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  • The Effect of Hydrogen on the Magnetic Properties of Supported Nano Scale Clusters
  • Meistara
  • We have calculated the structure and magnetic properties of nano scale iron clusters on a
    Cu surface with and without adsorbed hydrogen. The goal was to see what effect hydrogen
    has on the magnetic properties. The calculations were carried out with plane wave based
    density functional theory (DFT) and with the tight-binding Anderson model. The
    adsorption sites for hydrogen atoms were found using the simulated annealing technique.
    We considered a number of configurations differing in the number of hydrogen atoms and
    in their positions. Two trends were found. Firstly, each successive hydrogen atom reduces
    the total magnetic moment of the cluster. Secondly, the strength of the effect depends on
    the position of adsorbed hydrogen atom, namely the number of nearest iron neighbors is
    important. To explain these effects we used Bader analysis in order to decompose the
    charge density of the system and examine the change in electronic density at the iron
    atoms. It was found that hydrogen atom affects only the nearest neighbors and attracts the
    same number of electrons irrespectively of the adsorption site. However, the more iron
    atoms the hydrogen atom is bound to, the weaker the decrease of the total magnetic
    moment of the cluster. We also calculated the density of states for d-electrons of individual
    iron atoms and observed changes near the Fermi level as hydrogen is added. The Anderson
    model contains only three parameters which were selected using information found from
    the analysis of the DFT calculations. The model then could reproduce the DFT results
    quite well.

  • 22.2.2010

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