are there two types of f-electrons in Pr-metal?
Коллективы : International Conference on Strongly Correlated Electron Systems
Место публикации : Physica B. - 1999. - Vol. 259-61. - P.231-232. - ISSN 0921-4526, DOI 10.1016/S0921-4526(98)00790-X
Примечания : Cited References: 1
Предметные рубрики:
Ключевые слова (''Своб.индексиров.''): band calculations--hubbard model--f-electrons
Аннотация: We show that in order to properly describe the bonding properties of strongly correlated systems, here demonstrated for praseodymium metal, it is necessary to split the f-electron system into two parts. Using perturbation theory from the atomic limit we show that LDA-based calculations with f-electrons in the core can be considered as the limit of an infinite Hubbard U. Then, the correction to the total energy proportional to 1/U makes the upper f(2)--f(3) intra-atomic transitions (IT) important. Mixing interaction and f-f-hopping delocalize these IT and some of them become populated. These IT give an additional contribution to the cohesive energy. This gain in energy is the reason for the separation of the f-electron system into localized (with reduced spectral weight) and delocalized ones. (C) 1999 Elsevier Science B.V. All rights reserved.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Sorokin B. P., Marushyak A. N., Aleksandrov K. S.
Заглавие : Influence of non-homogeneous uniaxial pressure on the propagation of bulk acoustic waves in crystals
Коллективы : IEEE Annual frequency control symposium
Место публикации : Proc Annu IEEE Int Freq Control Symp. - 2000. - P.404-409. - ISBN 0161-6404
Ключевые слова (''Своб.индексиров.''): acoustic bulk wave devices--calculations--crystal defects--crystal symmetry--functions--pressure effects--tensors--cubic crystal--green-christoffel equation--uniaxial mechanical pressure--acoustic wave propagation
Аннотация: The development of the theory of propagation small amplitude bulk acoustic waves in crystals under the uniaxial mechanical pressure has made by taking into account the condition of non-homogeneous deformation of crystal sample. It has been shown that the path of bulk acoustic waves will be function of a kind non-homogeneous deformation. As an example the calculation for some crystal directions of cubic crystal Bi12GeO20 (23 point symmetry) has made.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Varganov S. A., Avramov P. V., Ovchinnikov S. G.
Заглавие : Ab initio calculations of endo- and exohedral C-60 fullerene complexes with Li+ ion and the endohedral C-60 fullerene complex with Li-2 dimer
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2000. - Vol. 42, Is. 2. - P388-392. - ISSN 1063-7834, DOI 10.1134/1.1131218
Примечания : Cited References: 16
Предметные рубрики: ELECTRONIC-STRUCTURE
ENERGIES
C60
Аннотация: The results of ab initio Hartree-Fock calculations of endo- and exohedral C-60 fullerene complexes with the Li+ ion and Li-2 dimer are presented. The coordination of the Li+ ion and the Li-2 dimer in the endohedral complexes and the coordination of Li+ ion in the exohedral complex of C-60 fullerene are determined by the geometry optimization using the 3-21G basis set. In the endohedral Li+C60 complex, the Li+ ion is displaced from the center of the C-60 cage to the centers of carbon hexa- and pentagons by 0.12 nm. In the Li-2 dimer encapsulated inside the C-60 cage, the distance between the lithium atoms is 0.02 nm longer than that in the free molecule. The calculated total and partial one-electron densities of states of C-60 fullerene are in good agreement with the experimental photoelectron and X-ray emission spectra. Analysis of one-electron density of states of the endohedral Li+@C-60 complex indicates an ionic bonding between the Li atoms and the C-60 fullerene. In the Li+C60 and Li+@C-60 complexes, there is a strong electrostatic interaction between the Li+ ion and the fullerene. (C) 2000 MAIK "Nauka/Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lundin U., Sandalov I., Eriksson O., Johansson B.
