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1.
We investigate the configurations, electronic structures, and magnetic ordering of MnN (N = 2-13) clusters based on all-electron density functional theory. The Jahn-Teller effect plays an important role in determining the ground state of certain geometries. The magnetic ordering of the MnN dusters transits from ferromagnetic ordering for the smallest ( N = 2, 3) dusters to a near degeneracy state including ferromagnetic and ferrimagnetic ordering in the vicinity of N = 4-6 and to a clear ferrimagnetic ordering at N = 7 or beyond. N = 6 and 10 are the magic numbers for neutrai MnN (N = 2-13) dusters. 相似文献
2.
Mireille Leleyter Pierre Joyes Marie-Claire Cadeville 《Journal of Physics and Chemistry of Solids》1983,44(8):779-787
The intensities of emission of NipCn+(p = 1–3) and NiCn? secondary ions given by two alloys: Ni3C and NiC 5% at. C, show off a saw-toothed behaviour according to the parity of the number n of carbon atoms. Maxima occur when n is odd for NiCn+ ions and when n is even in the other cases (p = 2, 3; negative ions). Besides, the influence of the carbon concentration in the alloy can be observed.The alternations of NiCn+ and Ni2Cn+ ions can be interpreted from Pitzer and Clementi model (the clusters are supposed to be linear). Thus it can be found greater stabilities for NiC2k+1 and Ni2C2k chains than for NiC2k and Ni2C2k+1 chains respectively, which very well agrees with the “correspondence rule” between the emissions of different species of ions and their electronic properties. 相似文献
3.
The emission yields of the secondary ions are measured by using a conventional time of flight (TOF) technique under bombardments of Mg and C2, Ni and Si2 with different energies, and Cn, Sin and Nin (n = 1-3) with the different charge states and with energy of 1.5 MeV per atom, respectively. For the bombardments of Cn, Sin and Nin, the enhancements of the secondary ion emissions increase with increasing cluster sizes and charge states. For the bombardments of Mg and C2, Ni and Si2, although the mass and the nuclear charges of C2 and Si2 are the same as or equivalent to Mg or Ni, respectively, the enhancements of the secondary ion emissions induced by the clusters of C2 and Si2 in a wide energy range are also clearly indicated. The instantaneous collective interaction of the cluster constituents plays an important role in the secondary ion emissions. 相似文献
4.
ABSTRACTHydrogen storage reactions on Ni ? C59X(X = B, N) heterofullerene are investigated by using the state-of-the-art density functional theory calculations. The Ni atom prefers to bind at the bridge site between two hexagonal rings, and can bind up to five hydrogen molecules with average adsorption energies of (?0.94, ?0.48, ?0.33, ?0.25 and ?0.20 eV) per hydrogen molecule for Ni ? C59B, while (?1.20, ?0.60, ?0.41, ?0.28 and ?0.23 eV) per hydrogen molecule for Ni ? C59N. With no metal clustering, the system gravimetric capacities are expected to be as large as 10.87 and 10.85 wt % for 5H2NiC59B?and 5H2NiC59N, respectively. While the desorption activation barriers of the complexes 1H2 + C59X?(X = B, N)?are outside the Department of Energy domain (?0.2 to ?0.6 eV), the desorption activation barriers of the complexes nH2 + C59X(X = B, N)(n = 2 ? 5) are inside this domain. The hydrogen storage of the irreversible 1H2 + NiC59X?(X = B, N) and reversible 2H2 + NiC59X?(X = B, N) interactions is characterised in terms of density of states and projected densities of states, pairwise and non-pairwise additivity, infrared, Raman, electrophilicity and molecular electrostatic potentials. 相似文献
5.
E. Cottancin M. Gaudry M. Pellarin J. Lermé L. Arnaud J. R. Huntzinger J. L. Vialle M. Treilleux P. Mélinon J.-L. Rousset M. Broyer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):111-114
The optical properties of mixed
(Ni0.5Ag0.5)n
and Pt/Ag clusters are investigated in the size range 2-5 nm.
Low Energy Ion Spectroscopy (LEIS) experiments show that the
cluster surface is entirely covered by silver atoms for the two
systems. The optical spectra of Ni/Ag clusters exhibit a large
Surface Plasmon Resonance (SPR), damped and widened when the
cluster size decreases, in agreement with a classical model
assuming a core-shell geometry and including the reduction of
the conduction electron mean-free path in the silver shell. For
Pt/Ag clusters, no SPR emerges in the size range 2-5 nm,
although it is predicted within a classical model, a pronounced
SPR appearing only for clusters larger than 10 nm in diameter. 相似文献
6.
