共查询到20条相似文献,搜索用时 15 毫秒
1.
B. Song Y. Yong J. Hou P. He 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,59(3):399-406
Density-functional theory with generalized gradient approximation for the exchange-correlation potential has been used to
calculate the structural and electronic properties of
Si
n
C
n
(n = 10–15) clusters. We find that the Si
n
C
n
clusters prefer cagelike structures. An extensive isomer search shows that the lowest-energy arrangements are those in which
the silicon atoms and the carbon atoms form two distinct subunits. It is found that the carbon atoms favor to form fullerene-like
structure due to the
sp
2-like bond. The silicon atoms are trying to cope with an unfavorable
sp
2 environment, but distorted tetrahedra still show up somewhere of the cagelike structures. On the basis of the lowest-energy
geometries obtained, the binding energy, HOMO–LUMO gap, Mulliken charge, ionization potential and electron affinity of the
clusters have been computed and analyzed. An electronic charge transfer from the Si-populated to the C-populated regions is
observed. 相似文献
2.
3.
The hyperfine splittings in heavy quarkonia are studied in a model-independent way using experimental data on dielectron widths.
Relativistic correlations are taken into account together with the smearing of spin-spin interaction. The radius of smearing
is fixed by known G/ψ−η
c(1S), ψ(2S)−η
c′(2S) splittings, which appears to be small, r
ss ≅ 0.06 fm. Nevertheless, even with such a small radius, substantial suppression of hyperfine splittings (∼50%) is observed
in bottomonium. For nS b
states (n = 1, 2, ..., 6), our predicted splittings (in MeV) are 28, 12, 10, 5, 6, 3. For the 3S and 4S charmonium states, the splittings 16(2) and 12(4) MeV are obtained.
The text was submitted by the authors in English. 相似文献
4.
S. P. Baranov A. V. Lipatov N. P. Zotov 《The European Physical Journal C - Particles and Fields》2011,71(4):1631
We investigate the inclusive photoproduction of J/ψ mesons at HERA within the framework of the k
T
-factorization QCD approach. Our study is based on the color singlet model supplemented with the relevant off-shell matrix
elements and the CCFM and KMR unintegrated gluon densities in a proton and in a photon. Both the direct and resolved photon
contributions are taken into account. Our predictions are compared with the recent experimental data taken by the H1 and ZEUS
collaborations. Special attention is put on the J/ψ polarization parameters λ and ν, which are sensitive to the production dynamics. 相似文献
5.
Q. L. Lu Q. Q. Luo L. L. Chen J. G. Wan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,61(2):389-396
Extensive studies of structural and magnetic properties of pure Ni
n
(n=2–21) clusters are carried out
using density functional theory with generalized gradient approximation. A new structural growth pattern is
reported and the icosahedron sequence is not the global minima structures for size n < 16. The evolution
pattern of Ni5–Ni10 clusters is based on square pyramid. For cluster between n = 9 and n = 14,
structures of them are trilayered stacking pattern. Especially for Ni13, it seriously deviates from
icosahedral pattern which was frequently assumed in previous studies. Ni10, Ni13 and Ni14 are
pieces of a double tetrahedron. For cluster size larger than 16, icosahedron based configurations are found to
be the dominative structure pattern with exception of Ni19. But trilayered structure is a strong
competitor due to small difference in energy between this pattern and icosahedral family. The comparison of
magnetic behavior between the calculations and experimental results are conducted. The average coordination
mainly dominates on the magnetic behavior in the size range we considered. 相似文献
6.
G. M. Abramova N. V. Volkov G. A. Petrakovskiĭ Y. Mita O. A. Bayukov D. A. Velikanov A. M. Vorotynov V. V. Sokolov A. F. Bovina 《JETP Letters》2007,86(6):371-374
Results of an experimental study of MnS, FeS, and Fe x Mn1?x S single crystals are presented. The phase composition, the lattice parameters, and the state of paramagnetic ions in Fe x Mn1?x S have been determined by x-ray diffraction analysis and Mössbauer spectroscopy. A sequence of transitions have been found in iron manganese sulfide with x = 0.29 at temperatures T 1 ≈ 25–50 K, T 2 ≈ 125 K, and T 3 ≈ 190 K with a change in kinetic properties and the formation of a metallic state at low temperatures T ≈ 2 K. The possibility of a Mott-Hubbard transition in Fe x Mn1?x S sulfides with variation of the composition and the temperature is discussed. 相似文献
7.