Заглавие : Modification of the standard model for the lanthanides
Место публикации : Solid State Commun.: PERGAMON-ELSEVIER SCIENCE LTD, 2000. - Vol. 115, Is. 1. - P7-12. - ISSN 0038-1098, DOI 10.1016/S0038-1098(00)00126-5
Примечания : Cited References: 33
Предметные рубрики: ELECTRONIC-STRUCTURE CALCULATIONS
DENSITY-FUNCTIONAL THEORY
PARTICLE BAND-STRUCTURE
AB-INITIO CALCULATIONS
FERROMAGNETIC NICKEL
COHESIVE PROPERTIES
CRYSTAL-STRUCTURE
MOTT INSULATORS
FERMION SYSTEMS
PR METAL
Ключевые слова (''Своб.индексиров.''): metals--electronic band structure--band structure--elastic moduli--kohn-sham scheme--rare earth elements
Аннотация: We show that incorporation of strong electron correlations into the Kohn-Sham scheme of band structure calculations leads to a modification of the standard model of the lanthanides and that this procedure removes the existing discrepancy between theory and experiment concerning the ground state properties. Within the picture suggested, part of the upper Hubbard f-band is occupied due to conduction band-f-mixing interaction (that is renormalized due to correlations) and this contributes to the cohesive energy of the crystal. The lower Hubbard band has zero width and describes fermionic excitations in the shell of localized f-s. Fully self-consistent calculations (with respect to both charge density and many-electron population numbers of the f-shell) of the equilibrium volume V-0 and the bulk modulus of selected lanthanides have been performed and a good agreement with experiment is obtained. (C) 2000 Elsevier Science Ltd. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Nasluzov V. A., Rivanenkov V. V., Gordienko A. B., Neyman K. M., Birkenheuer U., Rosch N.
Заглавие : Cluster embedding in an elastic polarizable environment: Density functional study of Pd atoms adsorbed at oxygen vacancies of MgO(001)
Место публикации : J. Chem. Phys.: AMER INST PHYSICS, 2001. - Vol. 115, Is. 17. - P8157-8171. - ISSN 0021-9606, DOI 10.1063/1.1407001
Примечания : Cited References: 88
Предметные рубрики: TRANSITION-METAL ATOMS
AB-INITIO
OXIDE SURFACES
ELECTRONIC-PROPERTIES
ENERGY CALCULATIONS
MOLECULAR-DYNAMICS
MOTT-LITTLETON
MADELUNG FIELD
IONIC-CRYSTAL
MGO
Ключевые слова (''Своб.индексиров.''): 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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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Churilov G. N., Fedorov A. S., Novikov P. V.
Заглавие : Fullerene C-60 formation in partially ionized carbon vapor
Разночтения заглавия :авие SCOPUS: Fullerene C60 formation in partially ionized carbon vapor
Место публикации : JETP Letters. - 2002. - Vol. 76, Is. 8. - P.522-526. - ISSN 0021-3640, DOI 10.1134/1.1533779
Примечания : Cited References: 15
Предметные рубрики: TOTAL-ENERGY CALCULATIONS
WAVE BASIS-SET
CLUSTERS
GROWTH
Аннотация: The assembling rate of a fullerene C-60 molecule has been theoretically studied as a function of electron concentration and temperature in partially ionized carbon vapor. For C-60 formation via one or two intermediate stages of cluster collisions, it has been shown that there is a region of plasma parameters (the temperature and electron concentration) in which fullerene C-60 is formed more efficiently. The C-60 formation rate versus temperature and electron concentration relationships have been found to correlate with the trends in the collision cross-section of carbon clusters as functions of these parameters. (C) 2002 MAIK "Nauka/Interperiodica".
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Maksimov E. G., Zinenko V. I., Zamkova N. G.
