共查询到10条相似文献,搜索用时 140 毫秒
1.
A. N. Pestryakov V. V. Lunin D. I. Kochubey A. Yu. Stakheev E. Smolentseva 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,34(1-3):55-58
The influence of modifying additives of Ce, Zr, La and Cs
oxides on changes of electronic state of supported copper during the
catalytic reaction of butane complete oxidation has been studied by the
methods of IR-spectroscopy of adsorbed CO, XPS, EXAFS and XRD. The modifying
additions of cerium and zirconium oxides stabilize the ionic state of
copper, while lanthanum and cesium oxides decrease the effective charge of
copper ions. The observed effects are caused by variation in metal
dispersivity in the modified samples and by electron donor-acceptor
interaction of the surface atoms and ions of copper with the modifier. 相似文献
2.
C. Bréchignac Ph. Cahuzac B. Concina J. Leygnier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):91-94
We have studied experimentally the collisional charge transfer between a neutral atom and a multicharged metal-atom cluster.
The charge transfer cross section measured for Na 31
+ + + Cs is in the range of 400 ?2. The time-of-flight mass analysis of the singly charged collision products demonstrates that an energy of about 0.5 eV is
deposited in the cluster fragment during the charge transfer collision. This effect can be interpreted as a charge transfer
to an excited state of the metal cluster. The measured cross section for Na 31
+ + + Cs is larger than the one for Na 31
+ + Cs collisions. This difference between these two systems is due to the existence, for the first one, of a Coulombic repulsion
term in the collision output channel.
Received 24 October 2000 相似文献
3.
F. Fehrer P. M. Dinh M. Bär P.-G. Reinhard E. Suraud 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):447-458
We investigate the dynamical evolution of a Na8 cluster embedded in Ar matrices of various sizes from N=30 to 1048.
The system is excited by an intense short laser pulse leading to high
ionization stages.We analyze the subsequent highly non-linear motion of cluster and Ar environment in terms of trajectories,
shapes, and energy flow.
The most prominent effects are: temporary stabilization of high charge states for several ps, sudden stopping of the Coulomb
explosion of the embedded Na8
clusters associated with an extremely fast energy transfer to the Ar
matrix, fast distribution of energy throughout the Ar layers by a sound wave.
Other ionic-atomic transfer and relaxation processes proceed at slower
scale of few ps. The electron cloud is almost thermally decoupled
from ions and thermalizes far beyond the ps scale. 相似文献
4.
Y. F. Ouyang D. M. Zhai J. Fang P. Xiang Y. Du Y. H. He 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(3):629-641
The geometries and electronic structural properties of AB and ABC (A, B, C = Al, Fe, Zr, Ce) microclusters have been systematically
investigated by using a hybrid density-functional method (B3LYP) approach. The spectroscopic constants of ground-state AB
and ABC (A, B, C = Al, Fe, Zr, Ce) are obtained, and are found to be in agreement with other available experimental and theoretical
results. The calculated gaps between highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO)
are clearly changed when X is doped into the AB dimers (X = Al, Fe, Zr, Ce). The calculated results indicate that a triangular
form with D3h, C2v or Cs symmetry is the most stable for the corresponding ABC trimers, and, in addition, the possible isomers (linear structure)
with D∞h or C∞v symmetry of three-atom clusters were found to be of higher energies. We conclude that AlFe and Al2Fe have the highest chemical stability of all the AB dimers and ABC trimers, respectively, due to the high HOMO-LUMO gap.
We also find that the binding energy of Ce3 is the largest in magnitude among all ABC (A, B, C = Al, Fe, Zr, Ce) trimers, as is the case with Ce2 among all AB (A, B, C = Al, Fe, Zr, Ce) dimers. The most stable geometry, charge transfer and possible dissociation channels
are also discussed. 相似文献
5.
N. Nishi K. Kosugi K. Hino T. Yokoyama 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):97-100
A new type of Co-C nanoparticles is synthesized from
CH2Cl2 solution of
Co4(CO)1
2 by heating up to 210
°C in a closed vessel. Transmission
electron microscope (TEM) and electron energy loss spectroscopy
(EELS) observation show that the particles are embedded in
amorphous carbon and their average size is 12 nm. The radial
structure function obtained from the extended X-ray absorption
fine structure (EXAFS) of the Co K-edge absorption of the Co-C
nanoparticles provides a Co-C average distance of 2.08 Å and the
Co-Co distances of 3.18 Å and 3.9 (±0.2) Å. The particles
exhibit the magnetic hysteresis curve with a coercive force of
200 Oe at 20 K and 260 Oe at 300 K. The temperature dependence
of the magnetic susceptibility measured under zero-field cooling
and 10 Oe field cooling conditions exhibits the behavior
characteristic of a set of single magnetic domain nanomagnets in
an amorphous carbon matrix. 相似文献
6.
