共查询到20条相似文献,搜索用时 15 毫秒
1.
R. L. Zhou B. C. Pan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(3):367-372
We extensively search for the endohedral silicon-fullerene
structures of Si31–Si39 using the combination of a
tight-binding potential with the density functional theory. The
resulting structures of our best candidates characterize more
compact features comparing to previous isomers [J. Am. Chem. Soc. 126, 13845 (2004); J. Chem. Phys. 124, 164311 (2006)]. Most of our best candidates belong to new families
featuring different core/cage combinations or different original
carbon fullerene cages with respect to those of previous isomers.
Energy calculations reveal that our best candidates are more
stable than the previous best ones at the PW91 level, except for
n = 34 and 38. The predicted relative stabilities of these isomers remain even at finite
temperatures. In addition, the densities of dangling-bond atoms in
the surfaces of our Si33 and Si39 isomers are
significantly lower than the previous best candidates, as well as
lower than those of their neighbors. This finding together with
the densities of the active sites in the surfaces of the previous best candidates
of Si34 and Si38 is roughly consistent with the observed relative reactivities of the silicon
clusters in the size range of n = 31-39. 相似文献
2.
R. Resch A. Bugacov C. Baur B.E. Koel A. Madhukar A.A.G. Requicha P. Will 《Applied Physics A: Materials Science & Processing》1998,67(3):265-271
82 , M = Sc, Y, La) are discussed. The first 13C hyperfine structure has been analyzed in detail and at least seven electronically different groups of carbon atoms could
be assigned by simulations of the ESR spectra. The strong similarity of the 13C satellite structure suggests the preference of one cage isomer for the scandium group C82 endohedrals. The geometric structure and the electronic structure of all nine fullerene cage isomers of La@C82 were studied by approximate density-functional-based theoretical calculations. A C3v isomer was found as the most stable one. The manifold of 13C hyperfine coupling constants could be interpreted on the basis of the calculated spin density distributions.
Received: 15 September 1997/Accepted: 16 October 1997 相似文献
3.
K. Wu J. Li C. Lin C. Mang B. Zhuang 《Applied Physics A: Materials Science & Processing》2003,76(3):427-431
A theoretical model suitable for calculating infrared absorption-edges of molecular nonlinear optical (NLO) crystals is introduced
from high-level calculations of molecular vibrational spectra. The model is useful for elucidating the relationship between
the molecular vibration and macroscopic absorption edges on the IR side of organic nonlinear optical crystals. The first-principle
ab initio method carries out the calculations of IR absorption-edges of several typical molecular NLO crystals. These molecular NLO
crystals include urea, 2-methyl-4-nitroaniline (MNA), meta-dinotrobenzene (MDNB), 3-methyl-4-methooxy-4′-nitrostilbene (MMONS), and 3-hydroxyl-4′-nitrostilbene (HMONS). The calculated results are compared with the measurements and good agreement is found between them.
The experimentally unknown values of IR absorption-edges of some new synthesized crystals are predicted. The theoretical analyses
of the structural origins of IR absorption cut-offs are discussed. The results are helpful for the molecular simulation and
design of potential infrared molecular NLO crystals.
Received: 9 April 2002 / Accepted: 18 July 2002 / Published online: 28 October 2002
RID="*"
ID="*"Corresponding author. Fax: +86-591/3714946, E-mail: wkc@ms.fjirsm.ac.cn 相似文献
4.
G. Hermann B. Kaulakys G. Mahr 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(2):129-137
Results of broadening and shift measurements of Doppler-free two-photon lines for transitions from the ground state to the
Rydberg states with intermediate principle quantum numbers of atomic thallium perturbed by rare gases are reported. The rates
show a distinct behaviour in this range of principle quantum numbers and significant dependence on the total angular momentum
of the upper nP state. The experimental results are compared with calculations using a Van der Waals potential and a superposition of polarization
and Fermi potentials. Additionally, broadening and shift rates of the transition Tl 6P
3/2
-9P
3/2
have been measured for quadrupolar as well as for mainly scalar excitation. The rates for both kinds of excitation coincide
within the limits of error reflecting the small perturbation of the 6P
3/2
state compared to that of the upper 9P
3/2
state.