Заглавие : Ab initio calculations of the physical properties of ionic crystals
Место публикации : Phys. Usp.: TURPION LTD, 2004. - Vol. 47, Is. 11. - P1075-1099. - ISSN 1063-7869, DOI 10.1070/PU2004v047n11ABEH001796
Примечания : Cited References: 90
Предметные рубрики: STRUCTURAL PHASE-TRANSITION
LOCAL-FIELD CORRECTIONS
INDUCED BREATHING MODEL
ZINC-BLENDE STRUCTURE
ELECTRON-GAS THEORY
LATTICE-DYNAMICS
MICROSCOPIC CALCULATIONS
MACROSCOPIC POLARIZATION
STATISTICAL-MECHANICS
1ST-PRINCIPLES THEORY
Аннотация: First-principles calculations of the physical properties of ionic crystals are reviewed. Two markedly different approaches within the framework of the density functional theory are described. In one of them, the electron spectrum and wave functions are treated within the standard band picture based on the solution of Kohn-Sham equations. In the second approach, the total electron density of a crystal is represented as a super-position of the densities of individual ions. The problem of determining the electric polarization of a crystal is discussed for each approach. It is shown that it is the use of Bloch functions rather than the physics of the phenomenon that complicates the solution of this problem within the Kohn-Sham framework. The deformable and polarizable ion model is described in detail, and its application to calculating many properties of ionic crystals, including the lattice dynamics and structural stability of crystal phases, is discussed.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Gavrichkov V. A., Ovchinnikov S. G., Nekrasov I. A., Pchelkina Z. V., Anisimov V. I.
Заглавие : Hybrid LDA and generalized tight-binding method for electronic structure calculations of strongly correlated electron systems
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 2005. - Vol. 72, Is. 16. - Ст.165104. - ISSN 1098-0121, DOI 10.1103/PhysRevB.72.165104
Примечания : Cited References: 82
Предметные рубрики: T-J MODEL
DENSITY-FUNCTIONAL CALCULATION
NARROW ENERGY BANDS
MEAN-FIELD THEORY
COULOMB INTERACTIONS
FERMION SYSTEMS
COPPER OXIDES
SUPERCONDUCTORS
LA2-XSRXCUO4
OXYGEN
Аннотация: A hybrid scheme for the electronic structure calculations of strongly correlated electron systems is proposed. The ab initio local density approximation calculation is used to construct the Wannier functions and obtain single electron and Coulomb parameters of the multiband Hubbard-type model. In strong correlation regime the electronic structure within multiband Hubbard model is calculated by the generalized tight-binding method, which combines the exact diagonalization of the model Hamiltonian for a small cluster (unit cell) with perturbation treatment of the intercluster hopping and interactions. For undoped La2CuO4 and Nd2CuO4 this scheme results in charge transfer insulators with correct values of gaps and dispersions of bands in agreement with the angle-resolved photoemission data.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fedorov A. S., Sorokin P. B.
Заглавие : Optimization of the calculations of the electronic structure of carbon nanotubes
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2005. - Vol. 47, Is. 11. - P2196-2202. - ISSN 1063-7834, DOI 10.1134/1.2131167
Примечания : Cited References: 19
Предметные рубрики: MOLECULAR-DYNAMICS
ELASTIC PROPERTIES
TUBES
Аннотация: A method is proposed for calculating the electronic structure and physical properties (in particular, Young's modulus) of nanotubes, including single-walled carbon nanotubes. This method explicitly accounts for the periodic boundary conditions for the geometric structure of nanotubes and makes it possible to decrease considerably (by a factor of 10-10(3)) the time needed to calculate the electronic structure with minimum error. In essence, the proposed method consists in changing the geometry of the structure by partitioning nanotubes into sectors with the introduction of the appropriate boundary conditions. As a result, it becomes possible to reduce substantially the size of the unit cell of the nanotube in two dimensions, so that the number of atoms in a new unit cell of the modified nanotube is smaller than the number of atoms in the initial unit cell by a factor equal to an integral number. A decrease in the unit cell size and the corresponding decrease in the number of atoms provide a means for drastically reducing the computational time, which, in turn, substantially decreases with an increase in the degree of partition, especially for nanotubes with large diameters. The results of the calculations performed for carbon and non-carbon (boron nitride) nanotubes demonstrate that the electronic structures, densities of states, and Young's moduli determined within the proposed approach differ insignificantly from those obtained by conventional computational methods. (c) 2005 Pleiades Publishing, Inc.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Avramov P. V., Sorokin P. B., Fedorov A. S., Fedorov D. G., Maeda Y.
