Showing papers by "Bjørk Hammer published in 1997"
TL;DR: In this article, self-consistent density functional calculations using the LMTO-ASA method of the variations in the surface electronic structure for pseudomorfic overlayers and impurities of Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au on the other metals are presented.
Abstract: We present self-consistent density functional calculations using the LMTO-ASA method of the variations in the surface electronic structure for pseudomorfic overlayers and impurities of Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au on the other metals. Knowledge of these variations is of importance in understanding trends in the reactivity of metal surfaces. A simple model is presented which gives a description of the overall trends in the self-consistently calculated results.
1,061 citations
TL;DR: In this article, the structure sensitivity of CO adsorption on different flat, stepped, kinked and reconstructed Pt surfaces was studied using large-scale density-functional calculations, and the authors found an extremely strong structure sensitivity with variations up to 1 eV (or 100%) from one structure to the next.
Abstract: The structure sensitivity of CO adsorption on different flat, stepped, kinked and reconstructed Pt surfaces is studied using large-scale density-functional calculations. We find an extremely strong structure sensitivity in the adsorption energy with variations up to 1 eV (or 100%) from one structure to the next. We propose a model to explain this behavior, and use it to discuss more generally the origin of structure sensitivity in heterogeneous catalysis.
443 citations
TL;DR: In this paper, the structure and bonding in small MoS2 structures with and without Co are studied theoretically using self-consistent density functional theory with a non-local exchange-correlation energy.
Abstract: The structure and bonding in small MoS2 structures with and without Co is studied theoretically using self-consistent density functional theory with a non-local exchange-correlation energy. The structures model the catalysts used extensively in hydrotreating. We study in detail the structure and binding energies as a function of the amount of sulfur. The calculations show that extensive reconstructions occur at the two types of MoS2 edges where the sulfur dimerizes and occupies non-lattice positions. These structures are shown to be in good agreement with available experimental data. We also study the energy required to form sulfur vacancies, which are believed to be the active sites for many hydrotreating reactions. The presence of Co atoms at the edges is shown to lead to a significant lowering of the metal-sulfur binding energy. This imposes an increase in the concentration of active sites for the reactions and may thus explain the promoting effect of Co.
144 citations
TL;DR: In this paper, a series of density functional calculations of the adsorption and dissociation of N2on Ru(0001) were performed to understand the ammonia synthesis reaction over Ru-based catalysts.
103 citations
TL;DR: In this article, the adsorption energies, atomic structures and vibrational modes of molecularly chemisorbed states are well reproduced in the present calculations, and the dissociation energy barrier of CO on the Ni(111) surface is much smaller than that on the Pt( 111) surface.
91 citations
01 Jan 1997
TL;DR: The adsorption and further reaction of molecules from the gas or liquid phase on a solid surface is a very common phenomenon as discussed by the authors, and all solid surfaces have varying amounts of adsorbed gases in air.
Abstract: The adsorption and further reaction of molecules from the gas or liquid phase on a solid surface is a very common phenomenon. All solid surfaces have varying amounts of adsorbed gases in air, and adsorption and chemical reactions at surfaces form the basis of a large number of technically important processes ranging from corrosion to heterogeneous catalysis.
82 citations
TL;DR: In this article, the interaction of NO with the stepped Pd(211) surface was studied using density functional theory slab calculations, and it was shown that surface sites are not populated in a sequential manner as the NO coverage is increased.
Abstract: The interaction of nitric oxide, NO, with the stepped Pd(211) surface is studied using density functional theory slab calculations. Calculated chemisorption energies and geometries reveal that surface sites are not populated in a sequential manner as the NO coverage is increased. This comes about through mutual NO interactions that reorganize the adsorbates during the adsorption. The finding of nonsequential site population allows a reinterpretation of existing experimental data.
63 citations
TL;DR: The subject of hydrogen diffusion on metal surfaces has been a subject of great interest, both theoretically and experimentally, due to the pronounced quantum behavior at low temperatures as mentioned in this paper, and has been studied extensively in the literature.
Abstract: Hydrogen diffusion on metal surfaces has been a subject of great interest, both theoretically and experimentally, due to the pronounced quantum behavior at low temperatures.
50 citations
TL;DR: In this paper, the authors untersuchten die Adsorption von N, and CO auf Ru(OOl) with (,/3X 73)R30o-Struktur mittels Dichtefunktionalmethoden.
Abstract: Es wurde die Adsorption von N, und CO auf Ru(OOl) mit (,/3X 73)R30o-Struktur mittels Dichtefunktionalmethoden untersucht. Die berechneten Schwingungsfrequenzen, die Geometrie und die Adsorptionsstrategien stimmen für beide Système gut mit experimentellen Ergebnissen überein. Wir erklaren die groBen Unterschiede in den Adsorptionsenergien mit Hilfe einer einfachen Modellbetrachtung, die die Kopplung zwischen den Ru dZustanden und den molekularen 2 (1 ,.)und 5 a(3af)-Zustánáen berücksichtigt.
25 citations
TL;DR: In this article, a plane-wave pseudopotential calculation based on density-functional theory at the local density approximation level was performed to investigate all the possible structures which are permitted by the known crystal symmetry.
Abstract: Using plane-wave pseudopotential calculations based on density-functional theory at the local-density-approximation level we investigate all the possible \ensuremath{\kappa}-${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$ structures which are permitted by the known crystal symmetry. We find that structures with sixfold coordinated Al atoms are significantly more stable than those having any or all of the Al atoms in fourfold coordinated sites. This is in agreement with preliminary experimental results.
17 citations