Received: 6 August 1997 / Revised in final form: 29 November 1997 / Accepted: 11 December 1997 相似文献
5.
Numerical calculations on the gradient and Laplacian forms of the position space Fisher information measure are reported using the 1-normalised Dirac-Fock densities (shape function), σ(r), for atoms H-Lr. It is shown that the difference in effective electrostatic potentials, corresponding to the gradient and the Laplacian form of Fishers' information, is completely defined by the shape function (the density per particle) at the nucleus, σ(r=0). The influence of relativistic effects on the Fisher information is recovered for the first time. 相似文献
6.
D. Beckmann S. Wanka J. Wosnitza J.A. Schlueter J.M. Williams P.G. Nixon R.W. Winter G.L. Gard J. Ren M.-H. Whangbo 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(3):295-300
The electronic structure of the quasi two-dimensional (2D) organic superconductor -(ET)2SF5CH2CF2SO3 was examined by measuring Shubnikov-de Haas (SdH) and angle-dependent magnetoresistance (AMRO) oscillations and by comparing
with electronic band-structure calculations. The SdH oscillation frequencies follow the angular dependence expected for a 2D Fermi surface (FS), and the observed fundamental frequency shows that the 2D FS is 5%
of the first Brillouin zone in size. The AMRO data indicate that the shape of the 2D FS is significantly non-circular. The
calculated electronic structure has a 2D FS in general agreement with experiment. From the temperature and angular dependence
of the SdH amplitude, the cyclotron and band effective masses were estimated to be and ,where g is the conduction electron g factor and the free electron mass. The band effective mass is estimated to be from the calculated electronic band structure.
Received: 3 March 1997 / Revised: 5 May 1997 / Received in final form: 5 November 1997 / Accepted: 10 November 1997 相似文献
7.
M. Bertolus V. Brenner P. Millié 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(2):197-205
A theoretical study of clusters with using density functional theory is presented. Tests of various functionals demonstrate that local spin density approximation
(LSDA) is the most adequate functional for the study of these systems. Structures, vibrational frequencies, and IR intensities
of the lowest energy isomer of the studied clusters obtained using LSDA are described, and the unusual properties of the Si-C
clusters are discussed. A quantitative analysis of the obtained structures was carried out, and relations between the coordinations,
interatomic distances, and angles observed in the Si-C clusters were obtained through introduction of the notion of coordination.
This analysis also shows that the carbon atoms mainly exhibit sp and sp2 hybridizations, and that a majority of silicon atoms do not hybridize. This study is the fi
rst step of the implementation of a semi-empirical potential, which would describe the moderately small Si-C clusters.
Received: 20 October 1997 / Received in final form: 16 December 1997 / Accepted: 17 December 1997 相似文献
8.
The question of whether the linear absorption spectra of metal clusters can be interpreted as density oscillations (collective
“plasmons”) or can only be understood as transitions between distinct molecular states is still a matter of debate for clusters
with only a few electrons. We calculate the photo-absorption spectra of Na2 and Na5
+ comparing two different methods: quantum fluid dynamics and time-dependent density functional theory. The changes in the
electronic structure associated with particular excitations are visualized in “snapshots” via transition densities. Our analysis
shows that even for the smallest clusters, the observed excitations can be interpreted as intuitively understandable density
oscillations. For Na5
+, the importance of self-interaction corrections to the adiabatic local density approximation is demonstrated.
Received: 1 July 2001 / Published online: 10 October 2001 相似文献
9.