The electronic structure and ground state parameters of B2 RuAl-based refractory alloys have been investigated in the framework of the density functional theory using the exact muffin-tin
orbital method in combination with the coherent potential approximation. It has been demonstrated that the number of states
at the Fermi level for the Ru1 − x
Me
x
Al alloys as a function of the alloying metal content has a minimum, which indicates a change in the Fermi surface topology
and the presence of specific features in the behavior of elastic constants. It has been concluded that the electronic structure
of the alloys can be described in terms of the rigid band model. The nonlinear variations of the lattice parameters of the
alloys has been explained. 相似文献
8.
Bastian Kubis Sebastian P. Schneider 《The European Physical Journal C - Particles and Fields》2009,62(3):511-523
Strong final-state interactions create a pronounced cusp in η′→η
π
0
π
0 decays. We adapt and generalize the non-relativistic effective field theory framework developed for the extraction of π
π scattering lengths from K→3π decays to this case. The cusp effect is predicted to have an effect of more than 8% on the decay spectrum below the π
+
π
− threshold. 相似文献
9.
Om diagnostic is a good geometric method to differentiate one dark energy model from LCDM. We apply three different two-parameter
equation of state ω
σ
(EOS) to Dilaton Dark energy (DDE) model and investigate the Om diagnostic for these cases. We obtain that DDE model can be easily distinguished from LCDM no matter which case is considered.
We also investigate the influence of coupled parameter α on the evolutive behavior of Om−z. According to the numerical result of Om, we get the current value of equation of state ω
σ0=−0.939 which fits the observational data well. 相似文献
10.
A. V. Germanenko G. M. Minkov O. E. Rut A. A. Sherstobitov B. N. Zvonkov 《Bulletin of the Russian Academy of Sciences: Physics》2008,72(2):219-222
The temperature dependence of the conductivity of the two-dimensional hole gas in an asymmetric GaAs/In x Ga1 ? x As/GaAs quantum well has been investigated. It is shown that fast spin relaxation leads to metallic-like behavior of the temperature dependence of the conductivity. 相似文献
11.
A. K. Chaudhuri 《The European Physical Journal C - Particles and Fields》2009,61(2):331-338
In a hydrodynamic model, we have studied J/ψ production in Au+Au/Cu+Cu collisions at RHIC energy,
GeV. At the initial time, J/ψ’s are randomly distributed in the fluid. As the fluid evolves in time, the free streaming J/ψ’s are dissolved if the local fluid temperature exceeds a threshold temperature T
J/ψ
. Sequential melting of charmonium states (χ
c
, ψ
′ and J/ψ), with melting temperatures
, T
J/ψ
≈2T
c
and feed-down fraction F≈0.3, explains the PHENIX data on the centrality dependence of J/ψ suppression in Au+Au collisions. J/ψ
p
T
spectra and the nuclear modification factor in Au+Au collisions are also well explained in the model. The model however overpredicts
the centrality dependence of J/ψ suppression in Cu+Cu collisions by 20–30%. The J/ψ
p
T
spectra are underpredicted by 20–30%. The model predicts that in central Pb+Pb collisions at LHC energy,
GeV, J/ψ’s are suppressed by a factor of ∼10. The model predicted a J/ψ
p
T
distribution in Pb+Pb collisions at LHC is similar to that in Au+Au collisions at RHIC. 相似文献
12.
We establish some general theorems for the existence and nonexistence of ground state solutions of steady-state N coupled nonlinear Schrödinger equations. The sign of coupling constants β ij ’s is crucial for the existence of ground state solutions. When all β ij ’s are positive and the matrix Σ is positively definite, there exists a ground state solution which is radially symmetric. However, if all β ij ’s are negative, or one of β ij ’s is negative and the matrix Σ is positively definite, there is no ground state solution. Furthermore, we find a bound state solution which is non-radially symmetric when N=3. 相似文献
13.
A. P. Ponce-Tadeo J. L. Morán-López J. L. Ricardo-Chavez 《Journal of nanoparticle research》2016,18(11):330
An exhaustive study of the structural and magnetic properties of Fe7?n Pt n with n = 0, 1, 2, …7, bimetallic clusters is presented. Based on ab initio density functional theory that includes spin-orbit coupling (SOC) and graph theory, the ground state geometry, the local chemical order, and the orbital and spin magnetic moments are calculated. We show how the systems evolves from the 3-d Fe to the quasi-planar Pt clusters. These calculations show that SOC are necessary to describe correctly the composition dependence of the binding energy of these nanoalloys. We observe that the ground state geometries on the Fe rich side resemble the fcc structure adopted by bulk samples. Furthermore, we observe how the spin and orbital magnetic moments depend on the chemical concentration and chemical order. Based on these results, we estimated the magnetic anisotropy energy and found that the largest values correspond to some of the most symmetric structures, Fe5Pt2 and FePt6. To determine the degree of non-collinearity, we define an index that shows that in FePt6 the total magnetic moments, on each atom, are the less collinear. 相似文献
14.
