共查询到20条相似文献,搜索用时 29 毫秒
1.
Y. Dong M. Springborg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):15-18
The geometries and electronic properties of the most stable small
Aun clusters with n=2 to 20 are presented.
An intensive search for low-energy minima of Aun clusters was carried
through using a density-functional tight-binding method combined with genetic algorithms for an unbiased global structure
optimization. The structural and energetic properties of the small gold clusters are compared with those of planar Aun clusters with n=5 to 15. 相似文献
2.
Structural and electronic properties of Bin (n = 2-14) clusters from density-functional calculations
J. M. Jia G. B. Chen D. N. Shi B. L. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(3):359-365
The structural and electronic properties of Bin
(n = 2-14) clusters have been systematically studied using gradient-corrected
density-functional theory. For each cluster size, a number of structural
isomers were constructed and optimized to search for the lowest-energy
structure. The competition of several structural patterns such as cages,
superclusters, and layered structures leads to the alternating appearance of
these configurations as global minima. Although the tendency of Bi to form
puckered-layer structures is already well-known, the electronic states of
Bin clusters are still far from that of the bulk. As well, a remarkable
even-odd atom number oscillation is observed in the structural and
electronic properties of the clusters, implying that the stability of
Bin clusters is mainly dominated by the electron shell effect rather
than by geometrical packing. The theoretically calculated values for
electron affinities agree well with available experimental data. 相似文献
3.
M. R. Beltrán R. Suárez Raspopov G. González 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,65(3):411-420
We have explored lowest energy minima structures of gold atom clusters both, charged and
neutral (Au\hbox{nn_{n}^{\nu}}νn
with n = 20, 28, 34, 38, 55, 75, 101, 146, 147, 192, 212 atoms and
ν = 0, ±1). The structures have been obtained from
first principles generalized gradient approximation, density functional theory (DFT)
calculations based on norm-conserving pseudopotentials and numerical atomic basis sets. We
have found two new disordered or defective isomers lower in energy than their ordered
counterparts for n = 101, 147. The purpose of this work is to
systematically study the difference between the electronic properties of the two lowest
ordered and disordered isomers for each size. Our results agree with previous first
principle calculations and with some recent experimental results (Au20 and
Au101). For each case we report total energies, binding energies, ionization
potentials, electron affinities, density of states, highest occupied molecular
orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps, Housdorff chirality measure
index and their simulated image in a high resolution transmission electron microscopy
(HRTEM). The calculated properties of the two low lying (ordered and disordered) isomers
show clear differences as to be singled out in a suitable experimental setting. An
extensive discussion on the evolution with size of the cohesive energy, the ionization
potentials, the electron affinities, the HOMO-LUMO gaps and their index of chirality to
determine the crossover between them is given. 相似文献
4.
M. Vogel K. Hansen A. Herlert L. Schweikhard 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):73-76
The decay pathway competition between monomer and dimer evaporation of photoexcited cluster ions Au
+
n, n = 2-27, has been investigated by photodissociation of size-selected gold clusters stored in a Penning trap. For n > 6 the two decay pathways are distinguished by their experimental signature in time-resolved measurements of the dissociation.
For the smaller clusters, simple fragment spectra were used. As in the case of the other copper-group elements, even-numbered
gold cluster ions decay exclusively by monomer evaporation, irrespective of their size. For small odd-size gold clusters,
dimer evaporation is a competitive alternative, and the smaller the odd-sized clusters, the more likely they decay by dimer
evaporation. In this respect, Au
+
9 shows an anomalous behavior, as it is less likely to evaporate dimers than its two odd-numbered neighbors, Au
+
7 and Au
+
11. This nonamer anomaly is typical for copper-group cluster ions M
+
9 (M = Cu, Ag, Au) and a similar behavior is found in the anionic heptamers M
-
7. It is discussed in terms of the well-known electronic shell closing at n
e = 8 atomic valence electrons.
Received 2 November 2000 相似文献
5.
The equilibrium geometries and electronic properties of AunAl,
up to n=13, have been systematically investigated using the density
functional theory. The results show that, for the AunAl
clusters, two patterns are identified. Pattern one (n=2, 3, 8),
the lowest-energy geometries prefer two-dimensional structures.
Pattern two (n=4-7, 9--13), the lowest-energy geometries prefer
three-dimensional structures. According to the analysis of the
binding energy and the fragmentation energy, AunAl clusters
with odd n are found to be more stable than those with even n.
The same trend of alternation can be illuminated according to the
computational results in the HOMO--LUMO gap, the ionization
potential, and the electron affinities. The Al atom not only changes
the structures of pure gold clusters, but also enhances their
stabilities. NBO analysis indicates 6s orbital of Au atom hybridizes
with 3p orbital of Al atom. 相似文献
6.
