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1.
The structure and the magnetic moment of transition metal encapsulated in a Au 12 cage cluster have been studied by using the density functional theory.The results show that all of the transition metal atoms(TMA) can embed into the Au 12 cage and increase the stability of the clusters except Mn.Half of them have the I h or O h symmetry.The curves of binding energy have oscillation characteristics when the extra-nuclear electrons increase;the reason for this may be the interaction between parity changes of extra-nuclear electrons and Au atoms.The curves of highest occupied molecular orbital-lowest unoccupied molecular orbital(HOMO-LUMO) gap also have oscillation characteristics when the extra-nuclear electrons increase.The binding energies of many M@Au 12 clusters are much larger than that of the pure Au 13 cluster,while the gaps of some of them are less than that of Au 13,so maybe Cr@Au 12,Nb@Au 12,and W@Au 12 clusters are most stable in fact.For magnetic calculations,some clusters are quenched totally,but the Au 13 cluster has the largest magnetic moment of 5 μ B.When the number of extra-nuclear electrons of the encapsulated TMA is even,the magnetic moment of relevant M@Au 12 cluster is even,and so are the odd ones. 相似文献
2.
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
3.
F.v. Gynz-Rekowski W. Quester R. Dietsche D. C. Lim N. Bertram T. Fischer G. Ganteför M. Schach P. Nielaba Y. D. Kim 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):409-413
The possibility of using magic Si7 clusters to form a cluster material was studied experimentally and theoretically. In experiments Si7 clusters were deposited on carbon surfaces, and the electronic structure and chemical properties of the deposited clusters
were measured using X-ray photoelectron spectroscopy (XPS). A non bulk-like electronic structure of Si7 was found in the Si 2p core level spectra. Si7 is suggested to form a more stable structure than the non-magic Si8 cluster and Si atoms upon deposition on carbon surfaces. Theoretically it was possible to study the interaction between the
clusters without the effect of a surface. Density functional theory (DFT) calculations of potential curves of two free Si7 clusters approaching each other in various orientations hint at the formation of cluster materials rather than the fusion
of clusters forming bulk-like structures. 相似文献
4.
High stability of the goldalloy fullerenes:A density functional theory investigation of M_(12)@Au_(20)(M=Na,Al,Ag,Sc,Y,La,Lu,and Au) clusters 下载免费PDF全文
Discovering highly stable metal fullerenes such as the celebrated C 60 is interesting in cluster science as they have potential applications as building blocks in new nanostructures.We here investigated the structural and electronic properties of the fullerenes M 12 @Au 20(M=Na,Al,Ag,Sc,Y,La,Lu,and Au),using a first-principles investigation with the density functional theory.It is found that these compound clusters possess a similar cage structure to the icosahedral Au 32 fullerene.La 12 @Au 20 is found to be particularly stable among these clusters.The binding energy of La 12 @Au 20 is 3.43 eV per atom,1.05 eV larger than that in Au 32.The highest occupied molecular orbital-lowest unoccupied molecular orbital(HOMO-LUMO) gap of La 12 @Au 20 is only 0.31 eV,suggesting that it should be relatively chemically reactive. 相似文献
5.
D. Cheng D. Cao 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(1):17-23
Canonical ensemble Monte Carlo simulations are applied to investigate the
melting of the icosahedral 55-atom Ag-Cu-Au clusters. The clusters are
modeled by the second-moment approximation of the tight-binding (TB-SMA)
many-body potentials. Results show that the introduction of the only Cu atom
of the third alloying metal in the bimetallic Ag43Au12 cluster,
forming the Ag42Cu1Au12 cluster, can greatly increase the
melting point of the cluster by about 100 K. It is also found that the
substitution of the only Cu atom of the third alloying metal in the
Ag1Au54 clusters, forming the Ag1Cu1Au53 cluster,
can result in an increase of 40 K in the melting point. It can be concluded
that the melting points of the bimetallic clusters can be tuned by the third
metal impurities doping. In addition, the surface segregation of Ag atoms in
the Ag-Cu-Au trimetallic clusters occurs even after melting. 相似文献
6.
