@misc{ToepferTremblay2016,
  author    = {T{\"o}pfer, Kai and Tremblay, Jean Christophe},
  title     = {How surface reparation prevents catalytic oxidation of carbon monoxide on atomic gold at defective magnesium oxide surfaces},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-394978},
  pages     = {8},
  year      = {2016},
  abstract  = {In this contribution, we study using first principles the co-adsorption and catalytic behaviors of CO and O2 on a single gold atom deposited at defective magnesium oxide surfaces. Using cluster models and point charge embedding within a density functional theory framework, we simulate the CO oxidation reaction for Au1 on differently charged oxygen vacancies of MgO(001) to rationalize its experimentally observed lack of catalytic activity. Our results show that: (1) co-adsorption is weakly supported at F0 and F2+ defects but not at F1+ sites, (2) electron redistribution from the F0 vacancy via the Au1 cluster to the adsorbed molecular oxygen weakens the O2 bond, as required for a sustainable catalytic cycle, (3) a metastable carbonate intermediate can form on defects of the F0 type, (4) only a small activation barrier exists for the highly favorable dissociation of CO2 from F0, and (5) the moderate adsorption energy of the gold atom on the F0 defect cannot prevent insertion of molecular oxygen inside the defect. Due to the lack of protection of the color centers, the surface becomes invariably repaired by the surrounding oxygen and the catalytic cycle is irreversibly broken in the first oxidation step.},
  language  = {en}
}
@misc{TremblayBlancoRey2015,
  author    = {Tremblay, Jean Christophe and Blanco-Rey, Maria},
  title     = {Manipulating interfacial hydrogens at palladium via STM},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-99511},
  pages     = {11},
  year      = {2015},
  abstract  = {In this contribution, we provide a detailed dynamical analysis of the interfacial hydrogen migration mediated by scanning tunneling microscopy (STM). Contributions from the STM-current and from the non-adiabatic couplings are taken into account using only first principle models. The slight asymmetry of the tunnelling rates with respect to the potential bias sign inferred from experimental observations is reproduced by weighting the contributions of the metal acceptor-donor states for the propagation of the impinging electrons. The quasi-thermal inelastic collision mechanism is treated perturbatively. The influence of hydrogen pre-coverage is also investigated using new potential energy surfaces obtained from periodic density functional theory calculations. Fully quantum dynamical simulations of the system evolution are performed by solving the Pauli master equation, providing insight into the reaction mechanism of STM manipulation of subsurface hydrogens. It is observed that the hydrogen impurity favors resurfacing over occupation of the bulk and subsurface sites whenever possible. The present simulations give strong indication that the experimentally observed protuberances after STM-excitation are due to hydrogen accumulating in the vicinity of the surface.},
  language  = {en}
}