J. Wang J. Zhao L. Ma G. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):289-294
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
7.
An effective method of producing small neutral carbon dusters Cn (n = 1-6) is described. The small carbon dusters (positive or negative charge or neutral) are formed by plasma which are produced by a high power 532nm pulse laser ablating the surface of the metal Mn rod to react with small hydrocarbons supplied by a pulse valve, then the neutral carbon clusters are extracted and photo-ionized by another laser (266nm or 355nm) in the ionization region of a linear time-of-flight mass spectrometer. The distributions of the initial neutral carbon dusters are analysed with the ionic species appeared in mass spectra. It is observed that the yield of small carbon dusters with the present method is about 10 times than that of the traditional widely used technology of laser vaporization of graphite. 相似文献
8.
A phase field microelasticity simulation is performed to examine the antisite defect of L12-Ni3Al in Ni75Al5.3 V19.7 ternary alloy. Combinimg strain energy with the phase field model leads to an atom configuration change as time proceeds. For the Ni sublattice, the antisite defect AlNi, the equilibrium occupancy probability (OP) of which declines, precedes NiNi and VNi in reaching equilibrium; subsequently, NiNi and VNi present a phenomenon of symmetrical rise and decline individually. Similarly, for the Al sublattice, the antisite defect NiAl, the OP of which eventually rises, takes fewer time steps than AlAl and VAl to attain equilibrium. Thereafter, AlAl rises while VAl declines symmetrically at the axes of the NiAl curve. Furthermore, the OP for the Al sublattice is much more sensitive to strain energy than that for the Ni sublattice. 相似文献
9.
Adsorption of ordered (2×2) arrays of Nb4 clusters on the insulating surface of NaCl(100) is studied by the first-principles calculations within the density functional theory. The calculations on the relaxed geometries and cohesive energies show that both the tetrahedron and quadrangle-Nb4 can be stably adsorbed on this substrate, which may have important applications. The adsorption of quadrangle-Nb4 on the NaCl(100) surface is more stable than that of tetrahedron-Nb4. Both the Nb4 clusters studied and a single Nb atom prefer the top site of the Cl atom in the NaCl(100) surface. Electronic structure analysis suggests that the interactions between the Nb4 clusters and the substrate are weak 相似文献
10.
本文研究了Fe40Ni40P12B8非晶合金冲击波加载下的晶化行为,冲击波由二级轻气炮发射的告诉弹丸撞击靶产生。实验结果表明:Fe40Ni40P12B8非晶合金在冲击波加载下,晶化可在加载时间(微秒量级)内发生;晶化的阈值压力在30~50 GPa之间,相应的冲击温度约为510~800 K,晶化析出相与冲击压力有关,低压下析出相是面心立方γ-(Fe, Ni)固溶体和Fe3(P0.37B0.63)化合物,高压下(大于60 GPa)析出相除了面心立方γ-(Fe, Ni)固溶体和Fe3(P0.37B0.63)化合物之外,还包括(Fe, Ni)3P化合物。 相似文献
11.
Ternary transition metal nitrides, Fe3 W3N, Coa W3N, and Nia WaN~ are studied by the use of interatomic potentials acquired from lattice inversion. The study indicates that Fe3 WaN would be more stable than the other compounds in the family of intermetallic tungsten nitrides. The investigation of phonon density of states indi- cates that the lower frequency modes are mostly excited by the metal atoms, and the higher frequency modes are mostly excited by the nitrogen atoms. A qualitative analysis is carried out with the relevant potentials for the phase stability and vibrational modes. 相似文献
12.
