共查询到20条相似文献,搜索用时 31 毫秒
1.
J. Akola A. Rytkönen H. Häkkinen M. Manninen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(1):93-99
The ionization potential of sodium clusters () at a finite temperature is studied using density functional theory and ab initio molecular dynamics. The threshold regions of the photoionization efficiency curves are deduced from the integrated IP distributions,
which are obtained from the energy eigenvalues of the highest occupied Kohn-Sham states during molecular dynamics by applying
a theoretically well-defined shift. The calculated ionization potentials are directly compared to the experimental values.
The energetically best geometry of Na55 is found to be a slightly distorted icosahedron.
Received 16 April 1999 and Received in final form 6 July 1999 相似文献
2.
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
3.
J. Zhao Y. Luo G. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):309-316
Tight-binding model is developed to study the structural and electronic properties of silver clusters. The ground state structures
of Ag clusters up to 21 atoms are optimized by molecular dynamics-based genetic algorithm. The results on small Agn clusters (n = 3-9) are comparable to ab initio calculations. The size dependence of electronic properties such as density of states, s-d band separation, HOMO-LUMO gap, and ionization potentials are discussed. Magic number behavior at Ag2, Ag8, Ag14, Ag18, Ag20 is obtained, in agreement with the prediction of electronic ellipsoid shell model. We suggest that both the electronic and
geometrical effect play significant role in the coinage metal clusters.
Received 7 August 2000 相似文献
4.
S. Neukermans N. Veldeman E. Janssens P. Lievens Z. Chen P.v.R. Schleyer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):301-308
We report a combined experimental and computational
investigation of small AlnOm species (n ≤20, m ≤
12), produced in a laser vaporization cluster source. The oxygen
content in the clusters was tuned by varying the oxygen
concentration in the carrier gas. Ionization energies are
bracketed using different ionizing photon energies in the energy
range between 5.37 and 7.89 eV. Among the singly doped AlnO
species, Al3O and Al15O are found to have relatively low
ionization energies, which can be related to the magic character
of the corresponding cations. Peculiarly low ionization energies
also are observed for specific oxygen rich species (m > 1),
suggesting the formation of ionically bound subunits. The
structures and ionization energies of singly doped AlnO0,+
(n = 1 - 7) clusters were determined using density functional
theory (B3LYP/6-311+G(d)).
Electronic supplementary material Supplementary Online Material 相似文献
5.
J.M. Mestdagh M. Berdah N. Auby C. Dedonder-Lardeux C. Jouvet S. Martrenchard-Barra D. Solgadi J.P. Visticot 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(3):291-302
The photodissociation of a chlorine molecule in the environment of a xenon cluster has been studied experimentally using the
real time pump and probe technique through the formation of an XeCl reaction product. The photodissociating system is probed
in such a way that the movement of a single chlorine atom in the xenon environment is detected. Various XenCl2 cluster sizes have been investigated leading to the distinction between uncapped, half-capped and doubly capped structures
for these clusters. These structures have a profound influence on the photodissociation dynamics. Retrapping of one chlorine
atomic fragment and stabilization of the XeCl reaction product is only observed for the half and doubly capped clusters. The
experimental work is complemented by classical molecular dynamics calculations to get a full picture of the photodissociation.
Received: 17 February 1998 / Received in final form and Accepted: 28 July 1998 相似文献
6.
P. Parneix 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):375-383
The isomerization and evaporation processes in the neutral homogeneous (CH3CN)n molecular clusters (n
= 2-7) have been investigated using classical molecular dynamics simulations. The evaporation rate constants and the kinetic energy
release in the dissociation have been analysed as a function of the cluster size and as a function of the internal energy
in the parent cluster. The competition between monomer and dimer ejections has been also carefully studied. All the dynamical
properties in these dissociative processes have been discussed in relation to the static properties of the clusters involved
in the dissociation and also in relation to the solid-liquid like transition which appears in these homogeneous molecular
clusters.
Received 19 November 2002 / Received in final form 5 February 2003 Published online 29 April 2003
RID="a"
ID="a"e-mail: pascal.parneix@ppm.u-psud.fr
RID="b"
ID="b"Laboratoire associé à l'université Paris-Sud. 相似文献
7.
