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We have studied the dissociative chemisorption and scattering of N2 on and from Ru(0001), using a six-dimensional quasiclassical trajectory method. The potential energy surface, which depends on all the molecular degrees of freedom, has been built applying a modified Shepard interpolation method to a data set of results from density functional theory, employing the RPBE generalized gradient approximation. The frozen surface and Born-Oppenheimer [Ann. Phys. (Leipzig) 84, 457 (1927)] approximations were used, neglecting phonons and electron-hole pair excitations. Dissociative chemisorption probabilities are found to be very small even for translational energies much higher than the minimum reaction barrier, in good agreement with experiment. A comparison to previous low dimensional calculations shows the importance of taking into account the multidimensional effects of N2 rotation and translation parallel to the surface. The new calculations strongly suggest a much smaller role of nonadiabatic effects than previously assumed on the basis of a comparison between low dimensional results and experiments [J. Chem. Phys. 115, 9028 (2001)]. Also in agreement with experiment, our theoretical results show a strong dependence of reaction on the initial vibrational state. Computed angular scattering distributions and parallel translation energy distributions are in good agreement with experiments on scattering, but the theory overestimates vibrational and rotational excitations in scattering. [ABSTRACT FROM AUTHOR]

Six-dimensional quantum dynamical calculations are reported for the dissociative chemisorption of (v=0, 1, j=0) H2 on Cu(100), and for rovibrationally inelastic scattering of (v=1, j=1) H2 from Cu(100). The dynamics results were obtained using a new potential-energy surface (PES5), which was based on density-functional calculations using a slab representation of the adsorbate-substrate system and a generalized gradient approximation to the exchange-correlation energy. A very accurate method (the corrugation reducing procedure) was used to represent the density-functional theory data in a global potential-energy surface. With the new, more accurately fitted PES5, the agreement between the dynamics results and experimental results for reaction and rovibrationally elastic scattering is not as good as was obtained with a previous potential-energy surface (PES4), which was based on a subset of the density-functional theory data not yet including the results for the low-symmetry Cu sites. Preliminary density-functional theory results suggest that the agreement between theory and experiment will improve over that obtained with PES5 if the density-functional calculations are repeated using a larger basis set and using more copper layers than employed in PES4 and PES5. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have used a modified Shepard (MS) interpolation method, initially developed for gas phase reactions, to build a potential energy surface (PES) for studying the dissociative chemisorption of H[sub 2] on Pt(111). The aim was to study the efficiency and the accuracy of this interpolation method for an activated multidimensional molecule–surface reactive problem. The strategy used is based on previous applications of the MS method to gas phase reactions, but modified to take into account special features of molecule–surface reactions, like the presence of many similar reaction pathways which vary only slightly with surface site. The efficiency of the interpolation method was tested by using an already existing PES to provide the input data required for the construction of the new PES. The construction of the new PES required half as many ab initio data points as the construction of the old PES, and the comparison of the two PESs shows that the method is able to reproduce with good accuracy the most important features of the H[sub 2]+Pt(111) interaction potential. Finally, accuracy tests were done by comparing the results of dynamics simulations using the two different PESs. The good agreement obtained for reaction probabilities and probabilities for rotationally and diffractionally inelastic scattering shows clearly that the MS interpolation method can be used efficiently to yield accurate PESs for activated molecule–surface reactions. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Following earlier three-dimensional (3D) calculations, we present results of four-dimensional (4D) calculations on dissociative and diffractive scattering of H[sub 2] from Pt(111) by extending the 3D model with a second degree of freedom parallel to the surface. A 4D potential energy surface (PES) is constructed by interpolating four 2D PESs obtained from density-functional theory calculations using the generalized gradient approximation and a slab representation of the metal surface. The 4D calculations show that out-of-plane diffraction is much more efficient than in-plane diffraction, providing a partial explanation for the paradox that diffraction experiments measure little in-plane diffraction, whereas experiments on reaction suggest the surface to be corrugated. Calculations for off-normal incidence of υ=0 H[sub 2] show that, in agreement with experiment, initial parallel momentum inhibits dissociation at low normal translational energies, and enhances reaction for higher energies. Our 4D calculations also show that the reaction of initial υ = 1 H[sub 2] is vibrationally enhanced with respect to υ = 0 H[sub 2], as was found in the 3D model, even though H[sub 2]+Pt(111) is an early barrier system. [ABSTRACT FROM AUTHOR]

