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  • American Institute of Physics (AIP)  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Charge separation and covalent bonding in metal oxide surfaces: A local density functional study on the MgO(001) surface (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 6826-6836 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A first principles local density functional investigation on extended, two-dimensional periodic slab models of the MgO(001) surface is performed, using the linear combination of Gaussian-type orbitals (LCGTO) technique as implemented in the FILMS program package. Stimulated by recent theoretical evidence for a reduced charge separation in MgO(001), a detailed analysis of the charge distribution and its influence on the electrical field above the surface is carried out. Two different methods to quantify the charge separation in the ionic substrate are employed, a local one based on the topological atom approach and a global one derived from the Madelung field of the surface near potential adsorbates. Both procedures lead to a charge separation significantly (10%–20%) below the nominal ionic value of ±2 a.u. A variational atomic orbital analysis is utilized to discuss the origin of the Mg 3s and 3p structures discernible in the crystal orbitals of the MgO slab systems. They are identified as covalent magnesium valence orbital admixtures to the oxygen dominated valence bands in consistence with the reduced charge separation. Their influence on the cohesive energy of crystalline MgO, however, is found to be only 5% (∼0.5 eV).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467042
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  • 2
    Electronic Resource
    Electronic Resource
    Interpretation of x-ray emission spectra: NO adsorbed on Ru(001) (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 4704-4713 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A density functional investigation of the x-ray emission spectrum of NO adsorbed on Ru(001) has been carried out using model cluster calculations. The dipole matrix elements governing the emission probability were evaluated in the frozen ground-state approximation. The resulting simulated spectra exhibit all characteristic features of the experimental data. A detailed analysis of the electronic structure of the model clusters permits a complete rationalization of all observed trends. Furthermore, a picture of the surface chemical bond results in which the classical Blyholder frontier orbital model is extended to a three-orbital description for both the π and σ interactions. Comparison of different adsorption sites reveals that threefold coordinated NO features a stronger orbital interaction with the substrate than NO adsorbed in an on-top position. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479232
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  • 3
    Electronic Resource
    Electronic Resource
    Density functional investigation of the geometric and electronic structure of ethylene adsorbed on Si(001) (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 9868-9876 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A detailed first-principles density functional analysis of the geometric and electronic properties of ethylene adsorbed on the dimer reconstructed Si(001)-(2×1) surface is presented. This theoretical study was carried out in close reference to a recent angle-resolved photoemission spectroscopy investigation of the same adsorption system. Adsorbate weighted Kohn-Sham one-particle spectra are calculated and compared to the band structure derived from the angle-resolved photoemission spectra. In addition, the symmetry character of the concomitant Bloch waves is determined to yield information which can directly be related to the results of a dipole selection rule analysis of the corresponding photoemission signals. Total energy minimization of a model slab reveals a distortion of the adsorption complex at saturation coverage to local C2 symmetry involving an 11° rotation of the ethylene molecule around the surface normal and a 27° twist of the methylene groups around the CC axis. This finding is confirmed by a comparison of the calculated band dispersions with those found in the angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) experiments. The driving forces for the distortion of the adsorption complex can be traced to direct Pauli repulsion between the hydrogen atoms of neighboring ethylene molecules and to a bonding overlap contribution from the ethylene 1b2g-derived orbitals of the adlayer. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476425
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  • 4
    Electronic Resource
    Electronic Resource
    The adsorption of acetylene on Ni(110): An experimental and theoretical study (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 9709-9724 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The adsorption of acetylene on Ni(110) was investigated by temperature programmed desorption (TPD), low energy electron diffraction (LEED), angle resolved ultraviolet-photoelectron spectroscopy (ARUPS), and near edge x-ray absorption fine structure (NEXAFS) measurements, as well as by detailed model cluster calculations and slab model band structure calculations. By combining the experimental results and those of the cluster studies an orientation of the molecules is deduced with the C–C axis parallel to the surface and preferentially aligned along the substrate troughs ([11¯0] azimuth) as well as with a highly coordinated adsorption site in the substrate troughs. A detailed analysis of the photoemission spectrum is given. The proposed adsorption geometry is corroborated by band structure calculations for various alternative sites and orientations that are shown to be very sensitive to the azimuthal orientation of the adsorbed molecules. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468790
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