1,721,067 research outputs found
Study of the interaction potential between He and a self-assembled monolayer of decanethiol
No full textOxygen adsorption on graphite and nanotubes
No full textWe study the binding of molecular oxygen to a graphene sheet and to a (8,0) single walled carbon nanotube, by means of spin-unrestricted density-functional calculations. We find that triplet oxygen retains its spin-polarized state when interacting with graphene or the nanotube. This leads to the formation of a weak bond with essentially no charge transfer between the molecule and the sheet or tube, as one would expect for a physisorptive bond. This result is independent on the approximation used for the exchange-correlation functional. The binding strength, however, depends strongly on the functional, reflecting the inability of current approximation functionals to deal correctly with dispersion forces. Gradient-corrected functionals yield very weak binding at distances around 4 Angstrom, whereas local density functional results yield substantially stronger binding for both graphene and the nanotube at distances of less than 3 Angstrom. The picture of oxygen physisorption is not substantially altered by the presence of topological defects such as 5-7 Stone-Wales pairs. (C) 2003 American Institute of Physics
Atomic diffraction study of the interaction of helium atoms with the surface of an organic single crystal: the (001) cleavage planes of guanidinium methanesulfonate
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Helium diffraction study of organic single crystal surfaces: hydrogen-bonded and methyl-terminated (001) cleavage planes of a guanidinium methanesulfonate crystal
No full textInteraction of Hydrogen Atoms with Polyatomic Molecules Studied by Means of Scattering Experiments and Hybrid Hartree-Fock Plus Damped Dispersion Calculations.
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Coverage-dependent adsorption of CH3S and (CH3S)(2) on Au(111): A density functional theory study
No full textThe origin of the superlattice present in the commensurate hexagonal structure of self-assembled monolayers of n-alkanethiols on gold and the question of whether the thiols are adsorbed onto the surface as dimers (disulfides) or monomers (thiolates) have been under debate for many years. Looking for a better understanding of the structural properties of these systems, we have performed a theoretical study of the molecular and dissociative adsorption of dimethyl disulfide on Au(111) as a function of coverage (0.25 less than or equal to Theta less than or equal to 1), using gradient-corrected density functional (DFT) calculations with a slab geometry. For the dissociated state, our results indicate that the hcp hollow site is much less favorable than the fee site. For the latter site, we find that, because of surface gold atom relaxation, the adsorption energy depends strongly on Theta, changing from similar to 18 kcal/mol at Theta = 0.25 to similar to3 kcal/mol at Theta = 1. For the bridge site, instead, the adsorption energy is a weak function of Theta, and for all investigated coverages, this site is by far the most stable. According to our DFT approach, the adsorption of dimethyl disulfide is dissociative with a thermodynamic gain, at Theta = 1, of similar to 13 kcal/mol with respect to the adsorbed molecular state. We also find, however, that the energy of c(4 x 2) structures containing at least two inequivalent CH3S groups per unit cell (with a minimum S-S distance of similar to3.7 Angstrom) is, within the accuracy of our approach, indistinguishable from the pure (root3 x root3) hexagonal structure. Our results suggest that the full solution of this thorny problem will require, also for the shortest chains, an estimate of the energetic contribution of dispersion forces that are not included in the DFT calculations
Ultrasensitive protein detection in nano-immuno assays based on DNA directed immobilization and atomic force microscopy nanografting
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