Biomedical subjects

Javier Fdez Sanz

Publications and source records attributed to Javier Fdez Sanz.

4 recordsLinked to original sources

PubMed2006

Unravelling the origin of the high-catalytic activity of supported Au: a density-functional theory-based interpretation.

Using first principles DF calculations we have studied the structural and catalytic properties of Au supported on TiOx-Mo(112) films. Our theoretical models are consistent with an initial (8 x 2) Mo(112)-Ti2O3 pattern which after Au deposition gives rise to ordered Au films that completely wet the surface. The oxidation of CO on model surfaces at coverage 1, 4/3, and 5/2 ML has been analyzed. The oxidation proceeds through a peroxo-like complex in which molecular oxygen is simultaneously bound to the CO and the surface. The energy barrier computed for a Au coverage of 4/3 ML is found significantly lower in agreement with the unusual high activity observed for this catalyst. The detailed analysis of the geometry and electronic structure provides a fundamental understanding of the reaction.

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PubMed2006

The constrained space orbital variation analysis for periodic ab initio calculations.

The constrained space orbital variation (CSOV) method for the analysis of the interaction energy has been implemented in the periodic ab initio CRYSTAL03 code. The method allows for the partition of the energy of two interacting chemical entities, represented in turn by periodic models, into contributions which account for electrostatic effects, mutual polarization and charge transfer. The implementation permits one to carry out the analysis both at the Hartree-Fock and density functional theory levels, where in the latter the most popular exchange-correlation functionals can be used. As an illustrating example, the analysis of the interaction between CO and the MgO (001) surface has been considered. As expected by the almost fully ionic character of the support, our periodic CSOV results, in general agree with those previously obtained using the embedded cluster approach, showing the reliability of the present implementation.

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PubMed2005

Interaction potentials from periodic density-functional theory calculations: molecular-dynamics simulations of Au clusters deposited on the TiN (001) surface.

Molecular-dynamics simulations of gold particles deposited on a TiN (001) surface have been accounted for through classical pair potentials describing the atom force field. The interaction between Ti-N, Ti-Ti, N-N, Au-Au, Au-Ti, and Au-N pairs was estimated by following a procedure in which the interaction energy between two sets of atoms is estimated from density-functional calculations performed with periodic boundary conditions using plane waves as basis set. The pair potentials were expressed as the sum of two contributions: long range in a Coulomb form and a short-range term, which included the rest of the energy contributions. Simulations of the TiN (001) isolated surface reproduced the already described surface relaxation, with a rippling parameter in agreement with that found from a purely first-principles approach. Simulations of gold deposition on such surfaces showed the formation of metal clusters with well-defined fcc structure and epitaxially grown.

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PubMed2005

Mechanism of Cu deposition on the alpha-Al(2)O(3) (0001) surface.

The growth mechanism of the Cu/alpha-Al(2)O(3) (0001) interface is studied by first-principles molecular-dynamics simulations as a function of the transition-metal coverage (theta) and the temperature of the system. On the anhydrous surface growth of Cu(0) 3D clusters is predicted. On the partially hydroxylated surface, a Cu(I) monolayer, relatively stable upon the temperature rising, is first observed (theta<1/3 ML). Increasing Cu loading leads to Cu(I)/Cu(0) mixed phases that when heated aggregate into 3D particles increasing the number of Cu(0) atoms, in agreement with the Auger spectra of Kelber et al.

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