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1.
M. Pudlak R. Pincak 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(4):565-576
The electronic spectra for double-wall zigzag and armchair
nanotubes are found. The influence of nanotube curvatures on the
electronic spectra is also calculated. Our finding that the outer
shell is hole doped by the inner shell is in the difference
between Fermi levels of individual shells which originate from the
different hybridization of π orbital. The shift and rotation
of the inner nanotube with respect to the outer nanotube are
investigated. We found stable semimetal characteristics of the
armchair DWNTs in regard of the shift and rotation of the inner
nanotube. We predict the shift of kF towards the bigger wave
vectors with decreasing of the radius of the armchair nanotube. 相似文献
2.
Y. Jia G. Yu J. Dong 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(4):433-439
The binding energies and sizes of excitons, and energy splitting of
the bright-dark excitons in single-walled carbon nanotubes have been
calculated using the nonorthogonal tight-binding model, supplemented
by the long-range Coulomb interaction. It is found that the binding
energies and the sizes of excitons not only depend on tube's
diameter d, but also its chirality. However, the splitting of the
bright-dark excitons mostly depends on 1/d2. Our obtained
results show that the curvature effect is very important for the
exciton excitations in the SWNTs, especially in the smaller diameter
ones. 相似文献
3.
Hong-Kang Zhao 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(3):365-372
The ac Stark effect is investigated in the toroidal carbon nanotube system threaded with an ac magnetic flux. The Floquet
theory is employed to deal with the time-dependent quantum problems. The time-averaged energy of the system is derived and
is found to exhibit a strong relationship with an external field, and the modified energy gap has been presented. The ac flux
enhances energy gaps to cause metal-semiconductor transition. The steady current has been obtained by employing the free energy
approach, and the persistent current is a special case as the magnitude of the ac flux approaches zero. The photon-assisted
current is quite different from the persistent current due to the absorption and emission of photons. The local density of
states is obtained by calculating the Green's function in the Floquet state, and photon-resonant structures are observed.
All of the novel features are associated with the ac Stark effect, which is caused by the modification of energy levels.
Received 20 November 2002 / Received in final form 7 February 2003 Published online 20 June 2003
RID="a"
ID="a"e-mail: zhaohonk@yahoo.com 相似文献
4.
T. S. Li C. H. Lee M. F. Lin 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(1):45-50
The transport properties of finite length double-walled carbon nanotubes subject to the influences of
a transverse electric field and a magnetic field with varying polar angles
are investigated theoretically. The electrical conductance, thermal conductance and Peltier coefficient
dependences on the external fields and symmetric configuration are studied in linear response regime.
Prominent peak structures of the electrical conductance are predicted when varying the electric field strength.
The features of the
conductance peaks are found to be strongly dependent on the external fields and
the intertube interactions.
The heights of the electrical and thermal conductance peaks display the quantized behavior,
while those of the Peltier coefficient do not. The conductance peaks are found to be broadened
by the finite temperature. 相似文献
5.
A. Md. Asaduzzaman M. Springborg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):213-216
Using a parameterized density-functional tight-binding method we have calculated the electronic and structural properties
of Ge–Si nanoparticles. Starting with a spherical part of a zinc-blende/diamond crystal (with the center of the sphere at
the mid-point of a nearest-neighbour bond) we have constructed initial structures that subsequently were allowed to relax.
Structures consisting solely of Ge atoms or solely of Si atoms were studied, together with core-shell structures for which
one semiconductor forms a shell on the core of the other semiconductor. Moreover, homogeneous, ordered SiGe structures as
well as structures with a semisphere of one semiconductor and a semisphere of the other were also considered.
In analysing the results special emphasis is put on identifying particularly stable structures, on explaining the occurrence
of those, on the spatial distribution of the frontier orbitals, and on the variation of the total energy with structure and
composition. 相似文献
6.
