6 research outputs found
Poisoning of Hydrogen Dissociation at Pd (100) by Adsorbed Sulfur Studied by ab initio Quantum Dynamics and ab initio Molecular Dynamics
We report calculations of the dissociative adsorption of H_2 at Pd (100)
covered with 1/4 monolayer of sulfur using quantum dynamics as well as
molecular dynamics and taking all six degrees of freedom of the two H atoms
fully into account. The ab initio potential-energy surface (PES) is found to be
very strongly corrugated. In particular we discuss the influence of tunneling,
zero-point vibrations, localization of the nuclei's wave function when narrow
valleys of the PES are passed, steering of the approaching H_2 molecules
towards low energy barrier configurations, and the time scales of the center of
mass motion and the other degrees of freedom. Several ``established'' concepts,
which were derived from low-dimensional dynamical studies, are shown to be not
valid.Comment: 4 pages, 3 figures, submitted to Surf. Sci. Lett. Other related
publications can be found at http://www.rz-berlin.mpg.de/th/paper.htm
High-dimensional quantum dynamics of adsorption and desorption of H at Cu(111)
We performed high-dimensional quantum dynamical calculations of the
dissociative adsorption and associative desorption of hydrogen on Cu(111). The
potential energy surface (PES) is obtained from density functional theory
calculations. Two regimes of dynamics are found, at low energies sticking is
determined by the minimum energy barrier, at high energies by the distribution
of barrier heights. Experimental results are well-reproduced qualitatively, but
some quantitative discrepancies are identified as well.Comment: 4 two column pages, revtex, 4 figures, to appear in Phys. Rev. Let