7.
R. Guirado-López D. Spanjaard M.-C. Desjonquères A.M. Oleś 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(4):437-446
We analyze the stability of magnetic states obtained within the tight-binding model for cubooctahedral (Oh) and icosahedral (Ih) clusters of early 4d (Y, Zr, Nb, Mo, and Tc) transition metals. Several metastable magnetic clusters are identified which suggests the existence
of multiple magnetic solutions in realistic systems. A bulk-like parabolic behavior is observed for the binding energy of
Oh and Ih clusters as a function of the atomic number along the 4
d-series. The charge transfer on the central atom changes sign, while the average magnetic moments present an oscillatory behavior
as a function of the number of d electrons in the cluster. Our results are in agreement with other theoretical calculations.
Received: 20 November 1997 / Received in final form: 9 March 1998 / Accepted: 30 March 1998 相似文献
8.
C. Yannouleas U. Landman A. Herlert L. Schweikhard 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):81-85
Using Penning-trap experiments and a shell-correction method incorporating ellipsoidal shape deformations, we investigate
the formation and stability patterns of trianionic gold clusters. Theory and experiment are in remarkable agreement concerning
appearance sizes and electronic shell effects. In contrast to multiply cationic clusters, decay of the trianionic gold clusters
occurs primarily via electron autodetachment and tunneling through a Coulomb barrier, rather than via fission.
Received 9 January 2001 相似文献
9.
P. Priyadharsini A. Pradeep B. Sathyamoorthy G. Chandrasekaran 《Journal of Physics and Chemistry of Solids》2014
Room temperature multiferroic properties of BiFeO3 (BFO), Bi0.9La0.1FeO3 ((La)BFO) and Bi0.9La0.075Ce0.025FeO3 ((La,Ce)BFO) nanoparticles have been reported in this paper. XRD (X-ray diffraction) analyses of the nanoparticles show a decrease in the lattice constants and cell volume with the substitution of La and Ce. It is evident from the SEM (scanning electron microscope) micrographs that the (La,Ce) co-doped sample possesses dense microstructure made of smaller particles. Raman study accounts for the weakening of the strong hybridization between Bi-O by the substitution of La and Ce ions. This is also accompanied by an increase in the remanent magnetization, dielectric constant, and ferroelectric polarization. BFO nanoparticles show exchange bias effect under an applied magnetic field while the (La)BFO and (La,Ce)BFO samples show no trace of such effect. Ac-conductivity of (La,Ce) co-doped sample is observed to be several orders lesser in magnitude than bulk BFO ceramics. These results are interpreted by means of the subtle change in the structure, suppression of the spin cycloid and reduction of oxygen vacancies in the doped samples. 相似文献
10.
I. L. Garzón M. R. Beltrán G. González I. Guterrez-González K. Michaelian J. A. Reyes-Nava J. I. Rodrguez-Hernández 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):105-109
Theoretical and experimental information on the shape and
morphology of bare and passivated gold clusters is fundamental
to predict and understand their electronic, optical, and other
physical and chemical properties. An effective theoretical
approach to determine the lowest-energy configuration (global
minimum) and the structures of low energy isomers (local minima)
of clusters is to combine genetic algorithms and many-body
potentials (to perform global structural optimizations), and
first-principles density functional theory (to confirm the
stability and energy ordering of the local minima). The main
trend emerging from structural optimizations of bare Au clusters
in the size range of 12-212 atoms indicates that many
topologically interesting low-symmetry, disordered structures
exist with energy near or below the lowest-energy ordered
isomer. For example, chiral structures have been obtained as the
lowest-energy isomers of bare Au28 and
Au55 clusters, whereas in the size-range
of 75-212 atoms, defective Marks decahedral structures are
nearly degenerate in energy with the ordered symmetrical
isomers. For methylthiol-passivated gold nanoclusters
[Au28(SCH3)16
and
Au38(SCH3)24],
density functional structural relaxations have shown that the
ligands are not only playing the role of passivating molecules,
but their effect is strong enough to distort the metal cluster
structure. In this work, a theoretical approach to characterize
and quantify chirality in clusters, based on the Hausdorff
chirality measure, is described. After calculating the index of
chirality in bare and passivated gold clusters, it is found that
the thiol monolayer induces or increases the degree of chirality
of the metallic core. We also report simulated high-resolution
transmission electron microscopy (HRTEM) images which show that
defects in decahedral gold nanoclusters, with size between 1-2
nm, can be detected using currently available experimental HRTEM
techniques. 相似文献