Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Adsorption of benzene on Si(100) from first principles  [PDF]
Pier Luigi Silvestrelli,Francesco Ancilotto,Flavio Toigo
Physics , 2000, DOI: 10.1103/PhysRevB.62.1596
Abstract: Adsorption of benzene on the Si(100) surface is studied from first principles. We find that the most stable configuration is a tetra-$\sigma$-bonded structure characterized by one C-C double bond and four C-Si bonds. A similar structure, obtained by rotating the benzene molecule by 90 degrees, lies slightly higher in energy. However, rather narrow wells on the potential energy surface characterize these adsorption configurations. A benzene molecule impinging on the Si surface is most likely to be adsorbed in one of three different di-$\sigma$-bonded, metastable structures, characterized by two C-Si bonds, and eventually converts into the lowest-energy configurations. These results are consistent with recent experiments.
First principles study of the adsorption of C60 on Si(111)  [PDF]
Daniel Sanchez-Portal,Emilio Artacho,J. I. Pascual,J. Gomez-Herrero,Richard M. Martin,Jose M. Soler
Physics , 2000, DOI: 10.1016/S0039-6028(00)01008-6
Abstract: The adsorption of C60 on Si(111) has been studied by means of first-principles density functional calculations. A 2x2 adatom surface reconstruction was used to simulate the terraces of the 7x7 reconstruction. The structure of several possible adsorption configurations was optimized using the ab initio atomic forces, finding good candidates for two different adsorption states observed experimentally. While the C60 molecule remains closely spherical, the silicon substrate appears quite soft, especially the adatoms, which move substantially to form extra C-Si bonds, at the expense of breaking Si-Si bonds. The structural relaxation has a much larger effect on the adsorption energies, which strongly depend on the adsorption configuration, than on the charge transfer.
Is silicene stable in air?-First principles study of oxygen adsorption and dissociation on silicene  [PDF]
G. Liu,X. L. Lei,M. S. Wu,B. Xu,C. Y. OuYang
Physics , 2013,
Abstract: The oxygen adsorption and dissociation on pristine silicene surface are studied by use of first-principles in this letter. The oxygen adsorption and dissociation on pristine silicene surface are studied by use of first-principles in this letter. It is found that the pristine silicene is not stable in air because the oxygen molecule can be easily adsorbed and dissociated into two O atoms without overcoming any energy barrier on pristine silicene surface. In addition, dissociated oxygen atoms are relatively difficult to migrate on or desorbed from pristine silicene surface, leading to poor mobility of oxygen atom. As a result, silicene would be changed into Si-O compounds in air. The work will be helpful to reveal the detail of the interaction between oxygen molecules and pristine silicene surface, especially helpful to understand the stability of silicene in air.
A study of Mg adsorption on Si(001) surface from first principles  [PDF]
R. Shaltaf,E. Mete,?. Ellialt?o?lu
Physics , 2003, DOI: 10.1103/PhysRevB.69.125417
Abstract: First-principles calculations using density functional theory based on norm-conserving pseudopotentials have been performed to investigate the Mg adsorption on the Si(001) surface for 1/4, 1/2 and 1 monolayer coverages. For both 1/4 and 1/2 ML coverages it has been found that the most favorable site for the Mg adsorption is the cave site between two dimer rows consistent with the recent experiments. For the 1 ML coverage we have found that the most preferable configuration is when both Mg atoms on 2x1 reconstruction occupy the two shallow sites. We have found that the minimum energy configurations for 1/4 ML coverage is a 2x2 reconstruction while for the 1/2 and 1 ML coverages they are 2x1.
First-principles studies of the adsorption of O2 on Al (001)
Fangying Zhang,Shenglong Zhu,Yingyuan Teng
Chinese Science Bulletin , 2004, DOI: 10.1007/BF03184312
Abstract: The bonding and electronic structures of oxygen molecules adsorbed on Al (001) are theoretically investigated from first-principles using the density functional theory within the generalization gradient approximation (GGA) and a supercell approach. The surface is described by means of a 2 × 2 cell with a thickness of fourteen layers, which consist of 9 layers of Al atoms and 5 layers of vacuum. Oxygen molecules are situated on Al surface. The calculated results indicate that oxygen molecules with their axes parallel to the Al surface are the energetically easiest to be adsorbed on Al (001), while those vertical to the Al surface are the most difficult. There are two different processes for the adsorption of oxygen molecules on Al (001), which are O2→(O2)2 →2O →2O2 and O2→(O2) →O2 +O, and their occurrences are strongly dependent on the initial morphologies.