Заглавие : Band-gap unification of partially Si-substituted single-wall carbon nanotubes
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2006. - Vol. 74, Is. 24. - Ст.245417. - ISSN 1098-0121, DOI 10.1103/PhysRevB.74.245417
Примечания : Cited References: 72
Предметные рубрики: SILICON-CARBIDE NANOTUBES
DENSITY-FUNCTIONAL THEORY
TOTAL-ENERGY CALCULATIONS
WAVE BASIS-SET
ELECTRONIC-STRUCTURE
AB-INITIO
NANORODS
EXCITATIONS
TRANSITION
NANOWIRES
Аннотация: The atomic and electronic structure of a set of pristine single wall SiC nanotubes as well as Si-substituted carbon nanotubes and a SiC sheet was studied by the local-density approximation (LDA) plane wave band structure calculations. Consecutive substitution of carbon atoms by Si leads to a gap opening in the energetic spectrum of the metallic (8,8) SWCNT with approximately quadratic dependence of the band gap upon the Si concentration. The same substitution for the semiconductor (10,0) single wall carbon nanotubes (SWCNT) results in a band gap minimum (0.27 eV) at similar to 25% of Si concentration. In the Si concentration region of 12-18 %, both types of nanotubes have less than 0.5 eV direct band gaps at the Gamma-Gamma point. The calculation of the chiral (8,2) SWSi0.15C0.85NT system gives a similar (0.6 eV) direct band gap. The regular distribution of Si atoms in the atomic lattice is by similar to 0.1 eV/atom energetically preferable in comparison with a random distribution. Time dependent density functional theory (DFT) calculations showed that the silicon substitution sufficiently increases (roughly by one order of magnitude) the total probability of optical transitions in the near infrared region, which is caused by the opening of the direct band gap in metallic SWCNTs, the unification of the nature and energy of the band gaps of all SWCNT species, the large values of Si3p parallel to r parallel to Si3s radial integrals and participation of Si3d states in chemical bonding in both valence and conductance bands.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Ovchinnikov S. G.
Заглавие : LDA + GTB (generalized tight-binding) method for the electronic structure calculations of strongly correlated electron systems: Application for the band structure calculations of p-type cuprates
Место публикации : Physica C: Superconductivity and its Applications: Elsevier Science Publishing Company, Inc., 2007. - Т.460-462 II, №SPEC. ISS. - С. 1018-1019. - ISSN 0921-4534, DOI 10.1016/j.physc.2007.03.381
ГРНТИ : 29.01
РИНЦ,
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popova E. A., Volkov D. V., Vasiliev A. N., Demidov A. A., Kolmakova N. P., Gudim I. A., Bezmaternykh L. N., Tristan N., Skourski Y., Buchner B., Hess C., Klingeler R.
Заглавие : Magnetization and specific heat of TbFe3(BO3)(4): Experiment and crystal-field calculations
Разночтения заглавия :авие SCOPUS: Magnetization and specific heat of Tb Fe3 (B O3) 4: Experiment and crystal-field calculations
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 2007. - Vol. 75, Is. 22. - Ст.224413. - ISSN 1098-0121, DOI 10.1103/PhysRevB.75.224413
Примечания : Cited References: 22
Предметные рубрики: GDFE3(BO3)(4)
MAGNETOSTRICTION
Аннотация: We have studied the thermodynamic properties of single-crystalline TbFe3(BO3)(4). Magnetization measurements have been carried out as a function of magnetic field (up to 50 T) and temperature up to 350 K with the magnetic field both parallel and perpendicular to the trigonal c axis of the crystal. The specific heat has been measured in the temperature range 2-300 K with a magnetic field up to 9 T applied parallel to the c axis. The data indicate a structural phase transition at 192 K and antiferromagnetic spin ordering at T-N approximate to 40 K. A Schottky anomaly is present in the specific-heat data around 20 K, arising due to two low-lying energy levels of the Tb3+ ions being split by f-d coupling. Below T-N, magnetic fields parallel to the c axis drive a spin-flop phase transition, which is associated with a large magnetization jump. The highly anisotropic character of the magnetic susceptibility is ascribed mainly to the Ising-like behavior of the Tb3+ ions in the trigonal crystal field. We describe our results in the framework of a unified approach which is based on mean-field approximation and crystal-field calculations.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Ovchinnikov S. G.
