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1.
G. Ballentine M. Heßler M. Kinza K. Fauth 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):535-537
Fe clusters of 105±2 atoms/cluster were mass selectively deposited onto Cu(111) at cryogenic temperatures.
XMCD was used to measure temperature and direction dependent magnetization curves.
The clusters are superparamagnetic at the lowest temperature measured (10 K). Their magnetization curves are consistent with
magnetic moments of ≈2.5μB per atom which are thus enhanced over the bulk values.
Within experimental accuracy, the clusters do not present magnetocrystalline anisotropy in the temperature range
of 10 K to 60 K. 相似文献
2.
J. Bansmann A. Kleibert F. Bulut M. Getzlaff P. Imperia C. Boeglin K.-H. Meiwes-Broer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):521-528
Mass-filtered cobalt clusters with a size of 8 nm have been deposited in-situ under soft-landing conditions onto Au(111).
The spin and orbital moments of the Co nanoparticles on a Au (111) single crystal have been investigated as a function of
the temperature using the element-specific method of X-ray magnetic circular dichroism in photoabsorption. The results hint
at an temperature-dependent spin-reorientation transition which is discussed with respect to different contribution to the
magnetic anisotropy. Furthermore, by means of an in-situ oxidation experiment, the influence of an exposure to oxygen on the
properties of the cobalt clusters has been investigated. 相似文献
3.
N. Fujima T. Oda 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):89-92
Atomic structures and non-collinear magnetic moments are
calculated by the first principle molecular dynamics for
Fe5 and Fe6 linear
chains with several fixed and free chain-lengths. The
dimerization appears in the optimized atomic structures of all
the chains. For the Fe5, the magnetic
arrangement is parallel for a large chain-length and changes to
non-collinear with decreasing the chain-length. For the
Fe6, the magnetic arrangement is
antiparallel in a unit of dimer for a small chain-length and
changes to non-collinear with increasing the chain-length. These
magnetic behaviors are simulated by a simple
J1-J2 Heisenberg
model. 相似文献
4.
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
5.
H. Shiroishi T. Oda H. Sakashita N. Fujima 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):129-132
We have studied the electronic structure of the carbon nanotubes which
include Fe atomic wire with using the density functional theory.
As the stable geometries, we obtained the straight and zigzag wires,
which have ferromagnetic and antiferromagnetic alignments, respectively.
The antiferromagnets consists of the two ferromagnetic dimers which
couple in antiparallel alignment.
We presents the band dispersions and the density of states for the
magnetic nanotubes.
The electronic structure at the Fermi level consists of the
Fe 3d and C 2pπ states, which shows a strong hybridization
between them. 相似文献
6.
D. V. Kolesnikov V. A. Osipov 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(4):465-470
The low-energy electronic structure of icosahedral
fullerenes is studied within the field-theory model. In the field
model, the pentagonal rings in the fullerene are simulated by two
kinds of gauge fields. The first one, non-abelian field, follows
from so-called K spin rotation invariance for the spinor field
while the second one describes the elastic flow due to pentagonal
apical disclinations. For fullerene molecule, these fluxes are
taken into account by introducing an effective field due to
magnetic monopole placed at the center of a sphere.
Additionally, the spherical geometry of the
fullerene is incorporated via the spin connection term. The exact
analytical solution of the problem (both for the eigenfunctions
and the energy spectrum) is found. 相似文献
7.
M. Yamada H. Nishihara 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):257-260
Biferrocene-modified gold nanoparticles
(Aun-BFc) comprising 1.7, 2.2 and 2.9 nm
in average core diameter, d,
were synthesized by a substitution reaction of octyl
thiolate-covered nanoparticles with biferrocene-terminated
alkanethiol, 1-(9-thiononyl-1-one)-1, 1-biferrocene (BFcS).
All sizes of Aun-BFc undergo two-step
oxidation reactions in 0.1 mol dm-3
Bu4NClO4-CH2Cl2
and consecutive potential scans including the second oxidation
process lead to the formation of an adhesive redox-active gold
nanoparticle film on an electrode. The thickness of the
Aun-BFc film is controllable by the
number of potential scans. The scanning tunneling microscope
images reveal that the Aun-BFc (d = 2.9 nm) film forms many domains of
the assembled Aun-BFcs, especially the
particles are isotropically assembled in line. 相似文献
8.
