共查询到20条相似文献,搜索用时 359 毫秒
1.
R. Popescu D. Macovei A. Devenyi R. Manaila P.B. Barna A. Kovacs J.L. Lábár 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(4):737-743
Structure of metal clusters and of the C60 matrix in Au/C60 and Cu/C60 nanosystems was investigated by X-ray diffraction. Results support a charge-transfer-type interaction at the metal-C60 interface, which affects the size distribution of metal clusters, favouring interstitial location of metal ions in the fullerite
lattice.
Received 5 February 1999 and Received in final form 7 July 1999 相似文献
2.
V.R. Galakhov M.A. Korotin N.A. Ovechkina E.Z. Kurmaev V.S. Gorshkov D.G. Kellerman S. Bartkowski M. Neumann 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(2):281-286
The electronic structure of LiMnO2 and Li2MnO3 was studied by means of X-ray photoelectron and soft X-ray emission spectroscopy. For LiMnO2, LSDA and LSDA+U calculations were carried out. The LSDA+U calculations are in rather good agreement with the measured valence-band structure as well as with the magnetic and electrical
properties of LiMnO2. It is shown that the band gap in LiMnO2 is determined by the charge-transfer effect.
Received 15 March 1999 and Received in final form 14 July 1999 相似文献
3.
T.A. Beu J. Onoe K. Takeuchi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(2):205-212
Non-orthogonal tight-binding molecular-dynamics is employed to calculate structural and vibrational properties of C36 and its oligomers (C36)
M = 2, 3, 4
. The lowest energy configuration of the C
36
cage is confirmed to have D
6h
symmetry. For the dimer, too, the D
2h
structure reported in the literature is found. The vibrational spectrum is identified with the power spectrum of the displacement
autocorrelation function. Additional vibrational properties are extracted from the dynamical matrix. For the monomer, fair
agreement with available ab initio calculations is achieved, with comparatively smaller deviations in the Raman-frequencies than for published semi-empirical
calculations. The features of the vibrational modes are correlated with the structural properties of the oligomers.
Received 24 November 2000 and Received in final form 24 August 2001 相似文献
4.
R. Koç H. Tütüncüler M. Koca 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(3):467-472
It is now well-known that electron (hole)-vibron coupling and hence Jahn-Teller (JT) effect is important understanding the
properties of C60 and related molecules. In this paper, we study H(2) coupling case to find the potential energy surfaces for the positively charged C60 molecule due to distortion. The H(2) Jahn-Teller system is of particular importance as this will be the JT effect displayed by C60 molecules removed with an electron. C60
+ is obtained by removing one electron from fivefold degenerate Hu highest occupied molecular orbital (HOMO) and a hole in HOMO interacts with the vibrational modes of C60 and symmetry is broken. We apply the method of symmetry breaking mechanism to obtain expressions for the potential energy
surface.
Received 27 December 1999 and Received in final form 15 May 2000 相似文献
5.
H. Deutsch K. Becker T.D. Märk 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):283-287
We report calculations of the electron-impact ionization cross-sections of selected dimers (homonuclear diatomic molecules)
and trimers (homonuclear triatomic molecules) using a method which relies only on macroscopic quantities in conjunction with
a “defect concept”. The empirically determined defect describes the deviation of the cluster (dimer, trimer) cross-sections
from a simple linear dependence on the cluster size. We compare the calculated cross-sections to experimental data for the
dimers S2 and F2 and the trimer O3 and we present predictions for the ionization cross-sections of Br2, I2, C2 and C3 for which no experimental data are available. Lastly, we extend the method to the calculation of ionization cross-sections
for the fullerenes C60 and C70.
Received 6 December 1999 and Received in final form 10 April 2000 相似文献
6.
G. Fischer E. Dormann 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(1):21-27
High-resolution 13C nuclear magnetic resonance with 1H cross polarization and 1H decoupling under magic angle spinning is measured for the quasi-one dimensional organic conductor diperylene hexafluorophosphate
(including tetrahydrofurane solvent molecules) at temperatures between 160 K and 270 K. Ab initio molecular orbital calculations are used for chemical shift analysis and for assignment of Knight shifted lines and individual
carbon positions. The coexistence of neutral perylene molecules and perylene radicals in the same radical cation salt is revealed.
