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1.
M.P. Machado P. Piquini R. Mota 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(1):91-93
The geometric structures, energetics and electronic properties of the recently discovered BN nanocones are investigated using
first-principles calculations based on the density-functional theory. We have proposed one particular structure for BN nanocones
associated with the 240° disclination, derived by the extraction of four 60° segments, presenting as characteristic four pentagons at the apex and termination in two atoms. The cones are simulated by
three clusters containing 58 B plus N atoms and additional 12 H atoms to saturate the dangling bonds at the edge. The most
stable configuration is obtained when the two terminating atoms are one B and one N. For the cases where the two terminating
atoms are of the same kind, the tip with B atoms is determined to have lower binding energy than with N atoms. The local densities
of states of these BN nanocones are investigated and sharp states are found in the regions close (below and above) to the
Fermi energy.
Received 14 October 2002 / Received in final form 6 December 2002 Published online 11 February 2003
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ID="a"e-mail: ppiquini@smail.ufsm.br 相似文献
2.
H. Yasuda K. Furuya 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(2):279-283
Alloying behavior and phase stability has been studied in situ by transmission electron microscopy using clusters in the Au-Sn system. When tin atoms are vapor-deposited onto nm-sized
gold clusters, rapid dissolution of tin atoms into gold clusters takes place and as a result Au-rich solid solution, amorphous-like
Au-Sn alloy and AuSn compound clusters are formed depending upon the concentration of tin. The remarkable enhancement of solubility
has been observed in Au-rich solid solution and AuSn compound. It becomes more difficult to form two phases in the interior
of individual clusters even if the composition of alloy clusters falls in the two-phase region in the phase diagram for the
bulk alloy and as a result amorphous-like phase is stabilized in nm-sized Au-Sn alloy clusters.
Received 2 August 1999 and Received in final form 8 November 1999 相似文献
3.
R. Lazzari I. Simonsen D. Bedeaux J. Vlieger J. Jupille 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(2):267-284
The light scattering by three-dimensional clusters supported by a substrate is modelled by representing clusters by truncated
spheroids whose polarizability is calculated via a multipolar development of the potential in the quasi-static limit. The determination of the mean island radius, density
and aspect ratio from the optical response is examined. The strong influence of both the particle-substrate interaction and
the particle shape on the optical behaviour is demonstrated, showing the limits of effective medium and dipolar theories.
The Surface Differential Reflectance spectra of silver on MgO(100) and titanium or aluminium on α-Al2O3(0001) surfaces have then been modelled by using the above model, illustrating the capability of optical means to deal with
various metals, including those belonging to transition series. In all cases, it is highlighted that the aspect ratio is central
in modelling the optical response of supported particles.
Received 5 June 2000 and Received in final form 31 July 2001 相似文献
4.
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
5.
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
6.
M. Amoruso I. Meccoli A. Minguzzi M.P. Tosi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(3):441-447
We evaluate the small-amplitude excitations of a spin-polarized vapour of Fermi atoms confined inside a harmonic trap. The
dispersion law is obtained for the vapour in the collisional regime inside a spherical trap of frequency , with n the number of radial nodes and the orbital angular momentum. The low-energy excitations are also treated in the case of an axially symmetric harmonic confinement.
The collisionless regime is discussed with main reference to a Landau-Boltzmann equation for the Wigner distribution function:
this equation is solved within a variational approach allowing an account of non-linearities. A comparative discussion of
the eigenmodes of oscillation for confined Fermi and Bose vapours is presented in an Appendix.
Received 23 February 1999 and Received in final form 21 April 1999 相似文献
7.
D.K. Yu R.Q. Zhang S.T. Lee 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(1):57-63
The structures and energetics of carbon bridged C60 clusters (C
60
)
n
Cm have been studied by simulated annealing technique within the tight-binding molecular-dynamics. The “sp2 addition” ball-and-chain dimers exhibit odd-even alternations over the number of chain atoms, with the dimers containing
even chain atoms more stable against dissociation than their immediate neighbors containing odd chain atoms. In addition to
the usual “sp2 addition” dimers, a pentagon-linked C121 isomer and a hexagon-linked C122 isomer are also found to be stable. Based on our tight-binding calculations, trimers and larger clusters can be simply regarded
as being made up of independent or weakly interacting dimers, if the C-C60 joints on a single cage are not too close to each other. Large C60 clusters connected by chains each containing only one or two carbon atoms have similar stability to that of constituent dimers,
indicating the possibility to form stable C60-carbon polymers.
Received 17 January 2001 and Received in final form 26 February 2001 相似文献
8.
F.A. Gianturco F. Sebastianelli 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(3):399-414
The structural properties of some of the smaller ionic clusters of neon atoms are examined at the post-Hartree-Fock level
using a variety of correlation corrections described within a Density Functional treatment. The results of the calculations,
and the physical reliability of the method, are discussed in comparison with earlier theoretical results and with the scanty
experimental data. The possible presence of a dimeric ion as the core ionic moiety of all the clusters is indicated by the
present treatment which also underlines the weaker binding of the outer “shells” of Ne atoms to the central moiety and the
rather marked overall charge localization into the central ionic core of the clusters.
