共查询到20条相似文献,搜索用时 62 毫秒
1.
V. F. Elesin N. N. Degtyarenko N. V. Matveev A. I. Podlivaev L. A. Openov 《Journal of Experimental and Theoretical Physics》2005,101(1):44-55
The existence of a metastable cluster He 4 * with total spin S = 2 is predicted. The cluster consists of two covalently bound excited spin-polarized triplet He 2 * molecules and is rectangular in shape. The electron wavefunctions, the dependence of the energy He 4 * system on the distance between the He 2 * triplet molecules, the atomic spacing, the frequency spectrum of natural oscillations of the cluster, and other characteristics are calculated from first principles. It is shown that the metastable state is formed if one of the excited He 2 * molecules is in the 3Σ u + state, while the other is in the 3Πg state. The radiation lifetime τ of the metastable cluster He 4 * is calculated; it is found to range from 100 to 200 s, which is much longer than the lifetime τ ≈ 20 s of the triplet molecule He 2 * (3Σ u + ). The height U ≈ 0.5 eV of the potential barrier preventing the departure from the local energy minimum is determined. The energy Eacc ≈ 9 eV/atom accumulated in the He 4 * cluster is calculated; this energy considerably exceeds the energy of known chemical energy carriers. It is shown that the accumulated energy is released virtually completely during decomposition of the He 4 * cluster into individual helium atoms. This means that helium clusters are a promising material with a high accumulated energy density (HEDM). 相似文献
2.
The method is described and the experimental results are presented on the temperature determination of the (CF3I)
N
clusters in a beam (N ⩽ 102 is a number of monomers in a cluster) using SF6 molecules from intersecting molecular beam as probe thermometers. The SF6 molecules are captured by clusters in the crossed cluster and molecular beams and, after a certain time, sublimate from the
surface of clusters carrying information on the velocity and temperature (internal energy) of clusters. Using time-of-flight
(TOF) method the kinetic energy (velocity) of sublimated SF6 molecules was measured and the temperature of clusters was determined to be T
cl = (88 ± 15) K. 相似文献
3.
In this paper we report our calculations on several important total cross-sections (TCSs) of positron impact on isoelectronic
N2 and CO molecules, treated in the complex spherical potential formalism. Basically the total (complete) cross-section Q
T consists of elastic and inelastic contributions. Our total inelastic cross-section (Q
inel) contains ionization and electronic excitations together with positronium formation. Our goal here is to bifurcate Q
inel further to deduce total ionization cross-section, using the ‘complex scattering potential–ionization contribution’ (CSP-ic)
method of electron–atom/molecule scattering. The present range of positron energy is 15–2000 eV. All the resulting cross-sections
are in a good general accord with the existing data. This work highlights the importance of various scattering channels in
e + -N2 and e + -CO interactions at intermediate and high energies. 相似文献
4.
A. Ya. Kupryazhkin M. A. Kovalenko A. V. Koromyslov A. N. Zhiganov 《Physics of the Solid State》2011,53(6):1198-1201
The concentration of unbound neutral anion vacancies in cerium gadolinium ceramics Ce0.8Gd0.2O1.9 with a submicrocrystalline structure has been determined using low-temperature helium defectoscopy at temperatures ranging
from 613 to 773 K and at saturation pressures from 0.05 to 12 MPa. It has been found that the energy of dissociation of impurity-vacancy
complexes is 1.1 ± 0.2 eV, and the energy of dissolution of helium in defects is −0.8 ± 0.2 eV. The obtained results have
been compared both with the experimental data on the energy of interaction between helium and ions of the cerium gadolinium
ceramics and with the results of the quantum-chemical calculations. It has been demonstrated that the anomalously low value
of the energy of helium dissolution in the studied ceramic samples is determined by the chemical interaction of helium with
the nearest environment of the cerium cations. 相似文献
5.
It has been found that SF6 molecules captured by large van der Waals clusters (CO2) N (where N ≥ 102 is the number of monomers in a cluster) in intersecting molecular and cluster beams sublimate from the surface of clusters after a certain time and carry information on the velocity and temperature (internal energy) of clusters. Experiments have been carried out for detecting these molecules by means of a pyroelectric detector and the infrared multiphoton excitation method. The multiphoton absorption spectra of molecules sublimating from the surface of clusters have been obtained. The temperature of the (CO2) N nanoparticles in the cluster beam has been estimated using these spectra and comparing them with the infrared multiphoton absorption spectra of SF6 in the initial molecular beam. 相似文献
6.