A. Srinivasan M. N. Huda A. K. Ray 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(2):227-236
Fullerene-like silicon nanostructures with twenty and twenty-four carbon
atoms on the surface of the Si60 cage by substitution, as well as
inside the cage at various orientations have been studied within the
generalized gradient approximation to density functional theory. Full
geometry optimizations have been performed without any symmetry constraints
using the Gaussian 03 suite of programs and the LANL2DZ basis set. Thus, for the
silicon atom, the Hay-Wadt pseudopotential with the associated basis set is
used for the core electrons and the valence electrons, respectively. For the
carbon atom, the Dunning/Huzinaga double zeta basis set is employed.
Electronic and geometric properties of these nanostructures are presented
and discussed in detail. Optimized silicon-carbon fullerene like
nanostructures are found to have increased stability compared to the bare
Si60 cage and the stability depends on the number and the orientation
of carbon atoms, as well as on the nature of silicon-carbon and
carbon-carbon bonding. 相似文献
7.
M. Imamura T. Miyashita A. Tanaka H. Yasuda Y. Negishi T. Tsukuda 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):233-236
We have carried out optical and X-ray photoemission
studies of the dendrimer-encapsulated Au nanoclusters. The
dendrimer-encapsulated Au nanoclusters are prepared by the chemical
reduction of Au ions loaded within the dendrimer templates.
Photoluminescence spectrum of the dendrimer-encapsulated Au nanoclusters with
diameter of about 1.0 nm shows the visible luminescence centered at about
2.8 eV. In addition, we have measured the nanocluster-size dependent
photoemission spectra in the valence-band region. From line shape analysis
of Au 4f X-ray photoemission spectra, Au 4f core-level spectra of
the dendrimer-encapsulated Au nanoclusters reflect the size dependent
chemical-states. From these results, we discuss electronic structures and
chemical states of the dendrimer-encapsulated Au nanoclusters. 相似文献
8.
D. V. Kolesnikov V. A. Osipov 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(4):465-470
The low-energy electronic structure of icosahedral
fullerenes is studied within the field-theory model. In the field
model, the pentagonal rings in the fullerene are simulated by two
kinds of gauge fields. The first one, non-abelian field, follows
from so-called K spin rotation invariance for the spinor field
while the second one describes the elastic flow due to pentagonal
apical disclinations. For fullerene molecule, these fluxes are
taken into account by introducing an effective field due to
magnetic monopole placed at the center of a sphere.
Additionally, the spherical geometry of the
fullerene is incorporated via the spin connection term. The exact
analytical solution of the problem (both for the eigenfunctions
and the energy spectrum) is found. 相似文献
9.
M. Yamada H. Nishihara 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):257-260
Biferrocene-modified gold nanoparticles
(Aun-BFc) comprising 1.7, 2.2 and 2.9 nm
in average core diameter, d,
were synthesized by a substitution reaction of octyl
thiolate-covered nanoparticles with biferrocene-terminated
alkanethiol, 1-(9-thiononyl-1-one)-1, 1-biferrocene (BFcS).
All sizes of Aun-BFc undergo two-step
oxidation reactions in 0.1 mol dm-3
Bu4NClO4-CH2Cl2
and consecutive potential scans including the second oxidation
process lead to the formation of an adhesive redox-active gold
nanoparticle film on an electrode. The thickness of the
Aun-BFc film is controllable by the
number of potential scans. The scanning tunneling microscope
images reveal that the Aun-BFc (d = 2.9 nm) film forms many domains of
the assembled Aun-BFcs, especially the
particles are isotropically assembled in line. 相似文献
10.
I. Vilfan 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(2):277-284
The properties of
nanowires were investigated with
ab initio calculations based on the density-functional theory.
The molecules build weakly coupled one-dimensional chains, like
and Mo6S9-xIx, and the crystals are
strongly uniaxial in their mechanical and electronic properties.
The calculated moduli of elasticity and resilience along the chain axis are
c11 = 320 GPa and ER = 0.53 GPa, respectively.
The electronic band structure and optical conductivity indicate
that the
crystals are good quasi-one-dimensional conductors.