I. L. Garzón M. R. Beltrán G. González I. Guterrez-González K. Michaelian J. A. Reyes-Nava J. I. Rodrguez-Hernández 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):105-109
Theoretical and experimental information on the shape and
morphology of bare and passivated gold clusters is fundamental
to predict and understand their electronic, optical, and other
physical and chemical properties. An effective theoretical
approach to determine the lowest-energy configuration (global
minimum) and the structures of low energy isomers (local minima)
of clusters is to combine genetic algorithms and many-body
potentials (to perform global structural optimizations), and
first-principles density functional theory (to confirm the
stability and energy ordering of the local minima). The main
trend emerging from structural optimizations of bare Au clusters
in the size range of 12-212 atoms indicates that many
topologically interesting low-symmetry, disordered structures
exist with energy near or below the lowest-energy ordered
isomer. For example, chiral structures have been obtained as the
lowest-energy isomers of bare Au28 and
Au55 clusters, whereas in the size-range
of 75-212 atoms, defective Marks decahedral structures are
nearly degenerate in energy with the ordered symmetrical
isomers. For methylthiol-passivated gold nanoclusters
[Au28(SCH3)16
and
Au38(SCH3)24],
density functional structural relaxations have shown that the
ligands are not only playing the role of passivating molecules,
but their effect is strong enough to distort the metal cluster
structure. In this work, a theoretical approach to characterize
and quantify chirality in clusters, based on the Hausdorff
chirality measure, is described. After calculating the index of
chirality in bare and passivated gold clusters, it is found that
the thiol monolayer induces or increases the degree of chirality
of the metallic core. We also report simulated high-resolution
transmission electron microscopy (HRTEM) images which show that
defects in decahedral gold nanoclusters, with size between 1-2
nm, can be detected using currently available experimental HRTEM
techniques. 相似文献
13.
K. Hashimoto M. Okamoto K. Takayanagi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(1):75-78
The stability of neutral, singly and multiply ionized silicon clusters, (N
= 2-7, M
= 0, , , ), has been investigated using an ab initio density functional method. We show that the fragmentation effect significantly affects the structure of mass-spectra of multiply
ionized silicon clusters. For clusters, the clusters with a large fragmentation energy are found to correspond to the high peaks at N = 4 and 6 in mass-spectra. For clusters, a peak at N = 5 in mass-spectra has been predicted to be especially high.
Received: 9 June 1997 / Revised: 8 January 1998 / Accepted: 25 February 1998 相似文献
14.
T.W Schmidt 《Journal of Molecular Spectroscopy》2003,222(1):86-92
Electronic spectra of a series of weakly bound clusters consisting of argon (Arn, n=1-4) bound to the butadiyne cation, C4H2+, have been recorded in the visible range from 440 to 520 nm by photodissociation. The C4H2+ fragment signal was recorded as a function of the laser wavelength during excitation of the A←X electronic transition. The observed transitions were assigned to the band origin of the cationic complexes and to vibronic bands involving excitation of the ν3 and ν7 vibrational modes of the C4H2+ moiety, as well as combination bands of these modes. Comparison of the photodissociation spectra of the various clusters reveals a small blue shift, 25 cm−1 of the band maxima relative to the corresponding transitions reported from gas phase spectra of the bare C4H2+ cation. The magnitude of the blue shift of each band increases with successive Ar solvation up to n=3. Furthermore, each band becomes increasingly broadened towards the red with the addition of Ar atoms due to an increasing number of unresolved transitions involving excited intermolecular modes. 相似文献
15.
U. Heiz 《Applied Physics A: Materials Science & Processing》1998,67(6):621-626
We report on the size-dependent chemical reactivity of nickel clusters with up to 30 atoms. Monodispersed Ni30 clusters show a higher reactivity for CO dissociation than Ni11 and Ni20. Under our experimental conditions the smallest nickel clusters (Nix, x<4) produce nickelcarbonyl complexes. These results demonstrate that such small clusters are unique for catalytic reactions
not only due to their high surface-to-volume ratio but also essentially because of the distinctive properties of different
cluster sizes. In addition thermal desorption spectroscopy of CO shows that on average four molecules are weakly adsorbed
per Ni11 at saturation coverage. Using an isotopic mixture of 12CO and 13CO, infrared spectroscopy reveals the existence of a vibrational coupling interaction between the four COs. A semi-classical
model of interacting dipoles is applied to correlate the observed vibrational frequency shifts with the arrangement of the
COs on the cluster. This simple analysis favors a three-dimensional structure for the deposited clusters.
Received: 23 March 1998/Accepted: 25 August 1998 相似文献
16.