采用基于密度泛函理论的第一性原理方法系统研究了Au与3d过渡元素构成的混合小团簇的结构、稳定性、电子结构及磁性,得到了Au与3d过渡元素构成的混合小团簇的稳定结构.计算结果表明,Au与3d元素可形成大量的低能异构体,特别是有些异构体在结构上极相近,这不同于共价或离子键类型的团簇.与纯过渡金属团簇类似,这类团簇也表现出复杂的磁性.过渡金属元素的磁矩相比体材料而言既有增强的、也有减弱的,与轨道的交换劈裂密切相关.对于基态构型,AuCr2,Au2Cr2关键词:
密度泛函理论
第一性原理方法
团簇
电子结构 相似文献
7.
Krati Joshi 《Molecular physics》2015,113(19-20):2980-2991
Finite-temperature behaviour of a hollow golden cage (HGC) plays a crucialrole in its potential applications as a catalyst, drug delivery agent, contrasting agent and so on. This physico-chemical property of HGCs is not well understood so far. In that context, Born–Oppenheimer molecular dynamics (BOMD) simulations are performed on a well-known ‘free-standing’ HGC. The cluster considered in this study is the ground state Au18 cluster (a cage with a diameter of about >5.5 Å). The results thus obtained are compared with the BOMD simulation results reported earlier on Au32 icosahedron cage, a conformation with a diameter of nearly. The sphericity of both the clusters is studied using a shape deformation parameter as a function of time and temperature. These results are supplemented by radial distribution function at various temperatures. The observations and analysis of results indicate that, both the clusters retain an HGC conformation from 300 to 400 K, admitting structural fluxionality by the Au18 cluster. Remarkably, the Au18 cluster is able to maintain its hollowness and sphericity up to a high temperature of 1000 K. Underlying structural and electronic properties influencing the individualistic behaviour of cages are highlighted. Composition of the frontier molecular orbitals and the charge distribution play a crucial role in the finite-temperature behaviour of the Au cages. The conclusions are supplemented by supporting calculations on another degenerate ground state Au18 hollow cage and a well-known pyramidal Au18 cage at 300 and 400 K. 相似文献
8.
Y. Li Y. P. Cao Y. F. Li S. P. Shi X. Y. Kuang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2012,66(1):7
The ab initio method based on density functional theory at the PW91PW91 level has been employed to systematically study the
structures, stabilities, electronic, and magnetic properties of gold clusters with or without silicon/phosphorus doping. The
optimized geometries show that the most stable isomers for Au
n
Si2 and Au
n
P2 (n = 1–8) clusters prefer a three-dimensional structure when n = 2 and n = 3 upwards, respectively, and they can be viewed as grown from the already observed Au
n−1M2 (M = Si, P). The relative stabilities of calculated Au
n
M2 (M = Si, P) clusters have been analyzed through the atomic average binding energy, fragmentation energy, second-order difference
of energy, and HOMO-LUMO gap. A pronounced odd-even alternative phenomenon indicates that the clusters with even-numbered
valence electrons possess a higher stability than their neighboring ones. For both systems, natural population analysis reveals
that electronic properties of dopant atoms in the corresponding configuration are mainly related to s and p states. We also investigated magnetic effects of clusters as a function of cluster size, however, their oscillatory magnetic
moments were found to vary inversely to the fragmentation energy, second-order difference of energy, and HOMO-LUMO gap. 相似文献
9.
M. Zhang S. Chen Q. M. Deng L. M. He L. N. Zhao Y. H. Luo 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,58(1):117-123
The geometries and electronic properties of the 3p electrons atoms doped gold cluster: M@Au6 clusters (M=Al, Si, P, S, Cl, Ar) have been systematically investigated by using relativistic all-electron density functional
theory (VPSR) and scalar relativistic effective core potential Stuttgart/Dresden (SDD) basis. Generalized gradient approximation
in the Perdue-Burke-Ernzerhof (PBE) functional form is chosen for geometry optimization. A number of new isomers are obtained
for neutral M@Au6 clusters. Both PBE/VPSR and PBE/SDD methods give similar lowest energy structure of each M@Au6cluster. With the exception of Ar@Au6, all doped clusters show larger relative binding energies compared with pure Au7 cluster. It is found that all the ground-state structures of the M@Au6 clusters prefer the low symmetry structures, which is very different to the 3d transition-metal impurity doped Au6 clusters. Our results are in excellent agreement with available experiment data. 相似文献
10.
