Vibration Properties of Thin Films of Transition 3d-Metals on the Cu (111) Surface

Russian Physics Journal - Using the potentials, generated by a tight binding approximation, the equilibrium atomic structure and the phonon spectra of Cr and Ni thin films (one monolayer) deposited...     

Vibrational states of a cobalt dimer on the (111) and (001) copper surfaces

The results of calculations of the total (lateral and vertical) relaxation of the (001) and (111) copper surfaces in the presence of a small cluster of cobalt adatoms, local vibrational density of states and polarizations of these states are presented. The calculations were performed using the atomic interaction potentials in a tight binding approximation. An analysis of the results obtained showed that the presence of a cobalt dimer gives rise to modification of the vibrational states of the copper surface and generation of new modes localized both on the adatoms of the cluster and the surface atoms of the substrate. The revealed anisotropy of surface relaxation along [001] results in deformation of atomic bonding and splitting of the vibrational modes of the dimer. The lifetimes of the vibrational states of the dimer are found to be nearly equal for both surfaces under study, with a frequency shift being however observed. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp.73–78, December, 2008.     

Vibrational modes on the Al\,(111) - (\sqrt 3 \times \sqrt 3 )R30^\circ - Na surface

The vibrational spectra on the $Al\,(111) - (\sqrt 3 \times \sqrt 3 )R30^\circ - Na$ surface are calculated by the embedded atom method. Surface relaxation, dispersion of surface phonons, local density of surface states, and polarization of vibrational modes of adatoms and substrate atoms are discussed in the present paper. The theoretical results obtained agree well with the available experimental data and can be used for their interpretation.     

Diffusion properties of Cu(0 0 1)-c(2 × 2)-Pd surface alloys

Structural and diffusion properties of a Cu(0 0 1)-c(2 × 2)-Pd surface and sub-surface ordered alloys are studied by using interaction potentials obtained from the embedded-atom method. The calculated diffusion energies are in agreement with observed kinetics of the surface alloy formation and confirm stability of the underlayer alloy. Activation energy of planar diffusion of palladium at the initial stage of the alloy formation as well as the activation energy of the overlayer-underlayer diffusion of the Pd atoms are in good agreement with those obtained by the scanning tunneling microscopy and low energy electron diffraction measurements, respectively.     

Vibrational states of the Cu(100) surfaces with nickel adlayers

The vibrational spectra of the Cu(100) surface covered with one or two Ni monolayers are calculated using the embedded-atom method. The surface relaxation, the dispersion of surface phonons, and the polarization of vibrational modes of the adsorbate and the substrate are discussed in detail. The theoretical results are in good agreement with experimental data and can be used for their interpretation. The changes observed in the interatomic interactions upon application of nickel adsorbates to the copper substrate are considered.     

Comparative study of vibrations in submonolayer structures of potassium on Pt(111)

We present results of a comparative study of the vibrational spectrum and local density of phonon states in ordered p(2 x 2) and (√3 x √3)R30° structures formed by potassium atoms on the Pt(111) surface. The calculations were performed with tight-binding interatomic interaction potentials. It was found that the mode associated with vertical displacements of K adatoms has an energy of about 20 meV in both K structures. The strength and energy of this mode slightly decreases with increasing coverage. This result is in good agreement with available experimental data. As in time-resolved second harmonic generation measurements, we observed low frequency modes for both structures considered, which are caused by the interaction of potassium with the second layer of the substrate.     

Liquid phase hydrogenolysis of dibenzyl ether over metals of the VIIIth group

It has been shown that depending on the catalyst and the solvent used, during the conversion of dibenzyl ether to toluene hydrogenolysis of C-O ether bonds, dehydrogenation and hydrogenolysis of benzyl alcohol formed, hydrogenation and decarbonylation of benzaldehyde, and the recombination of benzyl radicals and the benzylation of toluene can take place. The activity of catalysts in hydrogenolysis reactions of dibenzyl ether and benzyl alcohol to produce toluene decreases as follows: Pd/C>Pd>Raney Ni>Rh, whereas the selectivity drops down in the order: Raney Ni>Pd>Pd/C>Rh. The reaction rates depend on the solvent and diminish in the order: ethanol>2-propanol>benzene.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1257–1261, July, 1993.     

Synthesis,Structure, and Haptotropic Interconversions of Tungsten Cycloheptatrienyl–Acetonitrile–Carbonyl Complexes

Russian Journal of Coordination Chemistry - Tungsten cycloheptatrienyl complexes (η7-C7H7)W(CO)2I (I), [(η3-C7H7)W(CO)2(CH3CN)3]PF6 (II), and [(η7-C7H7)W(CO)2(CH3CN)]PF6 (III) (CIF...     

Theory of spoof plasmons in real metals

In this Letter we develop a theory of spoof plasmons propagating on real metals perforated with planar periodic grooves. Deviation from the spoof plasmons on perfect conductor due to finite skin depth has been analytically described. This allowed us to investigate important propagation characteristics of spoof plasmons such as quality factor and propagation length as the function of the geometrical parameters of the structure. We have also considered THz field confinement by adiabatic increase of the depth of the grooves. It is shown that the finite skin depth limits the propagation length of spoof plasmons as well as a possibility to localize THz field. Geometrical parameters of the structure are found which provide optimal guiding and localization of THz energy.