共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
E. M. Fernández G. Borstel J. M. Soler L. C. Balbás 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):245-248
The ionic and electronic structure of
(Al2O3)n(Ox)
clusters with n
16 and x
= 0,
1, 2 is studied by means of first principles density functional
calculations, norm-conserving pseudopotentials and a numerical
atomic basis set. The equilibrium geometries have been
determined by total energy minimization, starting with several
initial geometries for each cluster size. The trends obtained
for the atomic arrangements (structural isomers, coordination
numbers, disordered versus
ordered structures, etc.) and the electronic properties
(binding energies, Homo-Lumo gap and dipole moments) are
discussed. For most of the oxidized clusters studied here we
find that the Homo-Lumo gap and the magnitude of dipole moment
of isomeric species can vary drastically. 相似文献
3.
C. Bobbert S. Schütte C. Steinbach U. Buck 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(2):183-192
The interaction of large ammonia and water clusters in the size range from <n> = 10 to 3 400 with electrons is investigated in a reflectron time-of-flight mass spectrometer. The clusters are generated
in adiabatic expansions through conical nozzles and are nearly fragmentation free detected by single photon ionization after
they have been doped by one sodium atom. For ammonia also the (1+1) resonance enhanced two photon ionization through the state with v = 6 operates similarly. In this way reliable size distributions of the neutral clusters are obtained which are analyzed in
terms of a modified scaling law of the Hagena type [Surf. Sci. 106, 101 (1981)]. In contrast, using electron impact ionization, the clusters are strongly fragmented when varying the electron
energy between 150 and 1 500 eV. The number of evaporated molecules depends on the cluster size and the energy dependence
follows that of the stopping power of the solid material. Therefore we attribute the operating mechanism to that which is
also responsible for the electronic sputtering of solid matter. The yields, however, are orders of magnitude larger for clusters
than for the solid. This result is a consequence of the finite dimensions of the clusters which cannot accommodate the released
energy.
Received 21 November 2001 相似文献
4.
A.M. Vichare D.G. Kanhere 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(1):89-94
Density based molecular dynamics has been used to investigate the ground state structures of heterogeneous binary clusters
Al13Lin, n
= 1, 2, 3, 4, 10, 19, 20, 21. Some of these structures have also been investigated by full Kohn-Sham based calculations. Our
earlier investigations have shown that in the Al-Li cluster, the ground state configurations are the ones where the Al atoms
form a core around which the Li atoms form a “cage”. In the present work, we have chosen the well-known Al13 icosahedron as the surface over which we study the evolution of the surface coverage as the number of Li atoms increases.
On the basis of the earlier work, we expect that the Al13Li20 cluster would be the most stable and indeed our simulations do yield such a novel fivefold symmetric stable structure formed
out of purely metal atoms. This icosahedral substrate is also used to study the coverage of the aluminum surface by lithium
atoms. For a small number of Li atoms, these studies suggest that the Li-Li dimerisation is not particularly favored.
Received: 24 October 1997 / Revised: 7 April 1998 / Accepted: 29 June 1998 相似文献
5.
T. Miyazaki H. Hiura T. Kanayama 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):241-244
We present a density-functional study of electronic
structures of convex-caged Si clusters doped with
transition-metal (TM) atoms. First, we show the reason for their
peculiar geometries in terms of interplay among the electron
orbitals of Si and TM atoms. Then we describe the potential
ability of the clusters to serve as charge sources to other
objects such as Si crystal surfaces. Millennium
Research for Advanced Information Technology (MIRAI)
Project. 相似文献
6.
P. Andersson C. Steinbach U. Buck 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):53-56
The structure of large water clusters of known size
distributions 〈n〉 = 20-2000
is investigated by vibrational spectroscopy of the OH stretch
mode. The water clusters are predissociated by a pulsed tunable
infrared optical parametrical oscillator (OPO) in the frequency
range 2800-3800 cm-1. Their fragments
are detected off-axis by electron impact ionization and mass
analyzed by a quadrupole mass spectrometer. The largest ion
signal stems from the neutral water hexamer fragment. The ion
yield is investigated at certain wavelengths while the size of
the clusters is varied, and for certain sizes complete
absorption spectra of the OH stretch motion are measured.
Fingerprints of the different coordination types of the water
molecules in the clusters are found and it turns out that our
method is especially sensitive to amorphous structures with
frequencies shifting in the range of 3300-3400
cm-1. 相似文献
7.