Received 30 December 1999 and Received in final form 29 February 2000 相似文献
9.
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
10.
M. Bertolus V. Brenner P. Millié 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(2):197-205
A theoretical study of clusters with using density functional theory is presented. Tests of various functionals demonstrate that local spin density approximation
(LSDA) is the most adequate functional for the study of these systems. Structures, vibrational frequencies, and IR intensities
of the lowest energy isomer of the studied clusters obtained using LSDA are described, and the unusual properties of the Si-C
clusters are discussed. A quantitative analysis of the obtained structures was carried out, and relations between the coordinations,
interatomic distances, and angles observed in the Si-C clusters were obtained through introduction of the notion of coordination.
This analysis also shows that the carbon atoms mainly exhibit sp and sp2 hybridizations, and that a majority of silicon atoms do not hybridize. This study is the fi
rst step of the implementation of a semi-empirical potential, which would describe the moderately small Si-C clusters.
Received: 20 October 1997 / Received in final form: 16 December 1997 / Accepted: 17 December 1997 相似文献
11.
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
12.
C. Nützenadel A. Züttel D. Chartouni G. Schmid L. Schlapbach 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(2):245-250
Metal hydrides are used for electrochemical or gaseous storage of hydrogen because considerable amounts of hydrogen are reversibly
absorbed and desorbed at interstitial sites. Palladium is often used as a model system. Nanophase material is of interest
because properties related to the hydrogen absorption are size dependent. In this study, clusters from the size of 55 to 1415
atoms are investigated and compared with bulk Pd. It turns out that not only the amount of hydrogen per palladium that can
be intercalated changes but also kinetics and chemical potentials are dependent on the cluster size. The clusters used for
this study were chemically synthesised and stabilised by a ligand shell.
Received 9 October 1998 and Received in final form 10 May 1999 相似文献
13.
F. Despa W. Bouwen F. Vanhoutte P. Lievens R.E. Silverans 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(3):403-411
The influence of doping of Li-clusters by electronegative O and C atoms on the ionization potentials was investigated. Experimentally,
we report ionization potentials for bare Lin clusters deduced from photoionization efficiency spectra. The values are compared with the results for LinO and LinC clusters. Observed differences are largely attributed to a quantum size effect caused by the segregated molecular part around
the impurity, which changes the electron work function. Theoretically, the Fermi and exchange-correlation energies which enter
the work function, are calculated in the frame of the augmented plane wave (APW) method by taking explicitly into account
the presence of the molecular core. The other contribution to the work function, the moment of the double layer at the cluster
surface, is computed by solving the corresponding Poisson's equation.
Received 9 September 1999 and Received in final form 7 February 2000 相似文献
14.
J.C. Pivin M.A. García H. Hofmeister A. Martucci M. Sendova Vassileva M. Nikolaeva O. Kaitasov J. Llopis 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):251-260
Precipitation of silver clusters in silica is achieved by different methods: ion implantation, ion beam mixing of superimposed
layers and ion irradiation of films deposited by means of co-sputtering or sol-gel technique. Main features of the nanoparticles
depending on the preparation method are investigated by TEM. The optical extinction resonance of these clusters is analysed
in terms of sizes and interaction between the clusters on the basis of calculations. We found that resonances in sputtered
and gel films with low metal concentrations are well described by plasmon polaritons in isolated clusters and calculations
based on Mie theory allow the study of their growth under irradiation. This theory is not appropriate to describe the optical
response of silver clusters in silica implanted with Ag concentrations higher than 5 at.% or in ion beam mixed films, because
of the interaction between clusters. Using an effective medium model, it is demonstrated that the random dispersion of clusters
in implantation films causes fluctuations and, on average, an increase of the clusters polarization. On the contrary, the
particular arrangement of the clusters with a bimodal size distribution in ion beam mixed films induces a screening effect
between the clusters of largest size.
Received 10 January 2002 / Received in final form 26 April 2002 Published online 19 July 2002 相似文献
15.
C. Herwig J.A. Becker 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):51-54
The growth of small tellurium clusters in helium and the influence of a metal impurity (dysprosium atoms) on the cluster size
distribution are investigated in a double laser vaporization source. A model describing the role of the carrier gas as collision
partner is presented, emphasizing the crucial influence of the gas pressure on cluster formation. Changes in cluster reactivity
due to dysprosium addition are discussed in terms of ionic structures Dy
3 +(Te
N)3 - containing a radical electron.
Received 28 November 2000 相似文献
16.