The frequency-dependent complex dielectric tensor ε, calculated
in the random-phase approximation, shows a strong Drude peak in
ε∥, i.e., for the electric field polarised parallel to
the chain axis, and several peaks related to interband transitions.
The electron energy loss spectrum is weakly anisotropic and has a strong peak
at the plasma frequency ħωp ≈20 eV.
The stability analysis shows that
is metastable against the
formation of the layered
. 相似文献
11.
Y. P. Chen Y. E. Xie X. H. Yan 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(3):333-338
We have studied the transmission resonances for a confined array of
antidots, using the lattice Green's function method. Two kinds of resonant
peaks via quasibound states are found. One kind of resonant peak corresponds
to the split quasibound states. The split states originate from the
superposition of quasibound states respectively localized in different (T or
crossed) junctions, while the number of quasibound states in each junction
is associated with the arm-width of the junction. Electrons in these split
states are mainly localized in the junctions. The other kind of resonant
peaks correspond to the high quasibound states which exist in (transverse
and longitude) multi-period confined arrays of antidots. It is interesting
to note that electrons in some of the high quasibound states are mainly
localized in the intersection of the junctions rather than in the junctions
themselves. 相似文献
12.
E. S. Dy H. Kasai 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):241-245
We study the interaction between tin(II) porphyrin (SnPor) with platinum and
non-precious Group 8B metals (iron, cobalt and nickel) by density functional
theory and discuss the electronic properties of the resulting products. We
also model the interaction of the resulting compounds with water where
applicable. Our studies indicate that, SnPor-Ni possesses electronic
properties similar to SnPor-Pt, suggesting that it may possess similar
photocatalytic properties for reduction reactions, such as converting water
to hydrogen gas. 相似文献
13.
P. Khongpracha M. Probst J. Limtrakul 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(2):211-219
The interactions of a gold atom with: (a) a single-wall carbon nanohorn
(SWNH) conic tip; (b) with a single-wall carbon nanotube (SWNT) tip; and (c)
their complexes with a CO molecule were studied using first-principle
calculations based on density functional theory. The analysis of the
pyramidalization angle (θp) as well as the π-orbital
misalignment angles indicate that there should be many reactive carbon sites
on the tips of SWNH and SWNT. It was found that SWNH provides reactive sites
that can more selectively interact with the target atom. We identified five
sites on both the SWNT tip and the nanohorn where attachment of a gold atom
leads to a stable complex. This metal is found to be bi-coordinated with the
tip of SWNH, while it is mono-coordinated with the SWNT tip. The largest
interaction energies are –10.75 kcal/mol and –16.17 kcal/mol, respectively.
The CO probe molecule binds to Au on the Au/SWNH or Au/SWNT tips with
interaction energies of –22.34 and –18.29 kcal/mol, respectively. The main
contributions of the interaction with both carbon nanostructures stems from
σ-donation and π-backbonding. The results suggest that SWNHs
could be one of the promising candidates for the development of
high-specifity nanosensors. 相似文献
14.
N. Safta A. Sakly H. Mejri M. A. Zaïdi 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(1):35-38
In this paper, we present a theoretical study of the quantized electronic states in Cd1-xZnxS quantum dots. The shape of the confining
potential, the subband energies and their eigen envelope wave functions are
calculated by solving a one-dimensional Schr?dinger equation.
Electrons and holes are assumed to be confined in dots having a flattened
cylindrical geometry with a finite barrier height at the boundary. Optical
absorption measurements are used to fit the bandgap edge of the
Cd1-xZnxS nanocrystals. An analysis of the electron band
parameters has been made as a function of Zn composition. Two main features
were revealed: (i) a multiplicity in Cd1-xZnxS quantum dots with
different crystalline sizes has been found to fit accurately experimental
data in the composition range 0 ≤x ≤0.2; (ii) the fit did not,
however, show a multiplicity for x higher than 0.4. On the other hand, we
have calculated the energy level structure of coupled Cd1-xZnxS
semiconductor quantum dots using the tight-binding approximation. As is
found the Zn composition x = 0.4 is expected to be the most favorable to
give rise a superlattice behavior for the Cd1-xZnxS quantum dots
studied. 相似文献
15.
