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The Fischer-Tropsch reaction is initiated by direct CO dissociation for Iron catalyst even though a H-assisted mechanism may be easier on other metals. In the gas phase, the CO dissociation is only favorable for Fe-clusters composed by more than 11 atoms. We show here the remarkable effect of the support TiO 2 (1 1 0), making this dissociation exothermic for Fe 4 and Fe 5 clusters. The main factor for the CO activation is the electron transfer to the reducible support. The role of the TiO 2 (1 1 0) support is to transform the neutral cluster into a positively charged one for which CO dissociation is easier. [ABSTRACT FROM AUTHOR]

Abstract: X-ray photoelectron spectroscopy and transmission electron microscopy have been used to investigate the nature and characteristics of oxygen deficient gallium oxide films grown by pulsed laser deposition. The presence of the Ga3+ and Ga+ oxidation states, together with metallic Ga0 was observed by XPS in Ga2O2.3 sub-oxide films. TEM images reveal the presence in a Ga2O3 matrix of gallium oblong particles whose structure studied at nitrogen temperature was found to correspond to the β monoclinic phase of metallic gallium. These results characterize the formation of nanocomposite films with Ga metallic clusters embedded in a stoichiometric Ga2O3 matrix. The nanocomposite film formation is due to a phase separation in the metastable sub-stoichiometric Ga2O2.3 film. [Copyright &y& Elsevier]

Abstract: The dipole moments of Na n clusters in the size range 10< n <20, recently measured at very low temperature (20K), are much smaller than predicted by standard density functional methods. On the other hand, the calculated static dipole polarizabilities in that range of sizes deviate non-systematically from the measured ones, depending on the employed first principles approach. In this work we calculate the dipole moments and polarizabilities of a few isomers of Na n clusters of selected sizes (n =13, 14, 16), obtained recently through an extensive unbiased search of the global minimum structures, and using density functional theory methods as well as ab initio MP2, CASSCF, and MR-CI methods. Among the density functional approaches, we consider the usual local density and generalized gradient approximations, as well as a recent van der Waals self-consistent functional accounting for non-local dispersion interactions. Both non-local pseudopotentials and all-electron implementations are employed and compared in order to assess the possible contribution of the core electrons to the electric dipole moments. Our new geometries possess significantly smaller electric dipole moments than previous density functional results, mostly when combined with the van der Waals exchange–correlation functional. However, although the agreement with experiment clearly improves upon previous calculations, the theoretical dipole moments are still about one order of magnitude larger than the experimental values, suggesting that the correct global minimum structures have not been located yet. [Copyright &y& Elsevier]

Abstract: A magnetron-sputtering (MagS) cluster source was used to produce metal clusters of different size distributions by varying individual source parameters. Selectivity of the size of the Al clusters was observed and the mass distribution presents wide-range controllability by the MagS-source, which enables experimental determination of the growth process of Al clusters. By implementing the extended Smoluchowski rate equation, here we propose an interpretation of the cluster-growth kinetics in the gas phase environment. A collision-dependent growing time domain is demonstrated. [Copyright &y& Elsevier]

Abstract: Highly non-stoichiometric indium tin oxide (ITO) thin films were grown by pulsed energy beam deposition (pulsed laser deposition-PLD and pulsed electron beam deposition-PED) under low oxygen pressure. The analysis of the structure and electrical transport properties showed that ITO films with a large oxygen deficiency (more than 20%) are nanocomposite films with metallic (In, Sn) clusters embedded in a stoichiometric and crystalline oxide matrix. The presence of the metallic clusters induces specific transport properties, i.e. a metallic conductivity via percolation with a superconducting transition at low temperature (about 6K) and the melting and freezing of the In–Sn clusters in the room temperature to 450K range evidenced by large changes in resistivity and a hysteresis cycle. By controlling the oxygen deficiency and temperature during the growth, the transport and optical properties of the nanocomposite oxide films could be tuned from metallic-like to insulating and from transparent to absorbing films. [Copyright &y& Elsevier]

Abstract: An influence of metallic clusters on the optical absorption and phonon spectra of crystals was studied. Metallic clusters of spherical shape were formed during the growth of non-stoichiometric crystals. Radii of clusters are in range from 10 to 500nm according to scanning electron microscopy (SEM) data. The density of clusters was estimated from fractal dimension calculations. The fractal dimension of clusters has been found to be varied from 1.488 to 1.793. In the framework of Mie theory the spectral and size dependencies of extinction coefficients were calculated. From the experimentally obtained spectra it is evident that the metallic clusters are responsible for the bands in the transparency region of crystals (360–430nm) and for the peaks in the mid-infrared absorption spectra which are not present in the spectra of pure cadmium iodide. The nature of this additional optical and infrared absorption is concerned with the bulk and surface plasmons and the surface phonon modes of metallic clusters, respectively. [Copyright &y& Elsevier]

Abstract: We present a theoretical study of embedded in- and on the surface of a rare-gas droplet. We describe the active electrons of the cluster using time-dependent density functional theory, while the surrounding Ar atoms are treated by classical molecular dynamics of polarizable atoms. Like for neutral clusters, we found that the surrounding material modifies noticeably the optical properties of compared to the free cluster. Ar polarization and core repulsion act in opposite directions, so that the actual line shift depends significantly on the trapping site. We show that the long range monopole-dipole coupling between a charged cluster and a polarizable matrix makes more likely to be embedded inside the Ar matrix, while small neutral Na clusters are more likely to be trapped at the surface. [Copyright &y& Elsevier]

The structure and electrical properties of laser-ablated LaSrMnO thin films containing mesoscopic clusters with metallic conductivity in an insulator matrix were studied. It is shown that the film properties, including temperature dependence of magnetoresistance and its behavior in high magnetic field, display features typical for spin-dependent tunneling. [Copyright &y& Elsevier]

[Display omitted] • Ground state structures were obtained from BOMD and DFT calculations. • The Li 12 Y system is a new superatom with a high magnetic moment and exchange splitting with icosahedral geometry. • (Li 12 Y) 2 dimer preserves the energetic and magnetic stability. • The Boltzmann distribution shows the dependence between magnetic properties and temperature. A study was carried out to determine the structural, energetic, and magnetic properties of lithium clusters doped with yttrium, including Born − Oppenheimer molecular dynamics under the Density Functional Theory framework. The study considered the ZORA model for the scalar relativistic effects due to the presence of the yttrium atom. The Li 12 Y system was identified as a new superatom with icosahedral geometry, high magnetic moment, and exchange splitting. The interactions of the sp -Li orbitals with the 4d -Y orbitals are fundamental to understand the effects on the studied properties. The spin density was concentrated over the yttrium atom regardless of the size of the cluster. Furthermore, the energetic integrity of the Li 12 Y is preserved in the (Li 12 Y) 2 dimer, attesting to its potential as a magnetic building block for nanostructured materials. Additionally, the effect of temperature on the magnetic moment in the context of classical Boltzmann distribution was explored, finding a dependence between magnetic properties and temperature. [ABSTRACT FROM AUTHOR]