G. Chen Z.F. Liu X.G. Gong 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):33-36
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
8.
M. Bertolus V. Brenner P. Millié 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(3):387-394
An ab initio study of the Nan(OH)n, Nan(OH)n-1
+, Agn(OH)n, and Agn(OH)n-1
+ clusters with n up to four is presented. The results of this study show that, in accordance with experimental observations, the sodium hydroxide
clusters are almost purely ionic, while the Ag-O bond exhibits a significant covalent character. The perturbation caused by
the non-spherical OH- group relatively to an atomic anion, as well as the influence on structures and energies of the covalent character of the
metal-oxygen bond are determined. The appearance of metal-metal bonds in the silver hydroxide clusters is also discussed.
Finally, the theoretical results obtained on the Na-OH clusters are compared to experimental results available on the dissociation
of the Nan(OH)n-1
+ clusters.
Received 9 August 1999 and Received in final form 1st December 1999 相似文献
9.
G.M. Koretsky M.B. Knickelbein 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(3):273-278
The photoionization spectra of Pr2-Pr21 and Ce2-Ce17 have been measured near threshold. The ionization potentials (IPs) of and vary discontinuously with size, but trend downward toward the work function of the bulk metals. In general, the IPs of cerium
clusters display more variation than those of praseodymium clusters. The sudden discontinuities observed in the IPs of both
and is akin to that displayed by clusters of transition metal atoms, suggesting that as in transition metal clusters, the rapid
evolution in geometric structure with size is the source of these discontinuities.
Received: 2 January 1998 / Accepted: 10 March 1998 相似文献
10.
A.M. Vichare D.G. Kanhere 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(1):89-94
Density based molecular dynamics has been used to investigate the ground state structures of heterogeneous binary clusters
Al13Lin, n
= 1, 2, 3, 4, 10, 19, 20, 21. Some of these structures have also been investigated by full Kohn-Sham based calculations. Our
earlier investigations have shown that in the Al-Li cluster, the ground state configurations are the ones where the Al atoms
form a core around which the Li atoms form a “cage”. In the present work, we have chosen the well-known Al13 icosahedron as the surface over which we study the evolution of the surface coverage as the number of Li atoms increases.
On the basis of the earlier work, we expect that the Al13Li20 cluster would be the most stable and indeed our simulations do yield such a novel fivefold symmetric stable structure formed
out of purely metal atoms. This icosahedral substrate is also used to study the coverage of the aluminum surface by lithium
atoms. For a small number of Li atoms, these studies suggest that the Li-Li dimerisation is not particularly favored.
Received: 24 October 1997 / Revised: 7 April 1998 / Accepted: 29 June 1998 相似文献
11.
A. Rytkönen M. Manninen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):351-357
The effect of melting transition on the ionization potential has been studied for sodium clusters with 40, 55, 142, and 147
atoms, using ab initio and classical molecular dynamics. Classical and ab initio simulations were performed to determine the ionization potential of Na142 and Na147 for solid, partly melted, and liquid structures. The results reveal no correlation between the vertical ionization potential
and the degree of surface disorder, melting, or the total energy of the cluster obtained with the ab initio method. However, in the case of 40 and 55 atom clusters, the ionization potential seems to decrease when the cluster melts.
Received 1st November 2002 Published online 24 April 2003
RID="a"
ID="a"e-mail: ar@phys.jyu.fi 相似文献
12.
C. Bréchignac Ph. Cahuzac B. Concina J. Leygnier I. Tignères 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):185-192
The cross-sections for collisional charge transfer between singly charged free clusters M
n
+ (M = Li, Na; n=1...50) and atomic targets A (cesium, potassium) have been measured as a function of collisional relative velocity in laboratory
energy range 1–10 keV. For each cluster size, the experimental values of the charge transfer cross-section are fitted with an universal parametric curve with two independent parameters and vm, the maximum cross-section and the corresponding velocity. For small size clusters (), the characteristic parameters show strong variations with the number of atoms in the cluster. Abrupt dips observed for n=10 and n=22 are attributed to electronic properties. Charge transfer patterns observed for various collisional systems present similarities,
which appear more sensitive to cluster quantum size effects than to collision energy defects. In their whole, the and vm parameters show differences in both their size evolution and their absolute values discussed in term of projectile and target
electronic structures.
