Biomedical subjects

K-H Rieder

Publications and source records attributed to K-H Rieder.

3 recordsLinked to original sources

PubMed2002

Atomic-scale structure of dislocations revealed by scanning tunneling microscopy and molecular dynamics.

The intersection between dislocations and a Ag(111) surface has been studied using an interplay of scanning tunneling microscopy (STM) and molecular dynamics. Whereas the STM provides atomically resolved information about the surface structure and Burgers vectors of the dislocations, the simulations can be used to determine dislocation structure and orientation in the near-surface region. In a similar way, the subsurface structure of other extended defects can be studied. The simulations show dislocations to reorient the partials in the surface region leading to an increased splitting width at the surface, in agreement with the STM observations. Implications for surface-induced cross slip are discussed.

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PubMed2002

Engineering electronic lifetimes in artificial atomic structures.

By means of atomic manipulation, 51 Ag atoms have been precisely positioned to form a triangle with a base length of 245 A on a Ag(111) substrate. The scattering of the surface electrons at these adatoms results in a complex interference pattern. Spectroscopic data and dI/dV maps taken inside the triangle have been quantitatively evaluated by multiple scattering calculations of the wave pattern. Adjustment of the scattering parameters to the data yields the properties of the scatterers and the electron lifetimes. The experimental results for the electron lifetimes deviate from a (E-E(F))(-2) dependence and reflect the electronic band structure at the surface as well as the local influence of the triangle.

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PubMed2002

High frequency surface vibrational modes and relaxation of MgO nanocrystals.

We present a computational proof for the puzzling experimental vibrational density of states in MgO nanocrystals measured by neutron scattering. For the first time, the experimental peak of longitudinal optical modes in the high frequency region is theoretically reproduced and traced back to surface inward relaxation. Practically perfect agreement of theory with the experiment demonstrates the importance of nanocrystal size effects. Dependence of the transversal optical model on the volume/surface ratio is also verified. Strong (up to 2%) buckling of nanocrystal faces is found. Our calculations show varieties of relaxation shapes for clusters, shedding light on contradictory data on nanocrystals and infinite surfaces.

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