V. Kumar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):227-232
We report the recent findings of metal (M) encapsulated
clusters of silicon from computer experiments based on
ab initio total energy
calculations and a cage shrinkage and atom removal approach. Our
results show that using a guest atom, it is possible to wrap
silicon in fullerenelike (f)
structures, as sp2 bonding is not
favorable to produce empty cages unlike for carbon. Transition M
atoms have a strong bonding with the silicon cage that are
responsible for the compact structures. The size and structure
of the cage change from 14 to 20 Si atoms depending upon the
size and valence of the M atom. Fewer Si atoms lead to
relatively open structures. We find cubic,
f, Frank-Kasper (FK)
polyheral type, decahedral, icosahedral and hexagonal structures
for M@Sin with n = 12-16 and several different M
atoms. The magic behavior of 15 and 16 atom Si cages is in
agreement with experiments. The FK polyhedral cluster,
M@Si16 has an exceptionally large density
functional gap of about 2.35 eV calculated within the
generalized gradient approximation. It is likely to give rise to
visible luminescence in these clusters. The cluster-cluster
interaction is weak that makes such clusters attractive for
cluster assembled materials. Further studies to stabilize
Si20 cage with M = Zr, Ba, Sr, and Pb
show that in all cases there is a distortion of the
f cage. Similar studies on M
encapsulated germanium clusters show FK polyhedral and
decahedral isomers to be more favorable. Also perfect
icosahedral M@Ge12 and
M@Sn12 clusters have been obtained with
large gaps by doping with divalent M atoms. Recent results of
the H interaction with these clusters, hydrogenated silicon
fullerenes as well as assemblies of clusters such as nanowires
and nanotubes are briefly presented. 相似文献
17.
G.M. Koretsky M.B. Knickelbein 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(3):273-278
The photoionization spectra of Pr2-Pr21 and Ce2-Ce17 have been measured near threshold. The ionization potentials (IPs) of and vary discontinuously with size, but trend downward toward the work function of the bulk metals. In general, the IPs of cerium
clusters display more variation than those of praseodymium clusters. The sudden discontinuities observed in the IPs of both
and is akin to that displayed by clusters of transition metal atoms, suggesting that as in transition metal clusters, the rapid
evolution in geometric structure with size is the source of these discontinuities.
Received: 2 January 1998 / Accepted: 10 March 1998 相似文献
18.
P.A. Marcos J.A. Alonso A. Rubio M.J. López 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,6(2):221-233
The thermal stability, phases and phase changes of small carbon clusters and fullerenes are investigated by constant energy
Molecular Dynamics simulations performed over a wide range of temperatures, i.e., from to above the melting point of graphitic carbon. The covalent bonds between the carbon atoms in the clusters are represented
by the many-body Tersoff potential. The zero temperature structural characteristics of the clusters, i.e., the minimum energy structures as well as the isomer hierarchy can be rationalized in terms of the interplay between the
strain energy (due to the surface curvature) and the number of dangling bonds in the cluster. Minimization of the strain energy
opposes the formation of cage structures whereas minimization of the number of dangling bonds favors it. To obtain a reliable
picture of the processes experienced by carbon clusters as a function of temperature, both thermal and dynamical characteristics
of the clusters are carefully analyzed. We find that higher excitation temperatures are required for producing structural
transformations in the minimum energy structures than in higher lying isomers. We have also been able to unambiguously identify
some structural changes of the clusters occurring at temperatures well below the melting-like transition. On the other hand,
the melting-like transition is interrupted before completion, i.e., the thermal decomposition of the clusters (evaporation or ejection of or units) occurs, from highly excited configurations, before the clusters have fully developed a liquid-like phase. Comparison
with experiments on the thermal decomposition of and a discussion of the possible implications of our results on the growth mechanisms leading to the formation of different
carbon structures are included.
Received: 25 March 1998 / Received in final form: 30 October 1998 相似文献
19.
C. Bobbert C.P. Schulz 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):95-97
Nam(H2O)n Clusters ( n = 1...200, m = 1...50) are formed in a recently build pick-up arrangement. Preformed water clusters traverse a sodium oven, where sodium
atoms are picked up. At low sodium vapour pressure ( < 1×10-4 mbar) pure Na(H2O)n clusters are observed in the mass spectra. At high sodium vapour pressure ( > 1×10-3 mbar) the water cluster pick up more than 50 Na atoms and reaction products Na(NaOH)n ( n = 2, 4...50) dominate the mass spectra. The even number of NaOH units in the products indicate that also in a finite cluster
the reaction occurs in pairs as in the macroscopic reaction.
Received 4 December 2000 相似文献
20.
D. Zanghi A. Traverse J.-P. Dallas E. Snoeck 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):171-179
Ni ions were implanted in bulk AlN with the goal to form embedded metallic clusters. Combining several characterisation techniques
such as X-ray absorption spectroscopy, X-ray diffraction and high resolution transmission electron microscopy, we determined
the lattice parameter of the Ni clusters that display a fcc crystalline structure. The average size increases when the ion
fluence is increased or after a thermal treatment. Thanks to moiré fringes observed by high resolution transmission electron
microscopy and to satellite peaks seen on the diffraction patterns, we concluded that the annealed Ni clusters orientate their
(002) planes on the (101) of AlN. Moreover, the satellite positions allowed us to calculate Ni cluster average diameters,
that are in agreement with average sizes deduced by X-ray absorption spectroscopy.
Received 25 August 1999 and Received in final form 8 February 2000 相似文献