Biomedical subjects

Z Sljivancanin

Publications and source records attributed to Z Sljivancanin.

6 recordsLinked to original sources

PubMed2006

Clustering of chemisorbed H(D) atoms on the graphite (0001) surface due to preferential sticking.

We present scanning tunneling microscopy experiments and density functional theory calculations which reveal a unique mechanism for the formation of hydrogen adsorbate clusters on graphite surfaces. Our results show that diffusion of hydrogen atoms is largely inactive and that clustering is a consequence of preferential sticking into specific adsorbate structures. These surprising findings are caused by reduced or even vanishing adsorption barriers for hydrogen in the vicinity of already adsorbed H atoms on the surface and point to a possible novel route to interstellar H2 formation.

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PubMed2006

Metastable structures and recombination pathways for atomic hydrogen on the graphite (0001) surface.

We present scanning tunneling microscopy results which reveal the existence of two distinct hydrogen dimer states on graphite basal planes. Density functional theory calculations allow us to identify the atomic structure of these states and to determine their recombination and desorption pathways. Direct recombination is only possible from one of the two dimer states. This results in increased stability of one dimer species and explains the puzzling double peak structure observed in temperature programmed desorption spectra for hydrogen on graphite.

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PubMed2006

Chiral recognition of organic molecules by atomic kinks on surfaces.

Two distinct non-mirror-symmetric conformations of D- and L-cysteine were found after adsorption on Au(17 11 9)S. This demonstrates chiral heterorecognition, i.e., enantioselectivity of S kinks on vicinal Au(111). The structures as determined by angle scanned x-ray photoelectron diffraction agree well with those from density functional theory calculations. The calculations predict adsorption energies of approximately 2 eV where D-cysteine binds 140 meV stronger than L-cysteine. The classical three point contact model for molecular recognition fails to explain these findings.

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PubMed2003

Supported fe nanoclusters: evolution of magnetic properties with cluster size.

Using a density functional approach, we study structural and magnetic properties of small Fe(n) clusters (n<or=8) deposited on a MgO(100) substrate. Upon deposition, the clusters closely preserve their gas-phase structure. The magnetic moments for the adsorbed clusters exceed the value for bulk Fe. Compared to the gas phase, significant reductions in the magnetic moments are found for Fe(n) clusters with n<or=6. These reductions result from intracluster charge rearrangements caused by interaction with O 2p orbitals, rather than from structural deformations or charge transfer from the surface. As the cluster size increases, the gas-phase magnetic moments are recovered.

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PubMed2001

Distinct reaction mechanisms in the catalytic oxidation of carbon monoxide on Rh(110): scanning tunneling microscopy and density functional theory studies.

By means of scanning tunneling microscopy measurements and density functional theory calculations, we identify the reaction mechanism for the oxidation of carbon monoxide to carbon dioxide on the Rh(110) surface at 160 K, which appears to be completely different than the one active at room temperature. The reasons for these different behaviors are determined. Our results demonstrate that even for a very simple catalytic reaction, the microscopic mechanism can dramatically change with temperature, following pathways that differ for nucleation sites and surface propagation and involve different surface moieties.

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PubMed2001

Oxygen dissociation at Pt steps.

Using scanning tunneling microscopy, thermal energy atom scattering, and density functional theory we have characterized O (2) dissociation on Pt(111) stepped surfaces at the atomic scale. The most reactive site is at the top of the Pt steps. In both the molecular precursor state (MPS) and the transition state (TS), the O (2) has its axis aligned parallel to the step edge. Controlled step decoration with Ag monatomic chains was used to locally tune the reactivity of Pt step sites. The enhanced reactivity at the Pt step sites is not caused by a decrease of the local dissociation barriers from the MPS but is related to a stabilization of both the MPS and TS.

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