Ligand-protected gold clusters are widely used in biosensors and catalysis. Understanding the structural evolution of these kinds of nanoclusters is important for experimental synthesis. Herein, based on the particle swarm optimisation algorithm and density functional theory method, we use [Au1(SH)2]n, [Au2(SH)3]n, [Au3(SH)4]n (n?=?1–3) as basic units to research the structural evolution relationships from building blocks to the final whole structures. Results show that there is a ‘line-ring-core’ structural evolution pattern in the growth process of the nanoclusters. The core structures of the ligand-protected gold clusters consist of Au3, Au4, Au6 and Au7 atoms. The electronics and optics analysis reflects that stability and optical properties gradually enhance with increase in size. These results can be used to understand the initial growth stage and design new ligand-protected nanoclusters. 相似文献
7.
The possible stable geometrical configurations and the relative stabilities of the lowest-lying isomers of copper-doped gold clusters,Au n Cu (n=1-7),are investigated using the density functional theory.Several low-lying isomers are determined.The results indicate that the ground-state Au n Cu clusters have planar structures for n=1-7.The stability trend of the Au n Cu clusters (n=1-7),shows that odd-numbered Au n Cu clusters are more stable than the neighbouring even-numbered ones,thereby indicating the Au 5 Cu clusters are magic cluster with high chemical stability. 相似文献
8.
F. Calvo E. Yurtsever 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(1):81-91
Finite-size effects on the static and thermodynamical
properties of small three-dimensional clusters of identical charged
particles confined by an harmonic trap are investigated using global
optimization and numerical simulations. The relative stabilities of
clusters containing up to 100 particles are estimated from the
second energy derivatives, as well as from the energy gap between
the two lowest-energy structures at a given size. We also provide a
lower bound for the number of permutationally independent minima, as
a function of size, up to n=75. Molecular dynamics and exchange
Monte Carlo simulations are performed to get insight into the finite
temperature behaviour of these clusters. By focusing on specific
sizes, we illustrate the interplay between the stable structures,
the possible competition between different isomers, and the melting
point. In particular, we find that the orientational melting
phenomenon known in two-dimensional clusters has an equivalent form
in some three-dimensional clusters. The vibrational spectra,
computed for all sizes up to 100, shows an increasing number of
low-frequency modes, but comparing to hydrodynamical theory reveals
strong correlation effects. Finally, we investigate the effects
of the trap anisotropy on the general shape of Coulomb clusters, and
on the melting point of a selected case. 相似文献
9.
D. Cheng S. Huang W. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(1):41-48
We have investigated segregation phenomena in Cu–Au
bimetallic clusters with decahedral structures at 100 K and 300 K, based on
the second-moment approximation of the tight-binding (TB-SMA) potentials by
using Monte Carlo method. The simulation results indicate that there are
three regions (split, three-shell onion-like and core-shell region) at 100 K
and two regions (split and core-shell) at 300 K with the structure of
decahedral clusters, as the chemical potential difference Δμ
changes. It is found that the structure of decahedral clusters undergoes a
division into smaller clusters in the split region. In the core-shell
structure, Au atoms are enriched in surface and Cu atoms occupy the core of
the clusters because of the different surface energy of Cu and Au. The Au
atoms are enriched in the surface shell, and the Cu atoms are in the middle
shell, while a single Au atom is located in the center to form the
three-shell onion-like structure. The structure and binding energy of
smaller clusters after splitting are also discussed. The Au atoms generally
lie on the surface of the smaller clusters after splitting. 相似文献
10.
An all-electron scalar relativistic calculation on AunH2S (n = 1-13) clusters has been performed by using density functional theory with the generalized gradient approximation at PW91 level. The small gold cluster would like to bond with sulfur in the same plane and the H2S molecule prefers to occupy the on-top and single fold coordination site in the cluster. The Aun structures and H2S molecule in all AunH2S clusters are only slightly perturbed and still maintain their structural integrity. After adsorption, the S-H, H-H bond-lengths and most Au-Au bond-lengths are elongated, only a few Au-Au bond-lengths far from H2S molecule are shortened. The reactivity enhancement of H2S molecule is obvious and the strong gold-sulfur bond is observed expectedly. The most favorable adsorption takes place in the case that the H2S molecule is adsorbed by an even-numbered Aun cluster and becomes AunH2S cluster with even number of valence electrons. It is believed that the strong scalar relativistic effect is favorable to H2S molecule adsorption onto small gold clusters and is also one of the important reasons for the strong gold-sulfur bond. 相似文献
11.