Alexander Y. Galashev 《Molecular physics》2013,111(23-24):2555-2568
This paper reports on a study of the stability of silicon clusters of intermediate size at a high temperature. The temperature dependence of the physicochemical properties of 60- and 73-atom silicon nanoparticles are investigated using the molecular dynamics method. The 73-atom particles have a crystal structure, a random atomic packing, and a packing formed by inserting a 13-atom icosahedron into a 60-atom fullerene. They are surrounded by a ‘coat’ from 60 atoms of hydrogen. The nanoassembled particle at the presence of a hydrogen ‘coat’ has the most stable number (close to four) of Si–Si bonds per atom. The structure and kinetic properties of a hollow single-layer fullerene-structured Si60 cluster are considered in the temperature range 10 K ≤ T ≤ 1760 K. Five series of calculations are conducted, with a simulation of several media inside and outside the Si60 cluster, specifically, the vacuum and interior spaces filled with 30 and 60 hydrogen atoms with and without the exterior hydrogen environment of 60 atoms. Fullerene surrounded by a hydrogen ‘coat’ and containing 60 hydrogen atoms in the interior space has a higher stability. Such clusters have smaller self-diffusion coefficients at high temperatures. The fullerene stabilized with hydrogen is stable to the formation of linear atomic chains up to the temperatures 270–280 K. 相似文献
11.
X. J. Kuang X. Q. Wang G. B. Liu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,63(1):111-122
An all-electron scalar relativistic calculation on
Au
n
Pt (n = 1−12) clusters has been
performed by using density functional theory with the generalized gradient approximation
at PW91 level. Our results reveal that all the lowest energy geometries of
Au
n
Pt (n = 1−12) clusters may be
generated by substituting Pt atom for one gold atom of the
Au
n+1 cluster at the highest coordinated site. Compared with
corresponding pure Au
n+1 cluster, the lowest energy geometries
of Au
n
Pt clusters are distorted slightly and still keep the
planar structures due to the strong scalar relativistic effect in small gold cluster. The
Au-Pt bonds are stronger and most Au-Au bonds far from Pt atom are weaker than the
corresponding Au-Au bonds in pure Au
n+1 cluster. By
substituting Pt atom for one gold atom of Au
n+1 cluster at the
highest coordinated site, the relatively stable and inactive odd-numbered
Au
n+1 cluster becomes the relatively unstable and reactive
odd-numbered Au
n
Pt cluster, and the relatively unstable and
reactive even-numbered Au
n+1 cluster becomes the relatively
stable and inactive even-numbered Au
n
Pt cluster chemically
and electronically. All the Au
n
Pt clusters prefer low spin
multiplicity. The even-numbered Au
n
Pt clusters are found to
exhibit zero magnetic moment and the odd-numbered
Au
n
Pt clusters are found to possess magnetic moment with the
value of 1 μ
B. The odd-even alterations of magnetic moments
and electronic configurations for Au
n
Pt clusters are very
obvious and may be simply understood in terms of the electron pairing effect. 相似文献
12.
To model the adsorption of Au+ cation in aqueous solution on the semiconductor surface, the interactions of Au+ and hydrated Au+ cations with clean Si(1 1 1) surface were investigated by using hybrid density functional theory (B3LYP) and Møller-Plesset second-order perturbation (MP2) methods. Si(1 1 1) surface was described with Si7H11, Si11H17 and Si22H21 clusters. The effect of the basis set superposition error (BSSE) was taken into account by applying the counterpoise correction. The calculated results indicated that the binding energies between hydrated Au+ cations and clean Si(1 1 1) surface are large, suggesting a strong interaction between hydrated Au+ cations and the semiconductor surface. The bonding nature of the chemical adsorption of Au+ to Si surface can be classified as partial covalent as well as ionic bonding. As the number of water molecules increases, the water molecules form hydrogen bond network with one another and only one water molecule binds directly to the Au+ cation. The Au+ cation in aqueous solution will safely attach to the clean Si(1 1 1) surface. 相似文献
13.
The configurations, stability, and electronic structure of AuSin (n=1-16) clusters have been investigated within the framework of the density functional theory at the B3PW91/LanL2DZ and PW91/DNP levels. The results show that the Au atom begins to occupy the interior site for cages as small as Si11 and for Si12 the Au atom completely falls into the interior site forming Au@Si12 cage. A relatively large embedding energy and small HOMO-LUMO gap are also found for this Au@Si12 structure indicating enhanced chemical activity and good electronic transfer properties. All these make Au@Si12 attractive for cluster-assembled materials. 相似文献
14.