Received 13 April 2000 and Received in final form 29 June 2000 相似文献
13.
A. Herlert L. Schweikhard M. Vogel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):65-68
Singly charged silver-cluster anions are produced in a laser vaporization source and transferred into a Penning trap. After
size selection the clusters are subjected to an electron bath in the trap, which results in the attachment of further electrons.
The relative abundance of dianions or trianions as a function of the clusters' size is analyzed by time-of-flight mass spectrometry.
Silver-cluster dianions are observed for sizes n≥ 24 and trianions for n > 100. In addition, a detailed study of the cluster sizes 24 ?n? 60 shows a pronounced resistance to electron attachment for singly charged anions Agn
- with a closed electronic shell, in particular Ag29
-, Ag33
-, and Ag39
-. Both the threshold size for the observation of dianionic silver clusters and the shell effects in the production yield correlate
favorably with previous theoretical investigations of the respective electron affinities.
Received 24 November 2000 相似文献
14.
G. Mattei F. Toigo 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,3(3):245-256
The effect of non-local norm-conserving pseudo-potentials on the static and dynamic properties of Nan and Lin cluster with n=6,8 is investigated in the frame of self-consistent LDA calculations with spherically averaged ionic density (SAPS model).
A comparison with previous calculations which use local pseudo-potentials as well with uniform averaged non-local pseudo-jellium
calculation has been carried out. A better quantitative agreement with experiments has been found in the calculation of the
photoresponse cross-section with respect to either simple jellium or pseudo-jellium model, even in very small clusters, where
deviations from sphericity are not negligible.
Received: 3 March 1998 / Received in final form and Accepted: 2 June 1998 相似文献
15.
P. Feiden J. Leygnier Ph. Cahuzac C. Bréchignac 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):49-52
Condensation of nano-droplets in a supersaturating vapor decomposes in two steps: the formation of a nucleation center, also
called critical nuclei or nucleation seed, and the growth sequence, by accretion of further atoms on the nucleation center.
These two steps have been investigated separately through the clustering of homogeneous particles Nan and heterogeneous particles NanX in a helium buffer gas (X = (Na2O)2 or (NaOH)2). The growth sequence is analyzed with preformed molecules X injected in a supersaturating sodium vapor and driving production
of NanX clusters.
Cluster distribution mean sizes are controlled by sodium concentration and by the condensation cell effective length. The
signal intensities observed for homogeneous and heterogeneous clusters are proportional to the homogeneous and heterogeneous
nucleation center numbers respectively. We can measure the efficiency for the homogeneous nucleation center production versus
sodium concentration. This process is the onset of the condensation phase transition. 相似文献
16.
Metastable fragmentation of silver bromide clusters 总被引:2,自引:0,他引:2
J.-M. L'Hermite F. Rabilloud L. Marcou P. Labastie 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):323-330
The abundance spectra and the fragmentation channels of silver bromide clusters have been measured and analyzed. The most
abundant species are AgnBrn - 1
+ and AgnBrn + 1
- and Ag14Br13
+ is a magic number, revealing their ionic nature. However, some features depart from what is generally observed for alkali-halide
ionic clusters. From a certain size, AgnBrn - 1
+ is no more the main series, and AgnBr n - 2, 3
+ series become almost as important. The fast fragmentation induced by a UV laser makes the cations lose more bromine than
silver ions and lead to more silver-rich clusters. Negative ions mass spectra contain also species with more silver atoms
than required by stoichiometry. We have investigated the metastable fragmentation of the cations using a new experimental
method. The large majority of the cations release mainly a neutral Ag3Br3 cluster. These decay channels are in full agreement with our recent ab initio DFT calculations, which show that Ag+-Ag+ repulsion is reduced due to a globally attractive interaction of their d orbitals. This effect leads to a particularly stable trimer (AgBr)3 and to quasi-planar cyclic structures of (AgBr)n clusters up to n = 6. We have shown that these two features may be extended to other silver halides, to silver hydroxides (AgOH)n, and to cuprous halide compounds.