From Knight and chemical shifts we were able to distinguish two inequivalent perylene radicals within the conducting stack.
The spin density distribution of the molecular electronic wave function is determined quantitatively for these radicals.
Received 29 June 1999 and Received in final form 4 November 1999 相似文献
7.
A. Lakhlifi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(2):211-222
Ammonia monomers have been adsorbed on argon clusters at low temperature K by Rohmund and Huisken [#!frfh97!#] using the pick-up technique. They measured the spectrum of the NH3 molecules in the region of the umbrella mode. Two broad bands centered around 970 and 1000 cm-1 with finer details were observed. The authors attempted to interpret the obtained spectrum on the basis of the free rotation
motions of the molecules. In this paper semi-empirical atom-atom potential energy calculations are performed for the ammonia
monomer adsorbed on a rigid face-centered-cubic (fcc)-type surface of the argon cluster. In the equilibrium position of the rigid molecule on the cluster surface the orientational
potential energy surface exhibits two quasi-equivalent minima separated by a potential barrier of about 100 cm-1. The symmetry of the molecular vibration-inversion double-well potential is destroyed; the inversion motion is then forbidden
in the ground state. On the basis of the two adsorption orientations, the vibrational frequency shifts are calculated and
the obtained infrared bar-spectrum agrees with the experimental one.
Received 6 April 1999 and Received in final form 19 July 1999 相似文献
8.
Ding Changgeng Yang Jinlong Cui Xiangyuan Wang Kelin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(1):123-126
Geometrical and electronic structures of C35X fullerenes with , N and Si as substitutional dopants have been studied. Three non-equivalent sites in the D6h structure of C36 have been considered for the substitution. We have found that the dopant has a strong tendency to substitute at sites where
the carbon atom contributes significantly to the frontier orbitals of C36 and has the weakest interaction with its nearest-neighbor atoms. The relative stability of C35Si and C35B (C35N) has been investigated and high chemical reactivity of C35Si has been predicted.
Received 8 July 1999 and Received in final form 4 October 1999 相似文献
9.
Shigehiro Komura T. Takeda Y. Kawabata S.K. Ghosh H. Seto M. Nagao 《The European physical journal. E, Soft matter》2001,5(3):329-336
Dynamical fluctuations of microemulsion and lamellar structures in a ternary amphiphilic system C12E 5/water/n-octane are studied by means of neutron spin echo spectrometry. The decay rate of the time correlation of the concentration
was analyzed in terms of a theory (M. Nonomura, T. Ohta, J. Chem. Phys. 110, 7516 (1999)), in which both van Hove and hydrodynamic interactions are considered. The result shows that the time correlation
function is expressed mostly by a single exponential determined exclusively by hydrodynamic interactions.
Received 1 December 1999 and Received in final form 12 March 2001 相似文献
10.
M. Ramm M. Ata T. Gross W. Unger 《Applied Physics A: Materials Science & Processing》2000,70(4):387-390
We report core-level and valence-band X-ray photoelectron spectroscopy (XPS) and carbon [
]K near-edge X-ray-absorptionfine structure spectroscopy (NEXAFS) results of plasma-polymerized C60. In comparison with evaporated C60 the C 1s peak is broader and asymmetric for the C60 polymer and its shake-up satellites diminished. Furthermore, the features of the valence-band as well as the features of
the π* antibonding orbitals of the C60 polymer are broader and reduced in intensity. Changes in the electronic structure are attributed to the polymerization of
C60, the post-plasma functionalization of the surface by oxygen after exposure to atmosphere, and the occurrence of amorphous
carbon.
Received: 28 May 1999 / Accepted: 31 August 1999 / Published online: 8 March 2000 相似文献
11.
V.I. Zubov N.P. Tretiakov I.V. Zubov 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):629-633
From simple topological considerations on the molecular shapes, a new method for calculating the coefficients of the Girifalco
intermolecular potential for various fullerenes is proposed. This eliminates the necessity for fitting the coefficients to
data of measurements for each specific fullerene. We calculate them for C76 and C84 and apply this potential to perform research on the equilibrium of these fullerites with their vapors. The temperature dependence
of the lattice parameters, the saturated vapor pressures and the enthalpies of sublimation is studied. Results are in good
agreement with available experimental data.
