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We study the dissociative dynamics of O2 molecules on the Ag(100) surface. Initially, the impinging molecules are either in the spin-triplet ground state or in the spin-singlet excited state. The molecule-surface interaction is obtained in each case by constructing the six-dimensional potential energy surface (PES) from the interpolation of the energies calculated with spin-polarized and non-spin-polarized density functional theories, respectively. Classical trajectory calculations performed in both PESs show that O2 molecules initially in the spin-triplet ground state only dissociate for incidence energies above 1.05 eV. This result is consistent with molecular beam experiments performed in this system. Interestingly, our results also suggest that for the spin-singlet O2 dissociation occurs even for incidence energies as low as 50 meV. We propose the use of spin-singlet excited O2 molecules to improve the otherwise low dissociative reactivity of O2 at clean Ag(100). [ABSTRACT FROM AUTHOR]

We study the relaxation of hot H atoms produced by dissociation of H2 molecules on the Pd(111) surface. Ab initio density-functional theory calculations and the “corrugation reducing procedure” are used to determine the interaction potential for a H atom in front of a rigid surface as well as its modification under surface-atom vibrations. A slab of 80 Pd atoms is used to model the surface together with “generalized Langevin oscillators” to account for energy dissipation to the bulk. We show that the energy relaxation is fast, about 75% of the available energy being lost by the hot atoms after 0.5 ps. As a consequence, the hot atoms do not travel more than a few angstroms along the surface before being trapped into the potential well located over the hollow site. [ABSTRACT FROM AUTHOR]

By applying a corrugation-reducing procedure we have interpolated the six-dimensional (6D) potential energy surfaces for the H[sub 2]/Pt(111) and H[sub 2]/Cu(100) systems from data obtained by density functional theory (DFT) calculations. We have compared interpolated values with a large number of DFT results not used in the basis for the interpolation and we have obtained an average error below 20 meV and a maximum error of about 30 meV in the regions important for dissociative adsorption. Near the surface the corrugation-reducing procedure gives excellent results using only data from high-symmetry sites. However, we show that to reach the above mentioned accuracy level far from the surface, it is necessary to include information from at least one low-symmetry site. Care has been taken to demonstrate the quality of the interpolation along all degrees of freedom in different regions of the configuration space. The strengths of the method are shown together with the aspects requiring careful handling. A comparison with a direct interpolation method is also made. [ABSTRACT FROM AUTHOR]

An efficient method is proposed to construct the six-dimensional Potential Energy Surface (PES) for diatomic molecule-surface interactions from low dimensional cuts obtained in ab initio calculations. The efficiency of our method results from a corrugation-reducing procedure based on the observation that most of the corrugation in a molecule-surface PES is already embedded in the atom-surface interactions. Hence, substraction of the latter leads to a much smoother function which makes accurate interpolations possible. The proposed method is a general one and can be implemented in a systematic way for any system. Its efficiency is illustrated for the case of H[sub 2]/Pd(111) by using recent ab initio data. We report also the results of very stringent checks against ab initio calculations not used in the interpolation. These checks show the high accuracy of our method. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]