Received 9 November 2000 and Received in final form 25 January 2001 相似文献
17.
C. Coudray G. Blaise M.J. Malliavin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(1):127-136
With the help of ab initio methods the clusters [(MgO)13Mg]
Q+
are simulated for Q = 0, 1, 2. Then, vacancy clusters [(MgO)12Mg2]
Q+
obtained by removing one oxygen atom are computed for Q running from 0 to 4. These clusters exhibit a slight sphericity and generally shorter interatomic distances than in the crystal.
The electronic densities variations are studied in function of Q. In particular, it is observed that the electronic density in the oxygen vacancy goes to a maximum when Q = 2. The ionisation potentials vary from approximately 4 to 14 eV when Q varies from 0 to 3, with a more rapid increase from Q = 1 to Q = 2. The stability study of vacancy clusters show that they experience a phase transition when their charge becomes equal
to 2, in accordance with the features mentioned above.
Received 14 September 1999 and Received in final form 2 December 1999 相似文献
18.
Systematic study of small BN clusters 总被引:2,自引:0,他引:2
S. Guerini P. Piquini 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):17-20
We performed a systematic investigation of the small BxNy (x + y? 6) clusters using the ab initio Hartree-Fock scheme plus second-order perturbation theory. The nature of the potential energy surface extrema are analyzed
through analytical total energy second derivatives. Ionization potentials, binding energies and the stability against some
possible reaction mechanisms are calculated. Based on these results we propose that the growing process for these clusters
is mainly due to the successive incorporation of BN molecules. A discussion of some mass spectrometry experimental results
is also presented.
Received 2 October 2000 相似文献
19.
C. Bobbert S. Schütte C. Steinbach U. Buck 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(2):183-192
The interaction of large ammonia and water clusters in the size range from <n> = 10 to 3 400 with electrons is investigated in a reflectron time-of-flight mass spectrometer. The clusters are generated
in adiabatic expansions through conical nozzles and are nearly fragmentation free detected by single photon ionization after
they have been doped by one sodium atom. For ammonia also the (1+1) resonance enhanced two photon ionization through the state with v = 6 operates similarly. In this way reliable size distributions of the neutral clusters are obtained which are analyzed in
terms of a modified scaling law of the Hagena type [Surf. Sci. 106, 101 (1981)]. In contrast, using electron impact ionization, the clusters are strongly fragmented when varying the electron
energy between 150 and 1 500 eV. The number of evaporated molecules depends on the cluster size and the energy dependence
follows that of the stopping power of the solid material. Therefore we attribute the operating mechanism to that which is
also responsible for the electronic sputtering of solid matter. The yields, however, are orders of magnitude larger for clusters
than for the solid. This result is a consequence of the finite dimensions of the clusters which cannot accommodate the released
energy.
Received 21 November 2001 相似文献
20.
K. Ohshimo H. Tsunoyama F. Misaizu K. Ohno 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):107-110
Intracluster electron transfer and oligomerization reaction were investigated by mass spectrometry of clusters of alkali metal
atom (M) with acrylonitrile (AN; CH2=CHCN). In the photoionization mass spectra of M(AN)n, magic numbers were clearly observed at n = 3k (k = 1-4 for M = Na and K, k = 1 for M = Li). The results of photodissociation of neutral K(AN)n indicate that the n = 3 cluster has an anomalous stability relative to other sizes of clusters. The C=C bond in vinyl molecules is also found
to be necessary to form the magic numbers by measuring the photoionization mass spectrum of K atom with propionitrile. These
results strongly support the intracluster anionic oligomerization reaction initiated by electron transfer from the alkali
atom. The quantum chemical calculations have revealed that the evaporation induced by excess energy generated by intracluster
oligomerization is important to form the magic numbers in the present clusters.
Received 29 November 2000 相似文献