G. E. Ntamack F. Chandezon B. Manil H. Lebius S. Tomita C. Guet M. G. Kwato Njock B. A. Huber 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):153-156
Highly charged sodium clusters produced in collisions
between neutral clusters and multiply charged ions are formed
within a large range of temperatures and fissilities, and
identified by means of a high-resolution reflectron-type
time-of-flight mass spectrometer ( m/m
14000). The limit of stability of these charged clusters is
experimentally investigated, and the time-of-flight spectra are
compared with theoretical spectra based on Monte-Carlo
simulations. The results indicate that the maximum fissility
(X) of stable clusters is
approaching the Rayleigh limit (X = 1) for larger clusters sizes. It is
mainly limited by the initial neutral cluster temperature (
T 100 K) and the energy
transfer in the ionizing collision. In addition, the comparison
between the measured and simulated spectra suggests for high
cluster charges a multi-fragmentation process, in which most of
charge is emitted, creating low charged residual cluster ions. 相似文献
8.
S. Tomita J.S. Forster P. Hvelplund A.S. Jensen S.B. Nielsen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):119-122
We have measured attenuation cross sections and fragmentation cross sections for protonated water clusters H(H2O)n
+ (n = 1 to 100) colliding with noble gas atoms (He and Xe) at a laboratory energy of 50 keV. In collisions with He, a transparency
effect in the attenuation cross section was observed. For the case of fragmentation in collisions with Xe, a strong enhancement
of small clusters was observed which we attribute to multifragmentation.
Received 30 November 2000 相似文献
9.
A. Fielicke G. Meijer G. von Helden 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):69-72
Infrared spectra in the range of 530–1400
cm–1 are presented for tantalum oxide
cluster cations
(x = 3, 4 and 6). These spectra are
obtained via multiple photon
dissociation (MPD) spectroscopy of free cluster cations moving
in a molecular beam. The IR spectra for
are compared to spectra of
as well as to the experimental data
available for vanadium oxide cluster cations from IR-MPD
spectroscopy. For
and
the IR spectra exhibit very strong
similarities (including the band positions), whereas absorption
bands in
are relatively blue-shifted by
about 20–40 cm–1. 相似文献
10.
N.T. Wilson R.L. Johnston 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):161-169
Molecular Dynamics Simulated Annealing has been used to probe the structure of small Au clusters consisting of between 2 and
40 atoms. The interatomic interactions within these clusters are described using an empirical Murrell-Mottram many-body potential
energy function. Four distinct structural motifs are present in the structures of the predicted global minima, based on octahedra,
decahedra, icosahedra and hexagonal prisms.
Received 30 September 1999 and Received in final form 23 March 2000 相似文献
11.
Magnetism in Rh clusters under hydrostatic deformations 总被引:1,自引:0,他引:1
E.O. Berlanga-Ramırez F. Aguilera-Granja A. Dıaz-Ortiz A. Vega 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):343-349
The magnetic behavior of rhodium clusters RhN (N = 4-38) under hydrostatic deformations was investigated. The starting cluster structures were obtained from an evolutionary
search algorithm applied to a Gupta potential. The spin-polarized electronic structure and related magnetic properties were
calculated using a self-consistent spd tight-binding Hamiltonian within the unrestricted Hartree-Fock approximation. The magnetic behavior was analyzed in terms
of the interdependence between the geometrical parameters and the electronic structure. Anomalous magnetic effects were found
in some cases.
Received 5 August 2002 / Received in final form 10 January 2003 Published online 4 March 2003
RID="a"
ID="a"e-mail: berlanga@dec1.ifisica.uaslp.mx 相似文献
12.
O. Diéguez R.C. Longo C. Rey L.J. Gallego 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(4):573-576
Using the noncentral embedded atom model potential recently proposed by Besson and Morillo for bulk alloys (), we performed computer simulations to predict the ground-state configurations of and clusters (). The computed structures of clusters are in general agreement with such theoretical results as have been obtained by density functional calculations
(i.e. for ). The results for Fe-rich clusters show surface segregation of Al, which is in keeping with the findings of a previous study of clusters.
Received 29 April 1999 相似文献
13.
M. Hyslop A. Wurl S.A. Brown B.D. Hall R. Monot 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):233-236
A beam of Pb clusters is produced with the inert gas aggregation method and probed by electron diffraction. Analysis of the
diffraction patterns indicates that average cluster size can vary between 3 and 7 nm, according to nucleation conditions.