Заглавие : LDA plus GTB (generalized tight-binding) method for the electronic structure calculations of strongly correlated electron systems: Application for the band structure calculations of p-type cuprates
Разночтения заглавия :авие SCOPUS: LDA + GTB (generalized tight-binding) method for the electronic structure calculations of strongly correlated electron systems: Application for the band structure calculations of p-type cuprates
Место публикации : Physica C: ELSEVIER SCIENCE BV, 2007. - Vol. 460: 8th International Conference on Materials and Mechanisms of Superconductivity and High Temperature Superconductors (JUL 09-14, 2006, Dresden, GERMANY). - P1018-1019. - ISSN 0921-4534, DOI 10.1016/j.physc.2007.03.381
Примечания : Cited References: 12
Предметные рубрики: 3-CENTER INTERACTIONS
MODEL
Ключевые слова (''Своб.индексиров.''): strongly correlated electron systems--superconductivity--p-type cuprates--spin fluctuations--fermi surface--fermi surface--p-type cuprates--spin fluctuations--strongly correlated electron systems--superconductivity--band structure--correlation methods--electronic structure--fermi surface--hubbard model--mean field theory--spin fluctuations--superconductivity--fermi velocity--hole pockets--strongly correlated electron systems--oxide superconductors
Аннотация: Mean-field theory of the non-superconducting phase of the high-T-c cuprates is formulated within the effective t-t'-t"-J model with three-site correlated hoppings. This model with the ab initio calculated parameters results from the LDA + GTB method. The static spin and kinematical correlation functions beyond Hubbard I approximation are calculated self-consistently taking into account hoppings to the first, the second, and the third neighboring sites, as well as the three-site correlated hoppings. The obtained Fermi surface evolves from hole-pockets at low-doping to large hole-type Fermi surface at higher doping concentrations. Calculated doping dependence of the nodal Fermi velocity, the effective mass and the chemical potential shift are in good agreement with experimental data. (c) 2007 Elsevier B.V. All rights reserved.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Avramov P. V., Kuzubov A. A., Fedorov A. S., Sorokin P. B., Tomilin F. N., Maeda Y.
Заглавие : Density-functional theory study of the electronic structure of thin Si/SiO2 quantum nanodots and nanowires
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 2007. - Vol. 75, Is. 20. - Ст.205427. - ISSN 1098-0121, DOI 10.1103/PhysRevB.75.205427
Примечания : Cited References: 63
Предметные рубрики: ERBIUM ION LUMINESCENCE
TOTAL-ENERGY CALCULATIONS
WAVE BASIS-SET
POROUS SILICON
OPTICAL-PROPERTIES
OXIDIZED SI
SEMICONDUCTOR NANOWIRES
PHASE-TRANSFORMATIONS
NANOCRYSTALS
CONFINEMENT
Аннотация: The atomic and electronic structures of a set of proposed pentagonal thin (1.6 nm in diameter) silicon/silica quantum nanodots (QDs) and nanowires (NWs) with narrow interface, as well as parent metastable silicon structures (1.2 nm in diameter), were studied using cluster B3LYP/6-31G(*) and periodic boundary condition (PBC) plane-wave (PW) pseudopotential (PP) local-density approximation methods. The total density of states (TDOS) of the smallest quasispherical QD (Si-85) corresponds well to the PBC PW PP LDA TDOS of the crystalline silicon. The elongated SiQDs and SiNWs demonstrate the metallic nature of the electronic structure. The surface oxidized layer opens the band gap in the TDOS of the Si/SiO2 species. The top of the valence band and the bottom of conduction band of the particles are formed by the silicon core derived states. The theoretical band gap width is determined by the length of the Si/SiO2 clusters and describes the size confinement effect in the experimental photoluminescence spectra of the silica embedded nanocrystalline silicon with high accuracy.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Pavlovskii M. S.