Silvete C. Guerini David L. Azevedo Maria C. A. Lima Ivana Zanella Josué Mendes Filho 《Central European Journal of Physics》2008,6(1):105-108
This paper deals with quantum mechanical interaction of no
3− with (5,5) and (8,0) swcnts. To perform this we have made an ab initio calculation based on the density functional theory. In these framework the electronic density plays a central role and it
was obtained of a self-consistent field form. It was observed through binding energy that NO3− molecule interacts with each nanotube in a physisorption regime. We propose these swcnts as a potential filter device due to reasonable interaction with NO3− molecule. Besides this type of filter could be reusable, therefore after the filtering, the swcnts could be separated from NO3− molecule.
相似文献
7.
Equilibrium geometries, charge distributions, stabilities and electronic properties of the Ag-adsorbed (MgO)
n
(n = 1–8) clusters have been investigated by density functional theory (DFT) with generalized gradient approximation (GGA) for
exchange-correlation functional. The results show that hollow site is energetically preferred for n⩾4, and the incoming Ag atoms tend to cluster on the existing Ag cluster. The Mulliken populations indicate that the interaction
between the Ag atom and Magnesia clusters is mainly induced by a weak atomic polarization. The adsorbed Ag atom only causes
charge redistributions of the atoms near itself. The effect of the adsorbed Ag atom on the bonding natures and structural
features of Magnesia clusters is minor. Furthermore, the investigations on the first energy difference, fragmentation energies
and electron affinities show that the Ag(MgO)4 and Ag(MgO)6 are the most stable among studied clusters.
Supported by the Startup Fund of High-level Personal for Shihezi University (Grant No. RCZX200747) 相似文献
8.
E. Scifoni F.A. Gianturco 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(3):323-333
Experimental and theoretical studies in large ionic helium clusters have suggested the presence of a diatomic (and occasionally triatomic) charged molecular core surrounded by the other atoms which are bound to it by weaker interactions [1-3]. The understanding of the interactions between the system He 2 + and an additional He atom of the cluster is therefore important in order to start modelling the full cluster interaction potential. In the present work we carry out a new set of calculations on the full potential and on the bound states supported by the He 2 + isolated ion and further extend them to generate a Rigid Rotor (RR) potential energy surface (PES) for the triatomic system with He 2 + kept at its equilibrium geometry (2.0 a.u.). The 13 bound states which were found and the overall angular anisotropy that exists for this Potential Energy Surface (PES) are discussed in detail. We additionally show results of calculations on the surface vibrational extension to nine different values of the He 2 + interatomic distance, thereby generating a fuller, three-dimensional interaction potential. A simpler modelling of the latter via “Pseudo Rigid Rotor” calculations for the bound states with a vibrationally excited core is also presented and discussed. 相似文献
9.
A.R.W. Mc Kellar 《Applied physics. B, Lasers and optics》2008,90(2):213-225
Helium clusters, HeN-X, containing a probe molecule, X, are studied by infrared spectroscopy for the size range N≈1∼100. Spectra are observed
using a supersonic jet expansion and a tunable diode laser source operating in a rapid-scan (sweep integration) mode. The
pulsed jet uses a dilute gas mixture of the probe molecule in helium, with relatively high backing pressures (5–50 bar), and
a cooled (80–295 K) nozzle. Sensitivity is enhanced by multi-passing the laser beam through the jet with a toroidal mirror
system. The clusters are larger than van der Waals dimers and trimers, but smaller than those encountered in the field of
helium nanodroplets (N≈103–105). Furthermore, individual cluster sizes are resolved here, but not with nanodroplets, and infrared absorption is detected
directly (change in transmitted laser intensity), rather than indirectly (change in cluster fragmentation). Trends in the
spectra are described for five probe molecules, X=CO, SiH4, OCS, N2O, and CO2. Superfluid effects dominate for clusters larger than N≈8. Notable results include the unexpected observation of broad oscillations
in the effective rotational constants as a function of cluster size.
PACS 33.20.Ea; 34.30.+h; 36.40.Mr; 42.55.Px 相似文献
10.
Low-lying equilibrium geometric structures of Phosphorus-doped aluminum cluster Al
n
P (n = 2–12) clusters obtained by an all-electron linear combination of atomic orbital approach, within spin-polarized density
functional theory, are reported. The binding energy, dissociation energy, and stability of these clusters are studied within
the local spin density approximation (LSDA) and the three-parameter hybrid generalized gradient approximation (GGA) due to
Becke-Lee-Yang-Parr (B3LYP). Ionization potentials, electron affinities, hardness, and static polarizabilities are calculated
for the ground-state structures within the GGA. It is observed that symmetric structures with the P atom occupying a peripheral
position are lowest-energy geometries of Al
n
P (n = 2, 4–11), while the P impurities of Al3P and Al12P prefer to occupy internal sites in the aluminum clusters. Generalized gradient approximation extends bond lengths as compared
to the LSDA lengths. The odd-even oscillations in the dissociation energy, the second differences in energy, the HOMO–LUMO
gaps, the ionization potential, the electron affinity, and the hardness are more pronounced within both GGA and LSDA. The
stability analysis based on the energies clearly shows the clusters with an even number of valence electrons are more stable
than clusters with odd number of valence electrons. 相似文献
11.