Density-functional method PW91 has been selected to investigate the structural, electronic and magnetic properties of Au4M (M =Sc–Zn) clusters. Geometry optimisations show that the M atoms in the ground-state Au4M clusters favour the most highly coordinated position. The ground-state Au4M clusters possess a solid structure for M = Sc and Ti and a planar structure for M = V–Zn. The characteristic frequency of the doped clusters is much greater than that of pure gold cluster. The relative stability and chemical activity are analysed by means of the averaged binding energy and highest occupied molecular orbital and lowest unoccupied molecular orbital energy gap for the lowest energy Au4M clusters. It is found that the dopant atoms can enhance the thermal stability of the host cluster except for Zn atom. The Au4Ti, Au4Mn and Au4Zn clusters have relatively higher chemical stability. The vertical detachment energy, electron affinity and photoelectron spectrum are calculated and simulated theoretically for all the ground-state structures. The magnetism calculations reveal that the total magnetic moment of Au4M cluster is mainly localised on the M atom and vary from 0 to 5 μB by substituting an Au atom in Au5 cluster with different transition-metal atoms. 相似文献
12.
S. Varga K. Bolton H. Grönbeck A. Snis A. Rosén B. Fricke 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):29-32
We present recent theoretical results for the V3 and Au4 clusters. Calculations of the V3 doublet system indicate that the 6-311+G(d) basis set is sufficiently flexible to provide reliable minimum energy structures
and vibrational frequencies, that these structures and frequencies are insensitive to spin contamination of the wave function
when the BPW91 functional is used, and that changing to the B3LYP functional may result in very different structures and frequencies.
A computationally less expensive scalar relativistic treatment of Au4 clusters gives structural properties that are in good agreement with those obtained using a four-component method.
Received 30 November 2000 相似文献
13.
Geometrical, electronic, and magnetic properties of the Sc-doped gold clusters, AunSc (n=1-8), have been studied using the density-functional theory within the generalized gradient approximation. An extensive structural search shows that the Sc atom in low-energy AunSc isomers tends to occupy the most highly coordinated position. The substitution of a Sc atom for an Au atom in the Aun+1 cluster markedly changes the structure of the host cluster. Moreover, we confirm that the ground-state Au6Sc cluster has a distortion to a lower D2h symmetry. The relative stabilities and electronic properties of the lowest-energy AunSc clusters are analyzed based on the averaged binding energies, second-order energy differences, fragmentation energies, chemical hardnesses, and HOMO-LUMO gaps. It is found that the magic Au3Sc cluster can be perceived as a superatom with high chemical stability and its HOMO-LUMO gap is larger than that of the closed-shell Zr@Au14 cluster. The high symmetry and spin multiplicity of the Au3Sc and Au6Sc clusters are responsible for their large vertical ionization potential and electron affinity. The magnetism calculations indicate that the magnetic moment of the Sc atom in the ground-state AunSc (n=2-8) clusters gradually decreases for even n and is completely quenched for odd n. 相似文献
14.
Mao Ai-Jie Kuang Xiao-Yu Chen Gang Zhao Ya-Ru Li Yan-Fang Lu Peng 《Molecular physics》2013,111(11):1485-1494
The ab initio method based on density functional theory at the B3PW91 level has been applied to study the geometric, electronic, and magnetic properties of neutral and anionic Au n Pd (n?=?1–9) clusters. The results show that the most stable geometric structures adopt a three-dimensional structure for neutral Au7Pd and Au8Pd clusters, but for anionic clusters, no three-dimensional lowest-energy structures were obtained. The relative stabilities of neutral and anionic Au n Pd clusters were analysed by means of the dependent relationships between the binding energies per atom, the dissociation energies, the second-order difference of energies, the HOMO–LUMO energy gaps and the cluster size n, and a local odd–even alternation phenomenon was found. Natural population analysis indicates the sequential transfer from the Pd atom to the Au n frame in Au1,2,3,5Pd and Au2,3Pd? clusters, and from the Au n frame to the Pd atom in other clusters. Much to our surprise, irrespective of whether it is the total magnetic moment or the local magnetic moment, the magnetic moment presents an odd–even alternation phenomenon as a function of the cluster size n. The magnetic effects are mainly localized on the various atoms (Au or Pd) for different cluster size n. 相似文献
15.
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
16.
