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111.
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
112.
J.J. Liu S.F. Zhang Y.X. Li X.J. Kong 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(1):17-20
Using a two-parameter wave function, we calculate variationally the binding energy of an exciton bound to an ionized donor
impurity (D+,X) in GaAs-AlxGa1-xAs quantum wells for the values of the well width from 10 to 300 ?, when the dopant is located in the center of the well and
at the edge of the well. The theoretical results confirm that the previous experimental speculation proposed by Reynolds et al. [Phys. Rev. B 40, 6210 (1989)] is the binding energy of D+,X for the dopant at the edge of the well. In addition, we also calculate the center-of-mass wave function of the exciton and
the average interparticle distances. The results are discussed in detail.
Received 17 July 2000 and Received in final form 13 November 2000 相似文献
113.
The authors employ the method of upper and lower solutions coupled with the monotone iterative technique to obtain some results on the existence and uniqueness of the solution for anti-periodic boundary value problem of delay differential equations. 相似文献
114.
115.
Propagation characteristics of surface plasmon polaritons (SPPs) in the lamellar heterostructure, which is actually a SPP waveguide array, constructed by two kinds of single negative (SNG) material layers stacked alternatively are investigated. Based on the finite element method (FEM), the negative-refraction (NR) property is demonstrated when the electromagnetic wave penetrates through free space into such SNG lamellar structure. A clear view of the underlying physics of NR is presented qualitatively that is mainly related to the coupled SPPs. The strong coupling effect leads to the novel SPP dispersion curves and then the anomalous propagation characteristics. 相似文献
116.
C. Tang K. Deng W. Tan Y. Yuan Y. Liu J. Yang X. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):125-128
The formation mechanism, geometric structures, and
electronic properties of a metal-substituted fullerene
C58Fe2 have been studied using frontier orbital theory
(FOT) and density functional theory (DFT). FOT predicts that two
Fe atoms prefer to substitute the two carbons of a [6,6] double
bond of C60 yielding a structure denoted as C58Fe2-3, which
is different from the two equivalent substitution sites, i.e., the
sites on the opposite of C60 cage or in the nearest
neighboring sites of a pentagonal ring for C58X2 (X=N and
B), and also different from the cross sites of a hexagonal ring
for C58Si2. Five possible structures of C58Fe2 are
optimized using DFT to see whether FOT works. The DFT calculations
support the prediction of FOT. The Mulliken charge of Fe atom in
C58Fe2-3 shows that the two Fe atoms of C58Fe2-3
lose 0.70 electron to the carbons of the cage, and the net spin
populations of Fe atom indicate that each Fe atom has 1.11 μB
magnetic moments, while each of the four nearest neighboring
carbons has
magnetic moments. Thus, the two Fe
atoms have ferromagnetic interaction with each other, and have
weak antiferromagnetic interaction with their four nearest
neighboring carbons, leaving 2.0 μB magnetic moments for the
molecule. 相似文献
117.
H. M. Srivastava 《Integral Transforms and Special Functions》2017,28(7):560-564
The main purpose of this note is to draw the reader's attention towards some errors and omissions in a recent work involving solutions of some families of fractional-order differential equations, which was published in this Journal (see, for details, [Tomovski ?, Hilfer R, Srivastava HM. Fractional and operational calculus with generalized fractional derivative operators and Mittag–Leffler type functions. Integral Transforms Spec Funct. 2010;21:797–814]). Several relevant remarks and observations on some other related recent developments on this subject are also presented. 相似文献
118.
W. Zhong W. Chen H.Y. Jiang X.S. Liu C.T. Au Y.W. Du 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(3):331-337
Polycrystalline two-layered perovskite La2.5-xK0.5+xMn2O
7 + δ
(0 <
x
< 0.5) samples have been prepared by a modified sol-gel method and their magnetoresistance and magnetocaloric effects have been
studied. A large deviation between the metal-insulator (MI) transition temperature (T
ρ
) and the magnetic transition temperature (TC) is observed. Large magnetoresistance (MR) effects with Δρ/ρ
of ∼40% at 12 kOe are obtained in wide temperature ranges. The maximum of the magnetic entropy change peaks at its Curie temperature
(TC), far above its MI transition temperature (T
ρ
). The large magnetic entropy change (∼1.4 J/kg.K) is obtained in the sample La2.5-xK0.5+xMn2O
7 + δ
(x
= 0.35) upon 10 kOe applied magnetic field.
Received 2 May 2002 / Received in final form 1st October 2002 Published online 19 December 2002
RID="a"
ID="a"e-mail: wzhong@ufp.nju.edu.cn 相似文献
119.
T. Ohm C. Sangregorio C. Paulsen 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(2):195-199
We observed non-exponential relaxation for a quantum tunneling molecular magnetic system at very low temperatures and argue
that it results from evolving intermolecular dipole fields. At the very beginning of the relaxation, the magnetization follows
a square-root time dependence. A simple model is developed for the intermediate time range that is in good agreement with
the data over 4 decades in time. Detailed numerical calculations as well as measurements are presented which indicate unusual
correlation effects in these systems.
Received: 15 May 1998 / Revised: 10 July 1998 / Accepted: 11 July 1998 相似文献
120.
According to the equation of motion in the elastic medium and integral equation of target scattering, the sound scattering from the partially water-filled elastic spherical shells with and without an inner plate is studied using the finite element and boundary element method, and the scattering normalized form functions of the shell filled with different volume of water are computed and the mechanism of resonance scattering is analyzed. The results show that the resonance of the shell with partially water-filled and without the plate is mainly related to the volume of water, and the resonance is produced by inner water and the spherical shell. The resonance characteristics of partially water-filled elastic shell with the plate are similar to that of empty structured elastic spherical shell, and the sound field in inner water is weaker which indicates the main resonance characteristics are decided by spherical shell and the plate. In addition, the scattering characteristics of spherical shell with plate and one side full water-filled are greatly different from the partially water-filled ones. 相似文献