Ab initioquantum and molecular dynamics of the dissociative adsorption of hydrogen on Pd(100)

Abstract

The dissociative adsorption of hydrogen on Pd͑100͒ has been studied by ab initio quantum dynamics and ab initio molecular-dynamics calculations. Treating all hydrogen degrees of freedom as dynamical coordinates implies a high dimensionality and requires statistical averages over thousands of trajectories. An efficient and accurate treatment of such extensive statistics is achieved in a three-step approach: In a first step we evaluate the ab initio potential-energy surface ͑PES͒ for a number of appropriate points in configuration space. Then ͑as step 2͒ we determine an analytical representation that serves as an interpolation between the actually calculated points. In an independent third step dynamical calculations are performed on the analytical representation of the PES. Thus the dissociation dynamics is investigated without any crucial assumption except for the BornOppenheimer approximation which is anyhow employed when density-functional-theory calculations are performed. The ab initio molecular dynamics is compared to detailed quantum-dynamical calculations on exactly the same ab initio PES. The occurence of quantum oscillations in the sticking probability as a function of kinetic energy is addressed. They turn out to be very sensitive to the symmetry of the initial conditions. At low kinetic energies sticking is dominated by the steering effect, which is illustrated using classical trajectories. The steering effect depends on the kinetic energy, but not on the mass of the molecules, as long as no energy transfer to the substrate atoms is considered. The comparison between quantum and classical calculations of the sticking probability shows the importance of zero-point effects in the hydrogen dynamics. The dependence of the sticking probability on the angle of incidence is analyzed; it is found to be in good agreement with experimental data. The results show that the determination of the potential-energy surface combined with high-dimensional dynamical calculations, in which all relevant degrees of freedom are taken into account, leads to a detailed understanding of the dissociation dynamics of hydrogen at a transition metal surface.

Generation and orientation of organoxenon molecule H–Xe–CCH in the gas phase

“…We address this challenge by employing a divide and conquer approach. In this approach the calculation of the sticking curve is split into three consecutive steps 29,30 . In a first step, the PES of the molecule-surface interaction is mapped as a function of the relevant coordinates.…”

Dynamical steering in an electron transfer surface reaction: Oriented NO(v = 3, 0.08 < Ei < 0.89 eV) relaxation in collisions with a Au(111) surface

“…Thus, the dissociation probability increases when H 2 incidence energy of translation is reduced from 0.25 eV to 0.02 eV. 11 Six-dimensional quantum dynamical computations using a density functional theory (DFT) derived potential energy surface, 12,13 which reproduce a number of experimental observations, show H 2 can be re-orientated to a favorable reaction geometry at low incidence energy because the interaction time is large. At higher incidence translational energy, where the time for re-orientation is reduced, the reaction probability is also reduced.…”

Diffractive and reactive scattering of (v=0, j=0) HD from Pt(111): Six-dimensional quantum dynamics compared with experiment

“…[17][18][19][20][21][22][23][24][25][26][27][28] Much attention has been devoted to HD scattering from Pt͑111͒ because of, inter alia, the high probabilities for rotational excitation to only a limited number of accessible rotational states. Experimental efforts by Cowin and co-workers 1,2 have been followed by several theoretical studies of this system, employing either Wigner R-matrix theory 27,29 or EngdahlMoiseyev-Maniv T-matrix methods 28 to obtain rotationally inelastic scattering probabilities.…”