N. Safta A. Sakly H. Mejri Y. Bouazra 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(1):75-78
We report a numerical simulation of the conduction and valence band edges of
Cd1-xZnxS nanocrystallites using a one — dimensional potential
model. Electron — hole pairs are assumed to be confined in nanospheres of
finite barrier heights. Optical absorption measurements are used to fit the
bandgap of the Cd1-xZnxS nanocrystal material. A theoretical
analysis is also made to calculate the energy location of bound excitons and
the oscillator strength of interband transitions as a function of zinc
composition. The aim of the latter study is to investigate the optical
behavior of Cd1-xZnxS nanocrystals. An attempt to explain all the
results is presented. 相似文献
16.
T. Kodaira S. Inoue Y. Murakami 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):267-270
Arrayed cationic K clusters including one 4s-electron in each cluster, i.e., Km+1
m+, were incorporated into α-cages of zeolite LTA with Si/Al=1.5. Although no magnetic phase transition was observed regarding
the temperature (T) dependence of magnetic susceptibilities originating from the 4s-electron spins (χspin) between 2 and 300 K, the χspin-T curve could be fitted by the sum of magnetic susceptibilities based on the Curie-Weiss law and Pauli paramagnetism. A possible
explanation of this behavior is the existence of a narrow energy band formed out of 1s-cluster orbitals of arrayed K clusters,
and the existence of a finite density of state at the Fermi energy. 相似文献
17.
M. Tchaplyguine S. Peredkov A. Rosso J. Schulz G. Öhrwall M. Lundwall T. Rander A. Lindblad H. Bergersen W. Pokapanich S. Svensson S. L. Sorensen N. Mårtensson O. Björneholm 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):295-299
Synchrotron-based X-ray photoelectron spectroscopy on copper and silver
cluster beams created by a magnetron-based gas-aggregation source has
allowed mapping the electron density of states (DOS) of free metallic
nanoparticles. The cluster DOS profiles obtained in the experiments strongly
resemble the infinite solid DOS shapes, but the extracted cluster
work-functions are lower than those for the bulk metal. The latter
observation is explained by the initial negative charge on most of the
clusters, created by the source. 相似文献
18.
H. Shiroishi T. Oda H. Sakashita N. Fujima 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):129-132
We have studied the electronic structure of the carbon nanotubes which
include Fe atomic wire with using the density functional theory.
As the stable geometries, we obtained the straight and zigzag wires,
which have ferromagnetic and antiferromagnetic alignments, respectively.
The antiferromagnets consists of the two ferromagnetic dimers which
couple in antiparallel alignment.
We presents the band dispersions and the density of states for the
magnetic nanotubes.
The electronic structure at the Fermi level consists of the
Fe 3d and C 2pπ states, which shows a strong hybridization
between them. 相似文献
19.
E. Perfetto G. Stefanucci M. Cini 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(2):139-142
We show that different non-conventional superconductors have one fundamental feature in common: pair eigenstates of the Hamiltonian
are repulsion-free, the W = 0 pairs. In extended Hubbard models, pairing can occur for reasonable parameter values. For (N, N) nanotubes the binding energy of the pair depends strongly on the filling and decreases towards a reduced but nonzero value
for the graphite sheet N → ∞.
Received 13 July 2002 Published online 29 November 2002 相似文献
20.
L. Kronik R. Fromherz E. Ko G. Ganteför J. R. Chelikowsky 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):33-36
We compare experimentally measured and
ab initio computed
photoelectron spectra of negatively charged deuterated silicon
clusters (
, 4m10, 0n2) produced in a plasma environment.
Based on this comparison, we discuss the kinetics and
thermodynamics of the cluster formation and the effect of
deuterium on the geometrical and electronic structure of the
clusters. 相似文献