Заглавие : Lattice dynamics of BiFeO3: The untypical behavior of the ferroelectric instability under hydrostatic pressure
Место публикации : JETP Letters. - 2008. - Vol. 87, Is. 6. - P.288-291. - ISSN 0021-3640, DOI 10.1134/S0021364008060052
Примечания : Cited References: 15
Предметные рубрики: AB-INITIO CALCULATIONS
PEROVSKITE
Аннотация: Within a nonempirical model of an ionic crystal with the inclusion of the dipole and quadrupole ion polarizations, the lattice vibrational frequencies, high-frequency dielectric constant, Born dynamic charges, and the elasticity moduli of the BiFeO3 crystal have been calculated and their dependencies on the hydrostatic pressure in the cubic, rhombic, and rhombohedral phases have been determined. The results indicate the presence of the ferroelectric instability, which depends weakly on the pressure in all of the phases investigated. The dependence of the crystal lattice dynamics on the applied pressure for the cubic phases of BiAlO3, BaTiO3, and PbTiO3 has been calculated for comparison.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Avramov P. V., Fedorov D. G., Sorokin P. B., Chernozatonskii L. A., Ovchinnikov S. G.
Заглавие : Quantum dots embedded into silicon nanowires effectively partition electron confinement
Коллективы :
Место публикации : J. Appl. Phys.: AMER INST PHYSICS, 2008. - Vol. 104, Is. 5. - Ст.54305. - ISSN 0021-8979, DOI 10.1063/1.2973464
Примечания : Cited References: 22. - This work was, in part, partially supported by a Core Research for Evolutional Science and Technology (CREST) grant in the area of high performance computing for multi-scale and multiphysics phenomena from the Japan Science and Technology Agency (JST) as well as by the Russian Fund of Basic Researches (Grant No. 05-02-17443) (L.A.C.). One of the authors (P.V.A.) acknowledges the encouragement of Dr. Keiji Morokuma, Research Leader at Fukui Institute. The geometry of all presented structures was visualized by ChemCraft software. SUP23/SUP L.A.C. acknowledges I. V. Stankevich for help and fruitful discussions. P.B.S. is grateful to the Joint Supercomputer Center of the Russian Academy of Sciences for access to a cluster computer for quantum-chemical calculations.
Предметные рубрики: OPTICAL-PROPERTIES
POROUS SILICON
WIRES
PREDICTION
GROWTH
Ключевые слова (''Своб.индексиров.''): electric currents--electric wire--electronic states--electronic structure--nanostructured materials--nanostructures--nanowires--nonmetals--optical waveguides--plasma confinement--quantum confinement--quantum electronics--semiconducting silicon compounds--silicon--electronic state--band gaps--electron confinements--electronic-structure calculations--embedded structures--quantum confinement effect--quantum dots--semi-empirical methods--silicon nanowires--silicon quantum dots--semiconductor quantum dots
Аннотация: Motivated by the experimental discovery of branched silicon nanowires, we performed theoretical electronic structure calculations of icosahedral silicon quantum dots embedded into pentagonal silicon nanowires. Using the semiempirical method, we studied the quantum confinement effect in the fully optimized embedded structures. It was found that (a) the band gaps of the embedded structures are closely related to the linear sizes of the longest constituting part rather than to the total linear dimension and (b) the discovered atypical quantum confinement with a plateau and a maximum can be attributed to the substantial interactions of near Fermi level electronic states of the quantum dots and nanowire segments. (c) 2008 American Institute of Physics.
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