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Vahedi Tafreshi H. Piseri P. Barborini E. Benedek G. Milani P. 《Journal of nanoparticle research》2002,4(6):511-524
We describe a simulation of the nanoparticle trajectories in a pulsed cluster beam source. Clusters, formed by condensation of atomic vapor in a helium bath, and considered here as rigid spheres having a diameter of 1.5nm, were tracked during their travel inside the source cavity, an aerodynamic lens, and a cylindrical nozzle. Steady state supersonic laminar flow of helium is considered in an axi-symmetric geometry aiming to simulate, within some limitations, the conditions under which cluster formation takes place in a pulsed microplasma cluster source. In spite of the unsteady nature of the pulsed source, the time scale characterizing particle motion in the flow field is significantly smaller than the characteristic time constant for the evolution of gas pressure in the source. For this reason, a steady simulation can shed some light on the understanding of processes governing nanoparticle motion in a pulsed vaporization source. The extent to which the Brownian diffusion can affect the particle extraction from the source is investigated. Simulations have shown that the Brownian motion perturbs the clusters from the trajectories dictated by the carrier gas and increases the rate of cluster deposition on the source internal walls. However, it does not hinder the aerodynamic focalization produced by the lens even in nano-size cluster regime. This result is qualitatively confirmed by experiment. 相似文献
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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
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Summary The lattice dynamics of Li-intercalated FePS3 has been studied by means of a force constant model generated by a set of short-range two-body potentials. The intercalated
phases have been investigated for the three stoichiometric compositions: Li0.5FePS3, LiFePS3, Li1.5FePS3, with the aim of analysing the evolution of the host lattice normal modes as a function of the concentration, and of finding
the dispersion of the new phonon branches induced by lithium. The above special values of lithium concentration have been
chosen because the size of the unit cell keeps the same as in the host material. The force constants are fitted to the infrared
data and the phonon dispersion curves and the phonon energy densities have been calculated. A spectroscopic method for monitoring
lithium migration in the host material is proposed. 相似文献
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First-principles calculations are presented for the layered perovskite Ca3Mn2O7. The results reveal a rich set of coupled structural, magnetic, and polar domains in which oxygen octahedron rotations induce ferroelectricity, magnetoelectricity, and weak ferromagnetism. The key point is that the rotation distortion is a combination of two nonpolar modes with different symmetries. We use the term "hybrid" improper ferroelectricity to describe this phenomenon and discuss how control over magnetism is achieved through these functional antiferrodistortive octahedron rotations. 相似文献
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Benedek Skublics 《Algebra Universalis》2011,66(1-2):63-67
Given a variety ${\mathcal{V}}$ with a constant 0 in its type and a lattice identity p ?? q, we say that p ?? q holds for congruences in ${\mathcal{V}}$ at 0 if the p-block of 0 is included in the q-block of 0 for all substitutions of congruences of ${\mathcal{V}}$ -algebras for the variables of p and q. Varieties that are congruence modular at 0 are characterized by a Mal??tsev condition. This result generalizes the classical characterization of congruence modularity by Day terms. 相似文献
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The surface Green function matching (SGFM) method is shown to be equivalent to the Green function method in its translationally and rotationally invariant formulation (IGF). Such equivalence between matching and invariance conditions makes the SGFM method easily applicable to the surface dynamics of ionic crystals, due to the existing possibility of deriving an effective short-range perturbation from the invariance conditions. An application to the inelastic scattering of He from LiF(001) in the eikonal approximation is presented. 相似文献
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