First-principles calculations for the adsorption of water molecules on the Cu(100) surface  [PDF]
Sanwu Wang,Yanzhao Cao,P. A. Rikvold
Physics , 2004, DOI: 10.1103/PhysRevB.70.205410
Abstract: First-principles density-functional theory and supercell models are employed to calculate the adsorption of water molecules on the Cu(100) surface. In agreement with the experimental observations, the calculations show that a H2O molecule prefers to bond at a one-fold on-top (T1) surface site with a tilted geometry. At low temperatures, rotational diffusion of the molecular axis of the water molecules around the surface normal is predicted to occur at much higher rates than lateral diffusion of the molecules. In addition, the calculated binding energy of an adsorbed water molecule on the surfaces is significantly smaller than the water sublimation energy, indicating a tendency for the formation of water clusters on the Cu(100) surface.
The shortcomings of semi-local and hybrid functionals: what we can learn from surface science studies  [PDF]
A. Stroppa,G. Kresse
Physics , 2008, DOI: 10.1088/1367-2630/10/6/063020
Abstract: A study of the adsorption of CO on late 4d and $5d$ transition metal (111) surfaces (Ru, Rh, Pd, Ag, Os, Ir, and Pt) considering atop and hollow site adsorption is presented. The applied functionals include the gradient corrected PBE and BLYP functional, and the corresponding hybrid Hartree-Fock density functionals HSE and B3LYP. We find that PBE based hybrid functionals (specifically HSE) yield, with the exception of Pt, the correct site order on all considered metals, but they also considerably overestimate the adsorption energies compared to experiment. On the other hand, the semi-local BLYP functional and the corresponding hybrid functional B3LYP yield very satisfactory adsorption energies and the correct adsorption site for all surfaces. We are thus faced with a Procrustean problem: the B3LYP and BLYP functionals seem to be the overall best choice for describing adsorption on metal surfaces, but they simultaneously fail to account well for the properties of the metal, vastly overestimating the equilibrium volume and underestimating the atomization energies. Setting out from these observations, general conclusions are drawn on the relative merits and drawbacks of various semi-local and hybrid functionals. The discussion includes a revised version of the PBE functional specifically optimized for bulk properties and surface energies (PBEsol), a revised version of the PBE functional specifically optimized to predict accurate adsorption energies (rPBE), as well as the aforementioned BLYP functional. We conclude that no semi-local functional is capable to describe all aspects properly, and including non-local exchange also only improves some, but worsens other properties.
First-Principles Calculation of Be(0001) Thin Films: Quantum Size Effect and Adsorption of Atomic Hydrogen  [PDF]
Ping Zhang,Hong-Zhou Song
Physics , 2007,
Abstract: We have carried out first-principles calculations of Be(0001) thin films to study the oscillatory quantum size effects exhibited in the surface energy, work function, and binding energy of the atomic hydrogen monolayer adsorption. The prominent enhancement of the surface density of states at the Fermi level makes Be(0001) thin films more metallic compared to the crystalline Be. As a result, the calculated energetics of Be films and the properties of atomic H adsorption onto Be(0001) surface are featured by a quantum oscillatory behavior. Furthermore, The prominent change in the Be(0001) surface electronic structure by the atomic hydrogen adsorption has also been shown.
Influence of Pb adatom on adsorption of oxygen molecules on Pb(111) surface: a first-principles study

Yang Yu,

中国物理 B , 2010,
Abstract: Using first-principles calculations, we systematically study the influence of Pb adatom on the adsorption and the dissociation of oxygen molecules on Pb(111) surface, to explore the effect of a point defect on the oxidation of the Pb(111) surface. We find that when an oxygen molecule is adsorbed near an adatom on the Pb surface, the molecule will be dissociated without any obvious barriers, and the dissociated O atoms bond with both the adatom and the surface Pb atoms. The adsorption energy in this situation is much larger than that on a clean Pb surface. Besides, for an adsorbed oxygen molecule on a clean Pb surface, a diffusing Pb adatom can also change its adsorption state and enlarge the adsorption energy for O, but it does not make the oxygen molecule dissociated. And in this situation, there is a molecule-like PbO2 cluster formed on the Pb surface.
First Principles Study of Carbon Monoxide Adsorption on Zirconia-Supported Copper  [PDF]
Eric J. Walter,Steven P. Lewis,Andrew M. Rappe
Physics , 1999,
Abstract: We have calculated the adsorption energy of carbon monoxide on a monolayer of copper adsorbed on the (111) face of cubic zirconia. We investigate the structural parameters of three phases of bulk zirconia (cubic, tetragonal, and monoclinic) and find excellent agreement with experiment. We have also analyzed the structural relaxation of both the stoichiometric and reduced (111) surfaces of cubic zirconia ($c$-ZrO$_2$). For adsorption of copper on $c$-ZrO$_2$, we find that the preferred binding site is atop the terminal oxygen atom, favored by 0.3 eV over other high symmetry sites. We compare CO adsorption on zirconia-supported copper to the results of carbon monoxide on copper (100) (S. P. Lewis and A. M. Rappe, J. Chem. Phys. {\bf 110}, 4619,(1999).) and show that adsorption on oxide-supported copper is over 0.2 eV more stable than adsorption on the bare surface.
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.