共查询到20条相似文献,搜索用时 15 毫秒
1.
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
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ID="a"e-mail: akr@uta.edu 相似文献
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V. Bonačić-Koutecký C. Bürgel L. Kronik A. E. Kuznetsov R. Mitrić 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):471-476
We present structural and optical properties of silver clusters Agn (n=2, 4, 6, 8) at two model support sites of MgO, stoichiometric MgO(100) and FS-center defect, based on density functional theory and embedded cluster model. Our results provide the mechanism responsible
for the absorption and emission patterns due to the specific interaction between the excitations
within the cluster and the support site which is strongly cluster size and structure dependent.
We propose Ag4 at stoichiometric site as well as Ag2, Ag4 and Ag6 at FS-center defects as good candidates for the emissive centers in the visible regime. 相似文献
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S. R. Bhattacharyya T. K. Chini D. Datta R. Hippler I. Shyjumon B. M. Smirnov 《Journal of Experimental and Theoretical Physics》2008,107(6):1009-1021
We analyze scanning electron microscopy measurements for structures formed in the deposition of solid silver clusters onto
a silicon(100) substrate and consider theoretical models of cluster evolution onto a surface as a result of diffusion and
formation of aggregates of merged clusters. Scanning electron microscopy (SEM) data are presented in addition to energy dispersive
X-ray spectrometry (EDX) measurements of the these films. Solid silver clusters are produced by a DC magnetron sputtering
source with a quadrupole filter for selection of cluster sizes (4.1 and 5.6 nm or 1900 and 5000 atoms per cluster in this
experiment); the energy of cluster deposition is 0.7 eV/atom. Rapid thermal annealing of the grown films allows analysis of
their behavior at high temperatures. The results exhibit formation of cluster aggregates via the diffusion of deposited solid
clusters along the surface; an aggregate consists of up to hundreds of individual clusters. This process is essentially described
by the diffusion-limited aggregation (DLA) model, and thus a grown porous film consists of cluster aggregates joined by bridges.
Subsequent annealing of this film leads to its melting at temperatures lower than to the melting point of bulk silver. Analysis
of evaporation of this film at higher temperatures gives a binding energy in bulk silver of ɛ0= (2.74 ± 0.03) eV/atom.
The text was submitted by the authors in English. 相似文献
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A. Modelli 《Applied Surface Science》1987,30(1-4):298-303
Experimental results are presented for the substrate current appearing in thin oxide metal-oxide-silicon capacitors with a shallow n/p junction beneath the gate when a positive gate voltage in the tunneling regime is applied. The analysis of the current-voltage characteristics shows that for an oxide voltage drop lower than about 5 V the substrate current is due to electron tunneling from the silicon valence band. The dispersion relation in the energy range extending 3 eV below the oxide conduction band is determined from the voltage dependence of the current in the direct tunneling regime. An effective mass of about 0.8me is found near the edge of the oxide conduction band, while for lower energies a strong decrease of the effective mass is observed. 相似文献
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T. Tabarin R. Antoine M. Broyer P. Dugourd 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,37(2):237-239
We report the observation of bare silver cluster cations
obtained by electrospray ionization from a solution containing a metal salt
and tryptophan. Multiple step collision-induced dissociation in a quadrupole
ion trap of Ag9+ is reported. 相似文献
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用紫外光电子能谱和同步辐射光电子能谱研究了Sm掺杂C60薄膜的价带电子结构.Sm的价电子大部分转移给C60,化学键以离子性为主.对于任何化学配比都没有观察到费米边,所以Sm富勒烯超导相在室温下为半导体性质.获得了很接近单相Sm2.75C60的样品在费米能级附近的电子态密度分布.固溶相的光电子发射与Sm2.75C60有明显区别.SmxC60关键词:
60的Sm填隙化合物')" href="#">C60的Sm填隙化合物
价带光电子能谱
电子结构 相似文献
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S. Hüfner 《Zeitschrift für Physik B Condensed Matter》1992,86(2):241-246
The valence band photoemission spectroscopy of metallic Ce systems is inspected with regard to the different models employed for the interpretation of the data. It is concluded, that contrary to general believe, in most systems higher lyingf-excitations within the 4f manifold are observed, and the observation of the Kondo resonance is difficult. 相似文献
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Experimental photoelectron spectra of a clean polycrystalline Mo surface excited by monochromatized Al K α X-rays are presented. The spectra are compared with valence bands obtained by UPS and by band structure calculations within the 5 eV region below the Mo Fermi level. All results mentioned above display peaks at 0.3, 1.7, 2.8 and 4 eV belowE F. The energy distribution of the valence band does not vary with photon energy and electron emission angle for the four different polycrystalline Mo surfaces compared. It is concluded that the four peaks representing the Mo valence band are predominantly of bulk origin. 相似文献
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Struzhkin VV Mao HK Lin JF Hemley RJ Tse JS Ma Y Hu MY Chow P Kao CC 《Physical review letters》2006,96(13):137402
We report measurements of the valence band width in compressed Ge determined from x-ray emission spectra below the Ge K edge. The width of the valence band does not show any pressure dependence in the semiconducting diamond-type structure of Ge below 10 GPa. On the other hand, in the metallic beta-Sn phase above 10 GPa the valence band width increases under compression. Density-functional calculations show an increasing valence band width under compression both in the semiconducting phase (contrary to experiment) and in the metallic beta-Sn phase of Ge (in agreement with observed pressure-induced broadening). The pressure-independent valence band width in the semiconducting phase of Ge appears to require theoretical advances beyond the density-functional theory or the GW approximation. 相似文献
18.
B. Zhu Y. X. Wang Z. Y. Pan D. Cheng M. Hou 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,57(2):219-226
The coalescence of Au13, Au55 and Au147 icosahedral clusters
encapsulated inside single walled carbon nanotubes (CNTs) of different
diameters are investigated using molecular dynamics simulation with
semi-empirical potentials. Three steps needed for the formation of
encapsulated nanowires are followed in detail, namely, the penetration of
clusters in CNTs, the coalescence between two clusters inside CNTs and their
accumulation to form wires. It is suggested that no significant energy
barrier is encountered during the penetration of free clusters into CNTs
provided the CNT radius is large enough, that is, about 0.3 nm larger than
the cluster radius. The relative orientation of clusters imposed by the CNT
favors their spontaneous coalescence. After coalescence of two clusters, the
Au atoms are rearranged to form new structures of cylindrical symmetry that
may be seven fold, six fold, five fold, helical or fcc depending on the CNT
diameter. The thermal stability of these structures is discussed and the
structural properties of nanowires formed by accumulation of many clusters
in CNTs are analyzed in detail. A geometrical method is presented which
allows the prediction of the structure of multi-shell helical wires, when
knowing only the CNT radius.
These modeling results suggest the possibility of synthesizing metallic
nanowires with controlled diameter and structure by embedding clusters into
nanotubes with suitable diameters. 相似文献
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