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Journal ArticleDOI

Chemisorption geometry of O at the Ni(100)-surface

01 Oct 1988-Physica Scripta (IOP Publishing)-Vol. 38, Iss: 4, pp 594-599
TL;DR: In this article, the position and chemisorption energy of O on Ni(100) as a function of coverage and including atomic relaxations were studied. But the results do not indicate the pseudo-bridge position as a stable one.
Abstract: We study the position and chemisorption energy of O on Ni(100) as a function of coverage and including atomic relaxations. A Hubbard like tight-binding Hamiltonian and the Hartree-Fock approximation is used. The repulsive interaction between atoms is described by a Born-Mayer type potential. Results are given for atomic relaxations and for the binding energy of O at various chemisorption sites. Our results do not indicate the pseudo-bridge position as a stable one.
Citations
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Journal ArticleDOI
TL;DR: In this paper, a detailed LEED analysis of the p(2 × 2)O/Ni(100) phase was conducted, whereby the purity of the 2 × 2 phase was controlled by HREELS.

49 citations

References
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Journal ArticleDOI
TL;DR: A new theory is presented for describing band gaps and electronic structures of transition-metal compounds and both the metallic sulfides and insulating oxides and halides occur in a quite natural manner.
Abstract: A new theory is presented for describing band gaps and electronic structures of transition-metal compounds. A theoretical phase diagram is presented in which both the metallic sulfides and insulating oxides and halides occur in a quite natural manner.

2,190 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that all interatomic potentials of the classical type (Morse, Lennard-Jones, etc.,) yield, by their very nature, an expansion of the interlayer separation between the topmost surface layers, and that Friedel's tight-binding model for transition metals yields contraction for the (100, (110), and (111) surfaces of a face-centered-cubic transition metal, a result in agreement with experiment.
Abstract: It is shown that all interatomic potentials of the classical type---Morse, Lennard-Jones, etc.,---yield, by their very nature, an expansion of the interlayer separation between the topmost surface layers. No such prediction can be made a priori for the oscillatory-type potentials. Using a simple procedure to compute the relaxations, we also show that Friedel's tight-binding model for transition metals yields contraction for the (100), (110), and (111) surfaces of a face-centered-cubic transition metal, a result in agreement with experiment.

601 citations

Journal ArticleDOI
Abstract: The chemisorption energy of simple gases on transition metals follows some remarkable systematic trends. We construct a simple theory which leads to an understanding of the observed trends and relates the chemisorption energy to the essential parameters characterizing the transition metals, viz., the mean energy of their density of states, the bandwidth, and the number of $d$ electrons. The theory is applied to the adsorption of hydrogen and oxygen on $3d$ and $4d$ transition metals. The positions of the atomic levels of hydrogen and oxygen (and nitrogen) with respect to the $d$ bands of the transition metals is such that the primary binding comes from transfer of $d$ electrons from surface metal atoms to the adatoms and to low-energy bonding resonances induced in the metal atoms. However, there is large enough hybridization of the adatom orbitals with the surface metal-atom orbitals that the local density of states of the metal atoms is significantly altered throughout the band. Correspondingly the metal parameters that determine the binding energy are the average position of the $d$ band with respect to the adatom orbital energy and the overall width of the $d$ band.

145 citations

Journal ArticleDOI
TL;DR: In this article, it is shown that whereas Friedel's d bond contribution is primarily responsible for the cohesive energy, the s electrons are crucial for providing the repulsive pressure to counter the attractive d contribution at the equilibrium atomic volume.
Abstract: For pt.II see ibid., vol.7, p.1009 (1978). The s and d contributions to the pressure and bulk modulus across the series and as a function of volume are presented using Pettifor's partial pressure expression and the results of part I of this series on the behaviour of the energy bands. It is shown that whereas Friedel's d bond contribution is primarily responsible for the cohesive energy, the s electrons are crucial for providing the repulsive pressure to counter the attractive d contribution at the equilibrium atomic volume. Moreover, because of ion core orthogonality constraints, the s electrons determine the bulk modulus away from the noble metal end of the series. The hybridisation contribution is included by assuming it to be proportional to the d resonant width. The cohesive energy is predicted to better than about 10%, the equilibrium atomic volume to 25%, and the bulk modulus (excluding Pd and Ag) to better than 20% across the 4d series. The importance of the neglected second-order contributions such as three-centre integrals is demonstrated.

112 citations

Journal ArticleDOI
TL;DR: In this paper, generalized valence-bond calculations suggest that atomic oxygen chemisorbed on Ni(100) leads to two distinct low-lying states: (1) the radical state with ${R}_{\ensuremath{\perp}}=0.88$ \AA{} and (2) the surface oxide state with
Abstract: Generalized valence-bond calculations suggest that atomic oxygen chemisorbed on Ni(100) leads to two distinct low-lying states: (1) the radical state with ${R}_{\ensuremath{\perp}}=0.88$ \AA{} and ${\ensuremath{\omega}}_{\ensuremath{\perp}}=55$ meV and (2) the surface oxide state with ${R}_{\ensuremath{\perp}}=0.26$ \AA{} and ${\ensuremath{\omega}}_{\ensuremath{\perp}}=38$ meV. We suggest that the radical state dominates for $p(2\ifmmode\times\else\texttimes\fi{}2)$ and that the oxide state dominates for $c(2\ifmmode\times\else\texttimes\fi{}2)$. We find that atomic H, Cl, and S lead to only one low-lying state.

87 citations