Received 13 January 2000 and Received in final form 18 June 2000 相似文献
12.
A. Qayyum M.N. Akhtar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):181-184
Light emission during sputtering of graphite targets with 1–10 keV Ne+, Kr+ and Xe+ beams has been investigated in the 180-600 nm wavelength range. Beside the characteristic lines of sputtered C1 and C1
+, a continuum superimposed with a number of broad structures was observed in the 250-520 nm range, and having a maximum at
386 nm. Mass analysis of the sputtered flux confirmed the presence of negative carbon clusters C
m
-
, C2
- being the dominant one. Ion beam parameters i.e. ion mass, energy, current density and ion dose were varied to identify the origin of the continuum emission. On the basis
of the experimental results, it is suggested that the continuum is predominantly due to the overlapping of various band systems
of sputtered C2 with a small contribution from the heavier sputtered carbon clusters Cm (m>2).
Received 24 September 1999 and Received in final form 11 February 2000 相似文献
13.
M.L. Gardel R. Vandenbosch B.P. Henry C. Cooper D.I. Will 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(1):79-81
The destruction cross-section for 22.5 and 50 keV C1- , for 10 and 50 keV C8
1- and for 50 and 75 keV C60
1- clusters in collisions with H2 has been measured by an attenuation method. The destruction of the cluster anions is dominated by electron detachment rather
than fragmentation and is of the order of the geometric cross-section. The cross-sections vary little with bombarding energy.
Received: 16 September 1998 / Received in final form: 23 February 1999 相似文献
14.
A.B.C. Patzer C. Chang E. Sedlmayr D. Sülzle 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,6(1):57-62
We present ab initio thermodynamic properties for seven different geometric isomers of molecular Al2O3 over a wide temperature range. The rigid rotator-harmonic oscillator approximation is used to calculate the partition function
as it is generally applied in thermodynamic studies of polyatomic molecules. The molecular data employed in setting up the
partition functions are taken from the theoretical results of ab initio MP2/6-31G(d) calculations. An analysis of the effects of the various contributions is made. The resulting thermodynamic functions
of Al2O3 are consistent with the JANAF thermochemical data compilation. Some thermochemical implications are discussed.
Received: 9 September 1998 / Received in final form: 2 October 1998 相似文献
15.
Z. Iqbal Y. Zhang H. Grebel S. Vijayalakshmi A. Lahamer G. Benedek M. Bernasconi J. Cariboni I. Spagnolatti R. Sharma F.J. Owens M.E. Kozlov K.V. Rao M. Muhammed 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(4):509-515
Evidence is presented for the formation of a solid phase based on the smallest fullerene, C20, in thin diamond-like carbon films deposited by ultraviolet laser ablation from diamond onto nickel substrates at room temperature
in the presence of 10-4 torr of cyclohexane or benzene. Laser desorption mass spectrometry from the films shows the presence of C20, C21 and C22 species, while micro-Raman spectroscopy and electron diffraction from selected particles together with first principle density-functional
calculations, indicate a cubic solid with dodecahedral C20 cages as building blocks. Unlike solid C60 and fully protonated C20, which are bound by van der Waals forces, the proposed structure is stabilized by linking of the C20 dodecahedra with bridging carbon atoms at interstitial tetrahedral sites to form a face-centered-cubic lattice with 22 carbon
atoms per unit cell.
Received 10 October 2002 / Received in final form 24 December 2002 Published online 6 March 2003
RID="a"
ID="a"e-mail: zafar.iqbal@njit.edu 相似文献
16.
A. Marucci P. Launois R. Moret A. Pénicaud 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):29-34
The phase diagram of the newly synthesized mixed crystal C60-biphenyl is investigated as a function of temperature by single-crystal X-ray scattering. Diffuse scattering investigations
evidencing complex disorder and local order effects are presented. Two phase transitions leading to two different doublings
of the high temperature unit cell are observed, at 212 K and 147 K. The first transition is attributed to the ordering of
twisted biphenyls, which couples to the orientational ordering of the C60 molecules as the temperature decreases. Full ordering of the C60 molecules is achieved below 100 K only, in the low temperature phase. The rich phase diagram of C60-biphenyl is due to the interplay between fullerene and biphenyl ordering phenomena.