A blue shifted photoluminescent emission in bis(2-(2′-hydroxyl phenyl)benzthiazolate)zinc (II) complex, ZBZT, arises out of the dimeric structure, typical of the localized electron density around the non-bridged ligand in the excited state of the complex. An average decay lifetime of 4.8 and 3.0 ns for the ligand and the complex, respectively indicates an energy transfer from the ligand to the metal. A PL quantum efficiency of about ?ZBZT=0.45 in DMF solution is observed, in comparison to the Alq3, complex, ?Alq3=0.116. Semi empirical ZINDO/S-SCF-CI calculations support the dominance of non-bridged ligand moiety in controlling the photoluminescent properties. An unusually broad white light (FWHM ∼220 nm) electroluminescent emission in the two layer device structure brings out the features of an exciplex formation between the active layer ZBZT/TPD interface, which is studied at different current densities. Such a broadened emission is verified for different thicknesses of the active layer substantiating the role of exciplex formation. 相似文献
10.
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
11.
* fluorescence radiation from the ion–ion recombination process in the gas volume during the preionization phase, therefore
allowing spatial resolution by partial imaging of the volume. Volume-integrated and temporally resolved measurements are carried
out to determine the average of absolute preionization densities by comparison with a theoretical model of the temporal behaviour
of the recombination process. Spatially resolved measurements reveal the distribution of the preionization density. The preionization
densities determined from spark and sliding/corona discharges schemes are considerably higher (ne
0?1012 cm-3) than those obtained from pulsed X-ray preionization (ne
0?107 cm-3).
Received: 3 October 1997/Revised version: 6 January 1998 相似文献
12.
C. Vadla 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(3):259-264
The total rate coefficient k for the energy pooling process has been measured in dependence on the ratio of the number densities of the Cs 6P fine-structure sublevels. The measurements
were performed applying the laser fluorescence method. From the set of the obtained data for k, the rate coefficients for the particular collisions were derived. The obtained values for the and collisions at T
= 600 K are , and , respectively. The value for k1 and the estimate for k3 are consistent with the data previously published by other authors. The rate coefficient k2 is reported for the first time.
Received: 10 June 1997 / Revised: 13 October 1997 / Accepted: 5 January 1998 相似文献
13.
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
14.
T. Wujec A. Jazgara J. Halenka J. Musielok 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):405-408
Stark broadening measurements and calculations of the Paschen γ spectral line of hydrogen ( λ = 1.094[:
MU
:]
m) are reported. Investigations have been performed at plasma electron densities between 1.4×10
15
cm
-3
and 3.7×10
15
cm
-3
. As the light source a wall-stabilized arc operated in a helium-hydrogen gas mixture at atmospheric pressure has been applied.
The radiation of the plasma emitted from nearly homogeneous plasma layers in end-on direction, was measured with the use of
a grating spectrometer equipped with a charge coupled device (CCD) detector. The radiance calibration was carried out against
light outputs originating from a tungsten strip radiation standard. The measured FWHM are compared with results of our calculations based on computer simulation techniques (full computer simulation method --
FCSM). Our broadening data are also compared with results of other theoretical approaches (MM-method, quasi-static approximation)
and with experimental data obtained at electron densities about one order of magnitude larger than ours.
Received 21 January 2003 Published online 24 April 2003
RID="a"
ID="a"e-mail: wujec@uni.opole.pl 相似文献
15.
Electron paramagnetic resonance experiments have shown that, depending on the doping procedure, two different S2− centers may coexist in KCl. These centers have the 2B2g and the 2B3g ground state, respectively. As no experimental ligand hyperfine data are available, it could not be determined whether the S2− molecular ion replaces a single halide ion (mono-vacancy site) or two nearest neighbor halide ions (di-vacancy site). Also, other defect models could a priory be considered. In this work, cluster in vacuo density functional theory calculations of the g and 33S hyperfine tensors show that the S2− ion at a mono-vacancy site has the 2B2g ground state, whereas S2− in a di-vacancy exhibits a 2B3g ground state. For the latter center, the possibility of charge compensation by a cation vacancy is also considered. The calculations indicate that a possible vacancy is not in the direct vicinity (nearest or next-nearest neighbor) of the S2− ion. 相似文献
16.