M. Vogel K. Hansen A. Herlert L. Schweikhard 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(2):163-166
The dimer dissociation energies of gold cluster ions Au
+
n
, n
= 9, 11, 13, 15 have been determined with an extension of a recently developed model-independent method. Monomer-dimer decay
pathway branching ratios provide the energy dependent process which is needed in this method. The measured values are D
2
(
Au
+
9
) = 3.66(8)(9) eV, D
2
(
Au
+
11
) = 4.27(11)(8) eV, D
2
(
Au
+
13
) = 4.50(9)(7) eV and D
2
(
Au
+
15
) = 4.29(10)(6) eV.
Received 13 May 2002 / Received in final form 22 July 2002 Published online 24 September 2002
RID="a"
ID="a"e-mail: manuel.vogel@uni-mainz.de 相似文献
17.
S. F. Chekmarev R. Mitri V. Bonaci-Koutecký 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):45-48
The ab initio molecular
dynamics (AIMD) [1] is combined with the heuristic, successive
confinement method of surveying a potential energy surface (PES)
[2], thereby offering a framework for the simulation study of
kinetics and equilibrium properties of metallic clusters. This
approach is applied to the study of Au4,
a cluster possessing a simple but specific PES, which consists
of very shallow and deep basins and due to this presents a
challenge to the conventional AIMD methods. Among other things,
the probabilities of the transitions between isomers have been
found, and on this basis, both the time-dependent and
equilibrium populations of the isomers have been calculated for
the conditions typical of the NeNePo experiments [3] in the
femtosecond pump-probe spectroscopy. 相似文献
18.
V. Boutou A.R. Allouche F. Spiegelmann J. Chevaleyre M. Aubert Frécon 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(1):63-73
The geometrical structure of ground state Ban clusters (n
=2-14) has been predicted from various types of calculations including two ab initio approaches used for the smaller sizes namely HF+MP2(
n
=2-6), DFT (LSDA)(
n
=2-6, 9) and one model approach HF+pairwise dispersion used for all sizes investigated here. The lowest energy configurations
as well as some isomers have been investigated. The sizes n
=4, 7 and 13 are predicted to be the relatively more stable ones and they correspond to the three compact structures: the tetrahedron,
the pentagonal bipyramid and the icosahedron. The growth behavior from Ba7 to Ba13 appears to be characterized by the addition of atoms around a pentagonal bipyramid leading to the icosahedral structure of
Ba13 which is consistent with the observed size-distribution of barium clusters. Values for vertical ionization potentials calculated
for n
=2-5 at the CI level are seen to be in quite good agreement with recent measures.
Received: 14 May 1997 / Received in final form: 2 February 1998 / Accepted: 27 February 1998 相似文献
19.
M. X. Chen X. H. Yan S. Wei 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):513-517
Base on the density-functional theory, the structural and magnetic
properties of AunTi2
+ (
) clusters are investigated. The
two titanium atoms form a dimer in the gold clusters. The second-order
energy differences and HOMO-LUMO gap provide a clear explanation of the
abundance peaks and odd-even staggering observed recently in
photofragmentation experiments. The magnetism of AunTi2
+
cluster shows an odd-even effect when n increases from 1 to 4 and drops to
zero at n=5 and 7. The local magnetic moment and charge partition of Ti 4s,
3d orbitals are discussed. The peculiar magnetic properties are related to the
structures and the hybridization between the Au 5d, 6s states and Ti 3d, 4s
states. 相似文献
20.
M. Gaudry J. Lermé E. Cottancin M. Pellarin B. Prével M. Treilleux P. Mélinon J.-L. Rousset M. Broyer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):201-204
Optical properties of mixed clusters (AuxAg
1 - x
)
n
and (NixAg
1 - x
)
n
, produced by laser vaporization and embedded in an alumina matrix, are reported. The size effects are investigated for different
concentrations (x
= 0.25, 0.5 and 0.75) in the diameter range 2-4 nm. For alloyed clusters (AuxAg
1 - x
)
n
of a given size an almost linear evolution of the surface plasmon frequency ω
s
with the concentration is observed (between those of pure gold and pure silver clusters). Moreover the blue-shift and the
damping of the resonance with decreasing size is all the more important as the gold concentration in the particles increases.
Such results are in agreement with theoretical calculations carried out in the frame of the time-dependent local-density-approximation
(TDLDA) including an inner skin of ineffective screening and the porosity of the matrix. The optical response of (NixAg
1 - x
)
n
clusters exhibits a surface plasmon resonance in the same spectral range as the one observed for pure silver clusters, but
considerably damped and broadened. For a given mean cluster size 3.0 nm, a blue-shift of the resonance is observed when increasing
the nickel concentration (between x
= 0.25 and x
= 0.75). The results are in good qualitative agreement with classical predictions in the dipolar approximation, assuming a core-shell
geometry.
Received 21 November 2000 相似文献