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1.
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   

2.
The stuffed fullerene structures of medium-sized SiN ( ) clusters have been systemically studied using the all-electron density functional theory with gradient correction. For each cluster size, fullerene cages with different topologies and filled by different number of atoms were constructed and optimized to find the lowest-energy structure. The core atoms filled in the fullerene cages tend to form cage-like structures that resemble structural character of bulk diamond fragments. The size-dependent physical properties such as binding energies, electronic gaps, and ionization potentials have been discussed. Si45 exhibits relatively higher stability that can be associated with the low chemical reactivity observed by experiment.  相似文献   

3.
The soft deposition of Ni13 and Cu13 clusters on Ni(111) and Cu(111) surfaces is studied by means of constant-energy molecular-dynamics simulations. The atomic interactions are described by the Embedded Atom Method. It is shown that the shape of the nickel clusters deposited on Cu(111) surfaces remains rather intact, while the copper clusters impacting on Ni(111) surfaces collapse forming double and triple layered products. Furthermore, it is found that for an impact energy of 0.5 eV/atom the structures of all investigated clusters show the lowest similarity to the original structures, except for the case of nickel clusters deposited on a Cu(111) surface. Finally, it is demonstrated that when cluster and substrate are of different materials, it is possible to control whether the deposition results in largely intact clusters on the substrate or in a spreading of the clusters. This separation into hard and soft clusters can be related to the relative cohesive energy of the crystalline materials.  相似文献   

4.
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   

5.
Density-functional theory with generalized gradient approximation for the exchange-correlation potential has been used to calculate the structural and electronic properties of Si n C n (n = 10–15) clusters. We find that the Si n C n clusters prefer cagelike structures. An extensive isomer search shows that the lowest-energy arrangements are those in which the silicon atoms and the carbon atoms form two distinct subunits. It is found that the carbon atoms favor to form fullerene-like structure due to the sp 2-like bond. The silicon atoms are trying to cope with an unfavorable sp 2 environment, but distorted tetrahedra still show up somewhere of the cagelike structures. On the basis of the lowest-energy geometries obtained, the binding energy, HOMO–LUMO gap, Mulliken charge, ionization potential and electron affinity of the clusters have been computed and analyzed. An electronic charge transfer from the Si-populated to the C-populated regions is observed.  相似文献   

6.
The electronic structure and especially the band gap of Sin clusters (n=3–45 atoms) is studied by photoelectron spectroscopy. Contrary to expectations of quantum confinement, almost all clusters studied here have a band gap smaller than that of crystalline Si or even display a continuous (metallic) density of states. We attribute this to covalent bond formation analogous to the reconstructions observed on single-crystal surfaces. Additionally, for Si30 and Si33 a gap size of 0.6 eV (0.4 eV) is observed, supporting the prediction of stable, spherically symmetric structures of these particular clusters. Received: 18 November 1999 / Accepted: 24 November 1999 / Published online: 5 April 2000  相似文献   

7.
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   

8.
SiC is a highly stable material in bulk. On the other hand, alloys of silicon and carbon at nanoscale length are interesting from both technological as well fundamental view point and are being currently synthesized by various experimental groups (Truong et. al., 2015 [26]). In the present work, we identify a well-known silicon cluster viz., Si10 and dope it sequentially with carbon atoms. The evolution of electronic structure (spin state and the structural properties) on doping, the charge redistribution and structural properties are analyzed. It is interesting to note that the ground state SiC clusters prefer to be in the lowest spin state. Further, it is seen that carbon atoms are the electron rich centres while silicon atoms are electron deficient in every SiC alloy cluster. The carbon–carbon bond lengths in alloy clusters are equivalent to those seen in fullerene molecules. Interestingly, the carbon atoms tend to aggregate together with silicon atoms surrounding them by donating the charge. As a consequence, very few Si–Si bonds are noted with increasing concentrations of C atoms in a SiC alloy. Physical and chemical stability of doped clusters is studied by carrying out finite temperature behaviour and adsorbing O2 molecule on Si9C and Si8C2 clusters, respectively.  相似文献   

9.
We have studied the atomic structure and the electronic properties of Ban clusters by the ab initio molecular dynamics method. We find that a structural transition to the bulk-like structure begins at Ba9 cluster, and the structures of the clusters are transferred to be icosahedral-like around n = 13. The relatively high stability for Ba4, Ba10 and Ba13 clusters are observed. Received 1st December 2000  相似文献   

10.
First-principles studies are performed on Au12W@Si60 by using projector-augmented wave (PAW) method and generalized gradient approximation for the exchange-correlation energy. The geometry, electronic structure, orbital hybridization, and charge transfer are discussed. It is found that the magic Au12W cluster interacts strongly with Si, thus stabilizes Si60 cage structure. Meanwhile the metal cluster is dissociated when encapsulated in the Si60 cage, and charges are transferred from the Si cage to the metal atoms.Received: 30 December 2003, Published online: 17 February 2004PACS: 61.48. + c Fullerenes and fullerene-related materials - 36.40.Cg Electronic and magnetic properties of clusters - 61.46. + w Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals - 71.20.Tx Fullerenes and related materials; intercalation compounds  相似文献   

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