We have applied density functional theory (DFT) calculations to study the structures, stabilities, electronic and magnetic properties of mono and multiply oxygenated Si60H60 fullerenes (Si60H60–2nOn, n = 1, 3, 6, 9, 10, 12, 18, 20, 21, 27 and 30). DFT results show that rearrangement between the closed [6,6] and [5,6] isomers of Si60H58O follows a two-step pathway involving an intermediate and two transition states. Preserving the C3 symmetry in the cage structure, extra epoxidation of Si60H60 has been accomplished. Based on our results, formation energies per oxygen atom for the multiple additions of oxygen atoms on Si60H60 cage are positive (endothermic character), and increase with the increasing of the number of oxygen atoms. In general, the oxygenation of Si60H60 cage leads to an increase in the electrophilicity of the Si60H60–2nOn oxides. The oxygenation of Si–Si bonds not only introduces a substantial broadening of the NMR pattern but also yield individual peaks, indicating different electrostatic environments of silicon nuclei in the Si60H60–2nOn oxides. 相似文献
15.
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
16.
《Physics letters. A》2006,359(6):718-722
The structural parameters of Au75Si25 alloy, pure Au, Al88Si12, Cu87Sn13, In98Al2 and Al93Ni7 alloys have been measured by X-ray diffractometer. It is found that there are subpeaks in the pair correlation functions in liquid Au75Si25 alloy. The addition of Si in liquid Au results in a decrease in both the correlation radius and the coordination number of the nearest atomic neighbors. The Au75Si25 alloy nearest atomic distance has a more stable dependence on temperature compared to In98Al2, Al93Ni7 and Cu87Sn13 alloys. The atomic density change of liquid Au75Si25 alloy is less dependent on temperature than the liquid Au and Al88Si12 alloy. The liquid metallic good glass former Au75Si25 alloy possesses a more stable liquid structure than that of poor glass formers, indicating the essential of the fragility of the superheated melts. 相似文献
17.
Equilibrium geometries, relative stabilities, and magnetic properties of small AunMn (n=1-8) clusters have been investigated using density functional theory at the PW91P86 level. It is found that Mn atoms in the ground state AunMn isomers tend to occupy the most highly coordinated position and the lowest energy structure of AunMn clusters with even n is similar to that of pure Aun+1 clusters, except for n=2. The substitution of Au atom in Aun+1 cluster by a Mn atom improves the stability of the host clusters. Maximum peaks are observed for AunMn clusters at n=2, 4 on the size dependence of second-order energy differences and fragmentation energies, implying that the two clusters possess relatively higher stability. The HOMO-LUMO energy gaps of the ground state AunMn clusters show a pronounced odd-even oscillation with the number of Au atoms, and the energy gap of Au2Mn cluster is the biggest among all the clusters. The magnetism calculations indicate that the total magnetic moment of AunMn cluster, which has a very large magnetic moment in comparison to the pure Aun+1 cluster, is mainly localized on Mn atom. 相似文献
18.
L. Bolotov N. Uchida T. Kanayama 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):271-274
We present results of scanning tunneling spectroscopy (STS) measurements of hydrogen-saturated silicon clusters islands formed
on Si(111)-( 7×7) surfaces. Nanometer-size islands of Si6H12 with a height of 0.2-4 nm were assembled with a scanning tunneling microscope (STM) using a tip-to-sample voltage larger
than 3 V. STS spectra of Si6H12 cluster islands show characteristic peaks originating in resonance tunneling through discrete states of the clusters. The
peak positions change little with island height, while the peak width shows a tendency of narrowing for the tall islands.
The peak narrowing is interpreted as increase of lifetime of electron trapped at the cluster states. The lifetime was as short
as 10-13 s resulting from interaction with the dangling bonds of surface atoms, which prevents charge accumulation at the cluster
islands.
Received 30 November 2000 相似文献
19.
We have employed ab initio molecular dynamics to investigate the stability of the smallest gold cages, namely Au16 and Au17, at finite temperatures. First, we obtain the ground state structure along with at least 50 distinct isomers for both the
clusters. This is followed by the finite temperature simulations of these clusters. Each cluster is maintained at 12 different
temperatures for a time period of at least 150 ps. Thus, the total simulation time is of the order of 2.4 ns for each cluster.
We observe that the cages are stable at least up to 850 K. Although both clusters melt around the same temperature, i.e. around
900 K, Au17 shows a peak in the heat capacity curve in contrast to the broad peak seen for Au16.
相似文献
20.
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