N. Kaiser 《The European Physical Journal A - Hadrons and Nuclei》2007,31(2):207-212
We calculate at two-loop order in chiral perturbation theory the electromagnetic corrections to the leading-order 2π exchange
NN interaction proportional to g
A
0 and g
A
2. The resulting 2πγ exchange potential contains isospin-breaking components which reach up to about -2% of the corresponding
isovector 2π exchange potential. With a value of only -17keV at r = m
π
-1 = 1.4fm the charge-independence breaking central potential obtained here is negligibly small in comparison to the one generated
by the isoscalar c3 contact vertex. Our calculation confirms that the largest long-range isospin-violating NN potentials arise from the 2πγ exchange diagrams involving the large low-energy constants c
4 ≃ - c
3 ≃ 3.3GeV^-1 representing the important Δ(1232) dynamics. 相似文献
12.
Effect of the molecular structure on the gas-surface scattering
studied by supersonic molecular beam
T. Kondo H. S. Kato T. Yamada S. Yamamoto M. Kawai 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(1):129-138
The experimental apparatus for investigating the gas-surface interaction has
been newly developed. The coherent length of the helium, the energy
resolution and the angular spread of the beam in the apparatus were
established as ω= 16 nm,
DE/E = 2.4%\Delta E/E = 2.4{\%}
and Δθ= 0.5○, respectively, through the
measurements of the time-of-flight of He beam and of the angular intensity
distributions of He scattered from LiF(001). The angular intensity
distributions of Ar, N2 and CO scattered from the LiF(001) surface
along the [100] azimuthal direction were then measured as a function of
incident translational energy. The effects of the molecular structural
anisotropy and center-of-mass position on the gas-surface inelastic
collision at the corrugated surface are discussed with predictions based on
a recently developed simple classical theory of the ellipsoid-washboard
model. 相似文献
13.
I. Popov T. Kunze S. Gemming G. Seifert 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):439-446
The preferred adsorption sites and the propensity for a self-organised growth of the molybdenum sulfide cluster Mo6S8 on the Au(111) surface are investigated by density-functional band-structure calculations with pseudopotentials and a plane
wave basis set. The quasi-cubic cluster preferentially adsorbs via a face and remains structurally intact.
It experiences a strong, mostly non-ionic attraction to the surface
at several quasi-isoenergetic adsorption positions. A scan of the potential energy surface exhibits only small barriers between
adjacent strong adsorption sites. Hence, the cluster may move in a potential well with degenerate local energy minima at room
temperature. The analysis of the electronic structure reveals a negligible
electron transfer and S-Au hybridised states, which indicate that the cluster-surface
interaction is dominated by S-Au bonds, with minor contributions from
the Mo atom in the surface vicinity. All results indicate that Mo6S8 clusters
on the Au(111) surface can undergo a template-mediated self-assembly to an ordered inorganic monolayer, which is still redox
active and may be employed as surface-active agent in the integration of noble metal and ionic or biological components within
nano-devices.
Therefore, a classical potential model was developed on the basis of the DFT data,
which allows to study larger cluster assemblies on the Au(111). 相似文献
14.
I. V. Davydov 《Physics of the Solid State》2007,49(6):1201-1206
The effect of heating of the electronic subsystem on the thermal stability of C60 and C20 fullerenes and a (C20)2 cluster molecule is investigated theoretically. It is demonstrated that the excitation of electrons to upper energy levels in accordance with the Fermi-Dirac distribution function does not lead to a substantial change in the activation energy E a for decay of the C20 fullerene. The stability of the C60 fullerene and the (C20)2 cluster molecule likewise does not change radically. However, the inclusion of corrections associated with the finite sizes of the heat bath leads to the activation energy E a which is in better agreement with the calculated height of the potential barrier preventing the cluster decay. 相似文献
15.
We report the results of calculations which were performed to investigate equilibrium structures, electronic and magnetic
properties of stoichiometric (NiSn)
n
clusters with n = 1–6 within the framework of density functional theory. The calculated results show that the structural arrangement of (NiSn)
n
clusters is dominated by the Ni-Sn and Ni-Ni interactions. We find that these binary clusters show significant variation
in the geometries as compared to that of the host nickel clusters. The preference for tetrahedron unit of Ni3Sn is seen in the lowest-energy configuration of these clusters. The multi-centre bonding between Ni atoms play an important
role in stabilizing the stoichiometric Ni-Sn clusters. Doping of Sn atoms enhances the binding energy and reduces the ionization
potential of nickel clusters. These binary clusters prefer the lowest spin state. For (NiSn)6 the magnetic moment is 0 μB. The complete quenching of the cluster magnetic moment appears to be due to the antiferromagnetic alignment of atomic spins
as revealed by the spin density plots. 相似文献
16.