The diffraction patterns from beams with larger average cluster size are very similar to patterns calculated from model decahedron
clusters, while those for smaller cluster size do not appear to have simple geometrical face-centred cubic, decahedral, or
icosahedral structure.
Received 30 November 2000 相似文献
14.
S. A. Nepijko D. N. Ievlev W. Schulze 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):115-117
The plasmon energy of Ag clusters produced on an amorphous
carbon substrate by gas-aggregation technique has been measured.
It has been determined from the plasmon peak position in the
light emission spectrum obtained during bombardment of Ag
clusters by low-energy electrons. For Ag cluster films with
maximum of the cluster size distribution at 30, 8 and 2.5 nm,
the plasmon energy comprised 3.76, 4.13 and 4.28 eV (the
wavelength was 330, 300 and 290 nm), respectively. The blue
shift of the plasmon energy is probably related to the effect of
confounding of collective and single-particle excitations. 相似文献
15.
Y. Tai J. Murakami K. Saito M. Ikeyama K. Tajiri M. Watanabe S. Tanemura T. Mizota 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):261-263
Plasma desorption mass spectrometry has been applied to
characterization of dodecanthiol-passivated gold nanoparticles.
An overview of the experimental set-up and mass analyses for the
nanoparticles prepared in different conditions are shown. Mass
distributions were found to shift to higher mass regions with
increasing reaction temperature and reaction period. The results
are consistent with those of transmission electron microscopy
observations, UV-visible absorption spectra and also with a
reported laser desorption mass spectrometry. 相似文献
16.
F. Baletto C. Mottet R. Ferrando 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):233-236
The possibility of obtaining core-shell nanoparticles by
depositing adatoms of a different element B above a cluster of
an element A (system B/A) is studied by Molecular Dynamics
simulations. We consider the four cases Ag/Cu, Cu/Ag, Ag/Pd and
Pd/Ag, which present very different behaviours, and investigate
whether it is possible to build up of well-defined core-shell
structures. 相似文献
17.
K. Manninen M. Manninen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):243-249
Ground state geometries of small hard sphere clusters were studied using two different type of contact interaction, a pair-potential
and a many-atom interaction. Monte Carlo method in an FCC lattice with all possible (111) stacking faults was used to obtain
the minimum energy geometries for clusters up to 59 atoms. Due to the surface energy, FCC packing is generally favoured as
opposite to the HCP structure. However, in most cluster sizes the ground state obtained with the many-atom interaction has
one or more stacking faults. The most symmetric geometry is usually not the ground state. Clusters with 59 and 100 atoms were
studied due the possibility of a high symmetry cluster with stacking faults in all four directions. The size dependence of
the total energy has similarities with that of the average moment of inertia.
Received 6 February 2002 / Received in final form 11 April 2002 Published online 19 July 2002 相似文献
18.
W. Vervisch C. Mottet J. Goniakowski 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):311-314
Morphology and atomic structure of supported Pd clusters
on MgO(100) substrate are investigated theoretically using a
mixed approach: a semi-empirical potential for the metal bonding
within the cluster and a potential fitted to
ab initio calculations for
the metal-oxide interaction. We find that the clusters adopt a
truncated pyramidal morphology in agreement with experimental
results. The detailed study of the epitaxial relation as a
function of cluster size shows the existence of a critical size
around 3 nm where elastic strain due to the misfit between the
substrate and the deposit is released by the introduction of
interfacial dislocations. 相似文献
19.
F. Hagelberg C. Xiao B. Marsen M. Lonfat P. Scheier K. Sattler 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(1):37-41
In a series of recent experiments, the HOMO-LUMO energy gaps of small Si clusters deposited on a graphite substrate have been
determined by Scanning Tunneling Microscopy (STM). The values obtained were found to be substantially smaller than the energy
gaps of corresponding passivated clusters. This work considers dimensional reduction as a possible mechanism for a sizeable
energy gap narrowing by the example of the system Si5. The impact of the graphite substrate on the deposited species is investigated in the framework of a pseudocluster model.
Received 30 November 2000 相似文献
20.
Y. Chushak L.S. Bartell 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):43-46
A set of molten gold clusters, each with 1157 gold atoms, was studied by molecular dynamics simulations as the clusters underwent
freezing at three different temperatures. Most of the clusters attained an icosahedral structure upon freezing, a structure
found to be stable to mild annealing. Other structures observed were imperfect truncated decahedral, truncated octahedral
and hexagonal close packed structures. The role of kinetics in the process of cluster solidification is discussed.
Received 6 November 2000 相似文献