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11.
Tamotsu Kohyama 《Journal of statistical physics》1991,63(3-4):637-651
A class of simple two-dimensional cellular automata with particle conservation is proposed for easy simulations of interacting particle systems. The automata are defined by the exchange of states of neighboring cells, depending on the configurations around the cells. By attributing an energy to a configuration of cells, we can select significant rules from the huge number of possible rules and classify them into several groups, based on the analogy with a binary alloy. By numerical calculations, cluster growth is found in two kinds of phases which reveal gas-solid coexistence and liquid droplets. Normalized scaling functions are obtained, and dynamical scaling is examined. 相似文献
12.
Shoaib Ahmad 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):309-318
The mechanisms and processes of the formation of the regenerative soot in a graphite hollow cathode discharge that produces
and emits carbon clusters are presented. Mass spectrometry with a specially designed E×B velocity filter analyzes the entire range of the charged clusters from C
1 to ∼C
4300. The state of the carbon vapour within the source is evaluated by using the characteristic line emissions from the carbonaceous
discharge whose formative mechanisms depend upon the kinetic and potential sputtering of the sooted cathode. The carbonaceous
discharge generates atomic and ionic C and its clusters C
m (m≥ 2), noble gas metastable atoms and ions, energetic electrons and photons in the cavity of the graphite hollow cathode. The
parameters of soot formation and its recycling depend critically on the discharge parameters, the geometry of the hollow cathode
and 3D profile of the cusp magnetic field contours.
Received 2nd July 2001 and Received in final form 10 September 2001 相似文献
13.
Michael Grätzel 《Journal of Sol-Gel Science and Technology》1994,2(1-3):673-677
Transparent nanocrystalline films of oxide semiconductors such as TiO2 and Fe2O3 have been prepared on a conducting glass support employing a sol-gel procedure. The films are composed of nanometer-sized particles sintered together to allow for percolative charge carrier transport. The internal surface of these films is very high, roughness factors of the order of 1000 being readily obtained. Electric polarization was applied for forward and reverse biasing of the films and the resulting optical changes have been analyzed to derive their flat band potential. Band gap excitation of such nanocrystalline semiconductors produces electron-hole pairs which migrate through the film to be collected as electric current. Steady state photolysis and time resolved laser techniques have been applied to scrutinize the mechanism of light induced charge separation within the nanostructure. When derivatized with a suitable chromophore, TiO2 films give extraordinary efficiencies for the conversion of incident photons into electric current, exceeding 90% for certain transition metal complexes within the wavelength range of their absorption band. The underlying physical principles of these astonishing findings will be discussed. Exploiting this discovery, we have developed a new type of photovoltaic device whose overall light to electric energy conversion yield is 10% under simulated AM 1.5 solar radiation. 相似文献
14.
F.F. Karpeshin J. da Providência C. Providência J. da Providência Jr 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):319-326
Two types of extreme collective motion, large-amplitude many-phonon vibration of the ionic core and rotation of the cluster
with high angular momenta, are considered. The interplay between vibration and collective motion towards fission is discussed.
A new mechanism of formation and rupture of the neck is proposed which is based on the Franck-Condon principle, and accounts
for the interplay between vibration and fission. Under rotation, the change of the shape of the cluster and a phase transition
from axially symmetric to triaxial ellipsoid are predicted. For studying the effects, vibrational motion can be induced by
laser radiation. Rotational motion may arise in collisions of clusters.
Received 26 April 2001 and Received in final form 15 October 2001 相似文献
15.
Granular films prepared from well-defined In clusters embedded in Kr (? 10-40 at % Kr) show sharp resistance anomalies very close to the superconducting transition temperature. The observed resistance peak(s), which go(es) above the normal state resistance RN and which can be as high as ? 1.5 RN, can be explained by a “mesoscopic” effect: Superconducting percolation aggregates of size ξρ, larger than the superconducting coherence length ξS, but smaller than the quasiparticle relaxation length λQ*, have a superconducting gap, but are not yet able to carry a supercurrent. 相似文献
16.
Sulfide cluster-derived ensembles are promising models of the active sites in commercial hydrotreatment catalysts. A series of sulfide clusters were adsorbed intact onto high-surface-area γ-alumina, magnesium oxide and activated carbon supports, then pretreated to produce highly dispersed catalytic ensembles with sizes similar to those of their precursor clusters. The activities of the bimetallic cluster-derived catalysts were significantly higher than those of the monometallic catalysts. We took this as evidence that direct interactions between molybdenum and the promoter element cause the promotional effect observed in commercial hydrotreatment catalysts. The hydrodesulfurization and hydrodenitrogenation activities correlated with the extent of molybdenum reduction. Our results suggested that the active sites in promoted hydrotreatment catalysts are centered on molecular-scale ensembles containing molybdenum, sulfur and the promoter element. 相似文献
17.
Spin-flip (paramagnetic) scattering and neutron depolarization studies were performed on Ce2Fe17 in its paramagnetic phase on the Dhruva neutron polarization analysis spectrometer. The absence of normalQ dependence of the scattered spin flip intensity shows that Ce2Fe17 is not a normal paramagnetic and there exist superparamagnetic clusters of sufficiently large dimensions (~100Å). The observed neutron depolarization gives an indication of the dynamics of these Ce2Fe17 superparamagnetic clusters. 相似文献
18.
S. F. Chekmarev R. Mitri V. Bonaci-Koutecký 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):45-48
The ab initio molecular
dynamics (AIMD) [1] is combined with the heuristic, successive
confinement method of surveying a potential energy surface (PES)
[2], thereby offering a framework for the simulation study of
kinetics and equilibrium properties of metallic clusters. This
approach is applied to the study of Au4,
a cluster possessing a simple but specific PES, which consists
of very shallow and deep basins and due to this presents a
challenge to the conventional AIMD methods. Among other things,
the probabilities of the transitions between isomers have been
found, and on this basis, both the time-dependent and
equilibrium populations of the isomers have been calculated for
the conditions typical of the NeNePo experiments [3] in the
femtosecond pump-probe spectroscopy. 相似文献
19.
The Lombardo–Imbihl–Fink (LFI) ODE model of the NO+NH3 reaction on a Pt(1 0 0) surface shows stable relaxation oscillations with very sharp transitions for temperatures T between 404 and 433 K. Here we study numerically the effect of linear diffusive coupling of these oscillators in one spatial dimension. Depending on the parameters and initial conditions we find a rich variety of spatio-temporal patterns which we group into four main regimes: bulk oscillations (BOs), standing waves (SW), phase clusters (PC), and phase waves (PW). Two key ingredients for SW and PC are identified, namely the relaxation type of the ODE oscillations and a nonlocal (and nonglobal) coupling due to relatively fast diffusion of the kinetically slaved variables NH3 and H. In particular, the latter replaces the global coupling through the gas phase used to obtain SW and PC in models of related surface reactions. The PW exist only under the assumption of (relatively) slow diffusion of NH3 and H. 相似文献
20.