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Available from: Thomas Bligaard, Jul 02, 2015
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    ABSTRACT: We performed a series of density functional theory calculations of dissociative oxygen adsorption on fcc metals and their corresponding rocksalt monoxides to elucidate the relationship between the oxide electronic structure and its corresponding reactivity. We decomposed the dissociative adsorption energy of oxygen on an oxide surface into a sum of the adsorption energy on the metal and a change in adsorption energy caused by both expanding and oxidizing the lattice. We were able to identify the key features of the electronic structure that explains the trends in adsorption energies on 3d transition metal monoxide surfaces.
    Catalysis Communications 07/2014; 52:60–64. DOI:10.1016/j.catcom.2013.10.028 · 3.32 Impact Factor
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    ABSTRACT: We apply standard density functional theory at the generalized gradient approximation (GGA) level to study the stability of rutile metal oxides. It is well known that standard GGA exchange and correlation in some cases is not sufficient to address reduction and oxidation reactions. Especially the formation energy of the oxygen molecule and the electron self-interaction for localized d and f electrons are known shortcomings. In this paper we show that despite the known problems, it is possible to calculate the stability of a wide range of rutile oxides MO(2), with M being Pt, Ru, Ir, Os, Pb, Re, Mn, Se, Ge, Ti, Cr, Nb, W, Mo, and V, using the electrochemical series as reference. The mean absolute error of the formation energy is 0.29 eV using the revised Perdew-Burke-Ernzerhof (PBE) GGA functional. We believe that the reason for the success is due to the reference level being H(2) and H(2)O and not O(2) and due to a more accurate description of exchange for this particular GGA functional compared to PBE. Furthermore, we would expect the self-interaction problem to be largest for the most localized d orbitals; that means the late 3d metals and since Co, Fe, Ni, and Cu do not form rutile oxides they are not included in this study. We show that the variations in formation energy can be understood in terms of a previously suggested model separating the formation energy into a metal deformation contribution and an oxygen binding contribution. The latter is found to scale with the filling of the d band.
    Physical Review B 01/2009; 79:045120. DOI:10.1103/PhysRevB.79.045120 · 3.66 Impact Factor
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    ABSTRACT: The adsorption energy of an adsorbate can depend strongly on its coverage. We present density-functional calculations of the adsorption energy of C, N, and O on the fcc sites of Pd(111) at coverages from 0.2 to 1 ML. The adsorption energy generally increases (gets weaker) with coverage in a near linear fashion for the most stable configurations. We observed a practically constant d-band filling at all coverages and interpret the coverage dependence in terms of a simple d-band model where the d band is broadened and lowered in energy by the interaction with the adsorbates. We find the Pd(111) d-band center is approximately linearly correlated with the coverage of each adsorbate. A consequence of this electronic structure-coverage correlation for each adsorbate is that the adsorption energies of each adsorbate configuration are strongly correlated with each other. All of the exceptions to these correlations can be traced to surface reconstruction or adsorbate configurations that are not geometrically similar to adsorption in the fcc hollow sites. Finally, we show that all the coverage-dependent adsorption energies can be collapsed into a single configurational correlation by scaling of the adsorption energies.
    Physical review. B, Condensed matter 05/2009; 79(20). DOI:10.1103/PhysRevB.79.205412 · 3.66 Impact Factor