Received 31 August 2001 and Received in final form 4 December 2001 相似文献
17.
K. Morgenstern E. Laegsgaard I. Stensgaard F. Besenbacher M. Böhringer W.-D. Schneider R. Berndt F. Mauri A. De Vita R. Car 《Applied Physics A: Materials Science & Processing》1999,69(5):559-569
We investigate atomic and molecular nanostructures on metal surfaces by variable low-temperature scanning tunnelling microscopy.
In combination with molecular dynamics calculations we achieve a detailed understanding of the stability of these structures.?Atomic
nanostructures in homoepitaxial metallic systems are thermodynamically only metastable. Two-dimensional islands on Ag(110)
decay above a threshold temperature of T
l=175 K. Caused by the anisotropy of the surface, distinct decay behaviours exist above and below a critical temperature of
T
c=220 K. Calculations based on effective medium potentials of the underlying rate limiting atomic processes allow us to identify
the one-dimensional decay below T
c as well as the two-dimensional decay above T
c.?In contrast to atoms, the intermolecular electrostatic interaction of polar molecules leads to thermodynamically stable
structures. On the reconstructed Au(111) surface, the pseudo-chiral 1-nitronaphthalin forms two-dimensional supermolecular
clusters consisting predominantly of ten molecules. Comparison of images with submolecular resolution to local density calculations
elucidates the thermodynamical stability as well as the internal structure of the decamers.
Received: 25 March 1999 / Accepted: 17 August 1999 / Published online: 6 October 1999 相似文献
18.
S. Kümmel T. Berkus P.-G. Reinhard M. Brack 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(2):239-245
The static electric dipole polarizability of Na
N
clusters with even N has been calculated in a collective, axially averaged and a three-dimensional, finite-field approach for , including the ionic structure of the clusters. The validity of a collective model for the static response of small systems
is demonstrated. Our density functional calculations verify the trends and fine structure seen in a recent experiment. A pseudopotential
that reproduces the experimental bulk bond length and atomic energy levels leads to a substantial increase in the calculated
polarizabilities, in better agreement with experiment. We relate remaining differences in the magnitude of the theoretical
and experimental polarizabilities to the finite temperature present in the experiments.
Received 8 November 1999 相似文献
19.
J. Sun G. Yu Y. Jiang S. Zhang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(1):83-88
The additivity rule is employed to obtain the total (elastic+inelastic) cross-sections for positron scattering from molecules
including a number of diatomic, polyatomic molecules (H2, N2, HCl, CO2, NH3, SF6, CH4, C2H4 and C3H8) over an incident energy range of 10-1000 eV. The total cross-sections (TCS) of the constituent atoms of molecules are obtained
by employing a complex optical model potential (composed of static, polarization and absorption potential). The present results
are compared with experimental data and other theoretical calculations, good agreement is obtained in intermediate- and high-energy
region.
Received: 11 November 1997 / Revised: 23 March 1998 / Accepted: 16 June 1998 相似文献
20.
D. Comparat C. Drag B. Laburthe Tolra A. Fioretti P. Pillet A. Crubellier O. Dulieu F. Masnou-Seeuws 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(1):59-71
We report on the formation of translationally cold Cs2 ground state molecules through photoassociation in the 1u attractive molecular state below the 6
s
1/2
+6
p
3/2
dissociation limit. The cold molecules are obtained after spontaneous decay of photoassociated molecules in a MOT and in
a dark SPOT. We also used polarized atoms, in the f
=3, m
f
=+3Zeeman ground state. Purely asymptotic and adiabatic calculations including hyperfine interaction and rotation are in excellent
agreement with observed structures. As expected, the 1u state is actually a pure long-range state, consisting of paired atoms, uniquely linked by the first terms of the multipole
expansion of the electrostatic interaction. A temperature of 20 K has been measured for the molecular cloud.
Received 19 July 1999 相似文献