M. Imamura T. Miyashita A. Tanaka H. Yasuda Y. Negishi T. Tsukuda 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):233-236
We have carried out optical and X-ray photoemission
studies of the dendrimer-encapsulated Au nanoclusters. The
dendrimer-encapsulated Au nanoclusters are prepared by the chemical
reduction of Au ions loaded within the dendrimer templates.
Photoluminescence spectrum of the dendrimer-encapsulated Au nanoclusters with
diameter of about 1.0 nm shows the visible luminescence centered at about
2.8 eV. In addition, we have measured the nanocluster-size dependent
photoemission spectra in the valence-band region. From line shape analysis
of Au 4f X-ray photoemission spectra, Au 4f core-level spectra of
the dendrimer-encapsulated Au nanoclusters reflect the size dependent
chemical-states. From these results, we discuss electronic structures and
chemical states of the dendrimer-encapsulated Au nanoclusters. 相似文献
9.
A. Srinivasan M. N. Huda A. K. Ray 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(2):227-236
Fullerene-like silicon nanostructures with twenty and twenty-four carbon
atoms on the surface of the Si60 cage by substitution, as well as
inside the cage at various orientations have been studied within the
generalized gradient approximation to density functional theory. Full
geometry optimizations have been performed without any symmetry constraints
using the Gaussian 03 suite of programs and the LANL2DZ basis set. Thus, for the
silicon atom, the Hay-Wadt pseudopotential with the associated basis set is
used for the core electrons and the valence electrons, respectively. For the
carbon atom, the Dunning/Huzinaga double zeta basis set is employed.
Electronic and geometric properties of these nanostructures are presented
and discussed in detail. Optimized silicon-carbon fullerene like
nanostructures are found to have increased stability compared to the bare
Si60 cage and the stability depends on the number and the orientation
of carbon atoms, as well as on the nature of silicon-carbon and
carbon-carbon bonding. 相似文献
10.
M.-H. Du L.-L. Wang A. Kolchin H.-P. Cheng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):323-326
The interaction of water with SiO
2 is an important problem in geophysics,
materials physics, and environmental science. In this paper, we
present recent results on studies of H
2
O-silica clusters from first-principles
Born-Oppenheimer molecular dynamics calculations. Bond strength
and chemical stability are investigated as a function of cluster
size and chemical composition. Both physisorption and
chemisorption of water molecules on the clusters are discussed
via analysis of energetics.
Calculations of clusters are compared with the results from
extended surfaces. The validity of clusters as models of
surfaces is discussed. 相似文献
11.
A. Md. Asaduzzaman M. Springborg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):213-216
Using a parameterized density-functional tight-binding method we have calculated the electronic and structural properties
of Ge–Si nanoparticles. Starting with a spherical part of a zinc-blende/diamond crystal (with the center of the sphere at
the mid-point of a nearest-neighbour bond) we have constructed initial structures that subsequently were allowed to relax.
Structures consisting solely of Ge atoms or solely of Si atoms were studied, together with core-shell structures for which
one semiconductor forms a shell on the core of the other semiconductor. Moreover, homogeneous, ordered SiGe structures as
well as structures with a semisphere of one semiconductor and a semisphere of the other were also considered.
In analysing the results special emphasis is put on identifying particularly stable structures, on explaining the occurrence
of those, on the spatial distribution of the frontier orbitals, and on the variation of the total energy with structure and
composition. 相似文献
12.
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
13.
M. Tchaplyguine S. Peredkov A. Rosso J. Schulz G. Öhrwall M. Lundwall T. Rander A. Lindblad H. Bergersen W. Pokapanich S. Svensson S. L. Sorensen N. Mårtensson O. Björneholm 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):295-299
Synchrotron-based X-ray photoelectron spectroscopy on copper and silver
cluster beams created by a magnetron-based gas-aggregation source has
allowed mapping the electron density of states (DOS) of free metallic
nanoparticles. The cluster DOS profiles obtained in the experiments strongly
resemble the infinite solid DOS shapes, but the extracted cluster
work-functions are lower than those for the bulk metal. The latter
observation is explained by the initial negative charge on most of the
clusters, created by the source. 相似文献
14.
I. Vilfan 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(2):277-284
The properties of
nanowires were investigated with
ab initio calculations based on the density-functional theory.
The molecules build weakly coupled one-dimensional chains, like
and Mo6S9-xIx, and the crystals are
strongly uniaxial in their mechanical and electronic properties.