S. V. Trukhanov A. V. Trukhanov A. N. Vasiliev H. Szymczak 《Journal of Experimental and Theoretical Physics》2010,111(2):209-214
The magnetic and thermal properties of the anion-deficient La0.70Sr0.30MnO2.85 manganite are investigated in wide temperature (4–350 K) range, including under hydrostatic pressure (0–1.1 GPa). Throughout
the pressure range investigated, the sample is spin glass with diffused phase transition into paramagnetic state. It is established,
that spin glass state is a consequence of exchange interaction frustration of the ferromagnetic clusters embeded into antiferromagnetic
clusters. The magnetic moment freezing temperature T
f
of ferromagnetic clusters increases under pressure, freezing temperature dependence on pressure is characterized by derivative
value ∼4.5 K/GPa, while the magnetic ordering T
MO temperature dependence is characterized by derivative value ∼13 K/GPa. The volume fraction of sample having ferromagnetic
state is V
fer ∼ 13% and it increases under a pressure of 1.1 GPa by ΔV
fer ≈ 6%. Intensification of ferromagnetic properties of the anion-deficient La0.70Sr0.30MnO2.85 manganite under hydrostatic pressure is a consequence of oxygen vacancies redistribution and unit cell parameters decrease.
The most likely mechanism of frustrated exchange interactions formation is discussed. 相似文献
17.
N. E. Sluchanko D. N. Sluchanko V. V. Glushkov S. V. Demishev N. A. Samarin N. Yu. Shitsevalova 《JETP Letters》2008,86(9):604-607
Within a wide temperature range of 1.8–300 K, the Hall effect in holmium dodecaboride is investigated. The measurements of
the angular dependences of the Hall resistance ρH(φ, T, H) for HoB12 performed in a high magnetic field up to 80 kOe at helium and intermediate temperatures made it possible to separate the
normal and anomalous contributions to the Hall effect. Analysis of the anomalous component behavior in the paramagnetic and
Néel phases suggests the appearance of the 5d-state magnetic polarization (the spin polaron effect) and makes it possible to compare the revealed features of the Hall
coefficient R
H(T, H) with the H-T magnetic phase diagram of HoB12. 相似文献
18.
We determined and tried to understand the spectroscopic and structural properties of small LiAr and LiAr2 molecules within a simple model considering LiAr as a result of interaction between a valence electron and a LiAr+ molecular ion. Potential energy curves, spectroscopic constants, and vibrational levels corresponding to the Li(2s, 2p, 3s, and 3p)+Ar dissociation are reported for the LiAr molecule. The depth of the potential well for the X
2Σ+ ground state is found to be 50 cm−1 (the corresponding experimental value is (42.5±1.2) cm−1 [1]). R
e is determined to be 9.36 a.u. (the experimental value is 9.24 a.u.). For the first excited state A, R
e = 4.97 a.u. and D
e = 993cm −1 (the corresponding experimental values are 4.68 a.u. and (925−40) cm−1, respectively [1]). The spacing between the vibrational levels for the ground and first excited states is in very good agreement
with the experiment. For the ground state, the difference between our results and the data of the most recent experiment is
about 1 cm−1. The model has been extended to study the LiAr2 molecule in two forms (linear and triangular). We have determined the potential energy surfaces of the states dissociating
to Li(2s, 2p)+Ar2 and thus found the triangular form to be more stable as compared to the linear one. We have also calculated the transition
energy between the ground state and first excited states of this molecule. The emission spectrum of the Li(2s)+Ar2→Li(2p)+Ar2 transition in both forms redshifts as compared to the Li(2s)→Li(2p) atomic transition. 相似文献
19.
Q. Sun Q. Wang X.G. Gong V. Kumar Y. Kawazoe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):77-81
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
20.
P. Jasik J. Wilczyński J. E. Sienkiewicz 《The European physical journal. Special topics》2007,144(1):85-91
We report adiabatic potential energy curves of the
Li2
+ molecule. Our curves are tabulated according to
internuclear distance from 2 a0 to 100 a0. We
compare our theoretical results with the ones calculated by other
authors and potential energy curves derived from experiments. For
the ground state and 17 excited states we calculate spectroscopic
parameters and compare them with parameters obtained by other
authors. For the first time we present three new minima for
32Σu
+, 42Σu
+ and 22Πg
excited states. In our approach we use the configuration interaction
method where only the valence electrons of Li atoms are treated
explicitly. The core electrons are represented by pseudopotential.
All calculations are performed by means of MOLPRO program package. 相似文献