The process γ*γ → σ is investigated in the framework of the SU(2)×SU(2) chiral NJL model. The form factor of the process is derived for arbitrary virtuality of γ* in the Euclidean kinematic domain. The asymptotic behavior of this form factor resembles the asymptotic behavior of the γ*γ → π form factor. 相似文献
15.
S. G. Petrosyan A. M. Khanbekyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2017,52(3):281-285
The photocurrent induced by the local excitation of the light beam focused up to 0.17 μm on the surface of a semiconductor element in the planar structure with two p–n junctions, that is, with the use of the so-called scanning laser microscopy technique, has been studied experimentally. The linear dependence of the photocurrent on the coordinate of the beam center is obtained. The high sensitivity of the structure enables to detect the displacement of the order of tens nanometers. 相似文献
16.
G. M. Abramova G. A. Petrakovskii V. V. Sokolov D. A. Velikanov A. M. Vorotynov A. F. Bovina A. A. Amirov A. M. Aliev L. N. Khanov G. S. Patrin 《Physics of the Solid State》2012,54(3):531-536
This paper reports on first results of the synthesis and study of the thermal, structural, electrical, resonance, and magnetic
properties of new sulfide materials Me
x
Mn1 − x
S (Me = Cu, 0 < x < 0.2) synthesized based on manganese monosulfide. The materials have a NaCl cubic structure at 300 K and undergo a concentration
metal-insulator transition with increasing degree of substitution and with varying temperature. The magnetic transition occurs
in the region of the heat capacity anomaly. The Néel temperature is slightly dependent on the copper concentration. The samples
with a high copper content exhibit metallic conduction at T < 260 K and semiconductor conduction at T > 260 K. 相似文献
17.
D. Arnaudon N. Crampé A. Doikou L. Frappat É. Ragoucy J. Avan 《Czechoslovak Journal of Physics》2004,54(11):1153-1158
We consider open spin chains based on osp(M2n) Yangians and solve the reflection equations for some classes of reflection matrices, including the diagonal ones. Having then integrable open spin chains, we write the analytical Bethe Ansatz equations. More details and references can be found in D. Arnaudon et al.: Nucl. Phys B 668 (2003) 469 and 687 (2004) 257. 相似文献
18.
A. Polishchuk 《Communications in Mathematical Physics》2004,247(3):527-551
The main result of this paper is the proof of the transversal part of the homological mirror symmetry conjecture for an elliptic curve that states an equivalence of two A-categories: one is built using holomorphic vector bundles on an elliptic curve and another is a subcategory in the Fukaya A-category of a torus. The proof is based on the study of A-structures on the category of line bundles over an elliptic curve satisfying some natural restrictions (in particular, m1 should be zero, m2 should coincide with the usual composition). The key observation is that such a structure is uniquely determined up to equivalence by certain triple products.This work is partially supported by NSF grant 相似文献
19.
O. A. Savinskaya A. P. Nemudry A. N. Nadeev S. V. Tsybulya N. Z. Lyakhov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(8):1053-1054
The structure of high-temperature SrFe1 − x
Mo
x
O3 − z
(0 ≤ x ≤ 0.5) phases was studied. Such studies are necessary to understand the mechanism of oxygen transport in membrane materials
used for high-temperature oxygen separation. 相似文献
20.
Bochao?Liu Markus?Büscher Feng-Kun?Guo Christoph?Hanhart Ulf-G.?Mei?ner 《The European Physical Journal C - Particles and Fields》2009,63(1):93-99
We investigate the interplay between crossed channel final state interactions and the constraints from two-particle unitarity
for the reactions J/ψ→V
π
π and
VK[`(K)]VK\bar{K}
, where V is either ω or φ. Using a model where the parameters are largely constrained by other sources, we find that, although small, crossed channel
final state interaction can influence the amplitudes considerably, in special areas of phase space. These results cast doubt
on the inapplicability of unitarity constraints on production amplitudes as recently claimed in the literature. 相似文献