The calculated moduli of elasticity and resilience along the chain axis are
c11 = 320 GPa and ER = 0.53 GPa, respectively.
The electronic band structure and optical conductivity indicate
that the
crystals are good quasi-one-dimensional conductors.
The frequency-dependent complex dielectric tensor ε, calculated
in the random-phase approximation, shows a strong Drude peak in
ε∥, i.e., for the electric field polarised parallel to
the chain axis, and several peaks related to interband transitions.
The electron energy loss spectrum is weakly anisotropic and has a strong peak
at the plasma frequency ħωp ≈20 eV.
The stability analysis shows that
is metastable against the
formation of the layered
. 相似文献
15.
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
RID="a"
ID="a"e-mail: ppiquini@smail.ufsm.br 相似文献
16.
Q. Sun Q. Wang X.G. Gong V. Kumar Y. Kawazoe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):77-81
We report results of the atomic and electronic structures of Al7C cluster using ab initio molecular dynamics with ultrasoft pseudopotentials and generalized gradient approximation. The lowest energy structure is
found to be the one in which carbon atom occupies an interstitial position in Al7 cluster. The electronic structure shows that the recent observation [Chem. Phys. Lett. 316, 31 (2000)] of magic behavior of Al7C- cluster is due to a large highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gap which makes Al7C- chemically inert. These results have further led us to the finding of a new neutral magic cluster Al7N which has the same number of valence electrons as in Al7C- and a large HOMO-LUMO gap of 1.99 eV. Further, calculations have been carried out on (Al7N)2 to study interaction between magic clusters.
Received 28 July 2001 相似文献
17.
E. S. Dy H. Kasai 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):241-245
We study the interaction between tin(II) porphyrin (SnPor) with platinum and
non-precious Group 8B metals (iron, cobalt and nickel) by density functional
theory and discuss the electronic properties of the resulting products. We
also model the interaction of the resulting compounds with water where
applicable. Our studies indicate that, SnPor-Ni possesses electronic
properties similar to SnPor-Pt, suggesting that it may possess similar
photocatalytic properties for reduction reactions, such as converting water
to hydrogen gas. 相似文献
18.
F. Aguilera-Granja A. Vega J. Rogan W. Orellana G. García 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(1):125-131
We report a comparative study of the magnetic properties of
free-standing PdN clusters (2 ≤N ≤21) obtained
through two different theoretical approaches that are extensively
employed in electronic structure calculations: a semi-empirical
Tight-Binding (TB) model and an ab-initio DFT pseudopotential
model. Conclusions are drawn about the reliability of the TB model for
the investigation of the electronic structure and magnetic properties
of such complex 4d Transition Metals (TM) systems and we compare the
results with previous systematic DFT calculations and comment on some
available experiments in the literature. 相似文献
19.
M.N. Huda A.K. Ray 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(2):217-227
The formalisms of many body perturbation theory and coupled cluster theory have been used to study the electronic and geometric
structures of neutral, cationic, and anionic small silver clusters. Hay-Wadt relativistic effective core potentials replacing
the twenty-eight core electrons and a Gaussian basis set have been used. Topologically different clusters and clusters belonging
to different symmetry groups have been identified and studied in detail. Full geometry optimizations have been carried out
at four different correlated levels of theories. Ionization potentials, electron affinities, and fragmentation energies of
the optimized clusters have been compared with other experimental and theoretical results available in the literature. No
convergence problems are encountered at the various levels of correlated theories. This is noteworthy since it has been claimed
in the literature that for d elements the MP series does not converge very well.
Received 16 April 2002 / Received in final form 12 September 2002 Published online 21 January 2003
RID="a"
ID="a"e-mail: akr@uta.edu 相似文献
20.
T. Kodaira S. Inoue Y. Murakami 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):267-270
Arrayed cationic K clusters including one 4s-electron in each cluster, i.e., Km+1
m+, were incorporated into α-cages of zeolite LTA with Si/Al=1.5. Although no magnetic phase transition was observed regarding
the temperature (T) dependence of magnetic susceptibilities originating from the 4s-electron spins (χspin) between 2 and 300 K, the χspin-T curve could be fitted by the sum of magnetic susceptibilities based on the Curie-Weiss law and Pauli paramagnetism. A possible
explanation of this behavior is the existence of a narrow energy band formed out of 1s-cluster orbitals of arrayed K clusters,
and the existence of a finite density of state at the Fermi energy. 相似文献