Y. Liu J. Dong D.Y. Xing 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(2):185-188
Minimizing total free energy by numerical calculations, we obtain the magnetic phase diagram of perovskite Mn oxides, such
as with , Ca, Sr, etc. in the whole doping region from x
=0 to x
=1 at temperature T
=0. It is discovered that a spiral state is stable in a low concentration of X ions while a canted state is stable in a high
concentration of X ions, and a ferromagnetic phase can exist in the intermediate concentrations when the antiferromagnetic
interaction is weak. The energy difference between spiral and canted states is found to be small when the Hund coupling is
large. Magnetic field induced spiral/canted phase transition is considered as a possible mechanism of the colossal magnetoresistance
(CMR) in the Mn oxides.
Received: 11 July 1996 / Revised: 7 December 1996 / Accepted: 24 July 1997 相似文献
17.
A. Banerjee M.K. Harbola 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(2):201-206
Employing a near exact Hylleraas wavefunction we calculate various third-order nonlinear optical properties for the helium
atom within the time-dependent Kohn-Sham theory. In our calculations we employ the adiabatic local-density approximation (ALDA)
for the exchange and correlation kernels fxc and gxc, and compare the numbers obtained by us with the available accurate theoretical as well as experimental results. Our results
demonstrate the accuracy of ALDA for the calculation of nonlinear optical properties of many electron systems.
Received: 22 June 1998 / Accepted: 15 October 1998 相似文献
18.
M. Saglam A. Türüt Ç. Nuhoglu H. Efeoglu T. Kılıçoglu M.A. Ebeoglu 《Applied Physics A: Materials Science & Processing》1997,65(1):33-37
2 /p-Si MOS structures were prepared in 0.1 M K2SO4 electrolyte with a pH of 7 (the 0.1 M KOH solution was buffered with H2SO4) at current densities of 3, 5, and 7 mA/cm2 and with four different pH values of the electrolyte at 3 mA/cm2. It is found that thermal annealing at a relatively low temperature can be used to improve the anodic MOS characteristics.
Moreover, of the pH and current density it followed that the pH has a dominant role in the interface electrical properties.
The lowest interface state densities at the maximum and the midgap positions are 7.1×1011 and 2.7×1010 eV-1cm-2 for a sample made with pH=7, J=3 mA/cm2. The characteristics of this sample seem satisfactory for device applications of anodized p-Si.
Received: 8 July 1996/Accepted: 22 January 1997 相似文献
19.
David J. Creasey Dwayne E. Heard Michael J. Pilling Benjamin J. Whitaker Martin Berzins Roger Fairlie 《Applied physics. B, Lasers and optics》1997,65(3):375-391
2 Σ+, v′=0) by air at 26±4 K. A value of 2.56±0.40×10-10 molecule-1 cm3 s-1 was obtained, a factor of more than four higher than at room temperature, and consistent with attractive forces dominating
the quenching of OH(A2Σ+). A d
etailed computational fluid dynamics (CFD) simulation of the supersonic free-jet expansion was performed, providing a two-dimensional
visualisation of temperature and density variations throughout the expansion. The CFD calculations reproduced the salient
features of the experimental temperature and density profiles along the centreline. Comparison between experiment and computation
has allowed validation of CFD codes.
Received: 31 January 1997/Revised version: 24 March 1997 相似文献
20.
Diana Bogdan 《Physics letters. A》2008,372(23):4257-4262
We investigate the geometry and electronic structure for complexes of α-cyclodextrin with butylparaben using DFT and Hartree-Fock calculations. The effect of solvent is explicitly taken into account. A Morokuma-Kiatura analysis of the bond energy is performed. We emphasize the role of the water, by pointing out the changes in the solvent's electronic structure for different docking geometries. 相似文献