Nitrogen-doped ZnO (ZnO:N) films are prepared by thermal oxidation of sputtered Zn3N2 layers on A1203 substrates. The correlation between the structural and optical properties of ZnO:N films and annealing temperatures is investigated. X-ray diffraction result demonstrates that the as-sputtered Zn3N2 films are transformed into ZnO:N films after annealing above 600℃. X-ray photoelectron spectroscopy reveals that nitrogen has two chemical states in the ZnO:N films: the No acceptor and the double donor (N2)o. Due to the No acceptor, the hole concentration in the film annealed at 700℃ is predicted to be highest, which is also confirmed by Hall effect measurement. In addition, the temperature dependent photoluminescence spectra allow to calculate the nitrogen acceptor binding energy. 相似文献
17.
基于第一性原理,用密度泛函理论中的广义梯度近似方法,获得了BnNi(n≤5)小团簇在不同自旋多重度下的几何构型,确定了最低能量结构,并计算了相应的频率、平均结合能和磁性. 结果表明:BnNi(n≤5)小团簇最低能量结构的自旋多重度分别为2,1,2,1,2;Ni掺入B团簇后增大了其结合能;Ni原子磁矩和团簇总磁矩随团簇尺寸增大而呈现振荡趋势.
关键词:
nNi小团簇')" href="#">BnNi小团簇
自旋多重度
磁性 相似文献
18.
A. Salmoun R. Brédy J. Bernard L. Chen S. Martin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(1):55-61
Electron capture processes in collision between slow
X7+ (X = N, O and Ne) ions and C60 fullerene have been
investigated using coincident measurements of the number n of ejected
electrons, the mass and charge of the multicharged C60
r+ recoil ions and their fragments Cm
i+ and the final charge state of the
outgoing projectiles X(q-s)+ (
). The
collision velocity is about 0.4 a.u. The partial cross-sections σr
s , corresponding to r electrons transferred to the projectile with only s electrons stabilized, have been measured. Cross-sections
for collisions “inside” and those “outside” the C60
cage have been separated by analyzing the kinetic energy of the outgoing
projectile. The mean final charge state for frontal collisions has been
measured to 3.1, 2.6 and 2.5 for N7+, O7+ and Ne7+
respectively. These results show the importance of the core effect on the
stabilisation processes of captured electrons. 相似文献
19.
Formation Mechanisms of Electrical Conductivity and Optical Properties of ZnO:N Film Produced by Annealing Treatment 下载免费PDF全文
WANG Xiang-Hu YAO Bin WEI Zhi-Peng SHEN De-Zhen ZHANG Zhen-Zhong LU You-Ming ZHANG Ji-Ying FAN Xi-Wu 《中国物理快报》2008,25(8):2993-2996
The effects of annealing on the chemical states of N dopant, electrical, and optical properties of N-doped ZnO film grown by molecular beam epitaxy (MBE) are investigated. Both the as-grown ZnO:N film and the film annealed in N2 are of n-type conductivity, whereas the conductivity converts into p-type conductivity for the film annealed in O2. We suggest that the transformation of conductivity is ascribed to the change in ratio of the N molecular number on O site (N2)O to the N atom number on O site (NO) in ZnO:N films under the various annealed atmosphere. For the ZnO:N film annealed in N2, the percentage content of (N2)O is larger than that of NO, i.e.the ratio >1, resulting in the n-type conductivity. However, in the case of the ZnO:N film annealed in O2, the percentage content of (N2)O is fewer than that of NO, i.e., the ratio <1, giving rise to the p-type conductivity. There is an obvious difference between low-temperature (80K) PL spectra of ZnO:N film annealed in N2 and that of ZnO:N film annealed in O2. An emission band located at 3.358eV is observed in the spectra of the ZnO:N film after annealed in N2, this emission band is due to donor-bound exciton (D0X). After annealed in O2, the PL of the donor-bound exciton disappeared, an emission band located at 3.348eV is observed, this emission band is assigned to acceptor-bound exciton (A0X). 相似文献
20.
M. Hedén M. Kjellberg A. V. Bulgakov K. Hansen E. E.B. Campbell 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):255-259
Molecular fusion is induced in clusters of fullerene molecules on excitation with fs laser pulses. The dependence of the mass
distributions of the fused products on the initial cluster distribution are studied and results for (C60)N and (C70)N clusters are compared. The fused products decay by emitting C2 molecules and the fragmentation spectrum is used to determine the initial excitation energy of the fused species. The threshold
excitation energy needed to induce fusion is consistent with the energetic thresholds for molecular fusion of fullerenes determined
previously in single collision experiments. 相似文献