The H2+LiF(001) system was used to investigate the performance of the hybrid close-coupling wave packet (CCWP) method and of a symmetry adapted, fully close-coupled wave packet (SAWP) method for a molecule–surface problem characterized by fairly high corrugation. In the calculations, a realistic, [lowercase_phi_synonym]-dependent model potential was used. The calculations were performed for a collision energy of 0.2 eV, with H2 initially in its j=0 rotational state at normal incidence to the surface. Large increases in the computational efficiencies of both wave packet methods were achieved by taking advantage of the potential coupling matrices associated with both methods becoming sparser with increasing molecule–surface distance. For the present model problem and employing this increased sparseness at longer range, the SAWP method is faster than the CCWP method by a factor of 2. The potential usefulness of the SAWP method for dissociative chemisorption problems is discussed. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have investigated the performance of a fully close-coupled wave packet method and its symmetry-adapted version for a model problem of H2 scattering from LiF(001). The computational cost of the fully close-coupled methods scales linearly with the number of rotation-diffraction states present in the basis set, provided that the sparseness of the potential coupling matrix is taken into account. For normal incidence, the symmetry adapted version is faster than the conventional close-coupling wave packet method by almost an order of magnitude. An extension of the method to more realistic molecule-surface problems is considered. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The close-coupling wave packet (CCWP) method has been adapted for performing calculations on molecule-surface scattering with arbitrary angles of incidence. The method used involves a slight modification of the fast Fourier transform (FFT) technique for evaluating the action of the translational kinetic energy operator on the wave function, employing the shifting theorem of Fourier analysis. We present and compare results of CCWP and close-coupling (CC) calculations on the He+LiF and H2+LiF systems using simple model potentials. The results presented establish the validity of the proposed technique and may be useful as benchmarks. [ABSTRACT FROM AUTHOR]

Results of quantum calculations on rotationally and vibrationally inelastic scattering of 1Au(S1) trans-glyoxal by H2,He, and Ar(E=80 meV) are presented. For scattering of 00 glyoxal and 72 glyoxal by H2, a quantitative comparison with a recent crossed beam experiment is made. The calculated cross sections for rotationally inelastic scattering are in good agreement with the experimental values, and the trend that σ(72, k=0→72, k’) falls off faster with k’ than σ(00, k=0→00, k’) is reproduced. Our calculations do not reproduce the experimental finding that, for the initial 72 level, the cross sections for the Δv7=-1 and Δv7=+1 transitions are nearly identical. The calculations on 72 glyoxal + He and Ar show important differences with 72 glyoxal + H2 in the competition of rotational excitation with vibrational excitation. Model calculations also presented here yield some interesting trends in the k’ dependence of the cross sections σ(00, k=0→x1, k’) on the vibrational mode x excited. [ABSTRACT FROM AUTHOR]

Using the Monte Carlo classical trajectory (CT) method and the azimuthal close-coupled, infinite-order sudden (ACC-IOS) method, we have calculated cross sections for rotational excitation of S1 trans-glyoxal by H2 at E=80 meV. The cross sections σ(k=0, j→k’) calculated with the CT method are nearly independent of j. The classical values of σ(k=0, j=5→k’) are in good agreement with the quantum values of σ(k=0→k’) for 2≤k’≤12, although the quantum calculations show a slight preference for odd Δk transitions which is not found in the CT calculations. Both the CT results and the ACC-IOS results are in good agreement with results obtained in a recent crossed beam experiment. Rotational excitation to high k’ (k’=11,12) occurs by collisions of H2 with one of the H atoms of glyoxal, and the initial value of the orbital angular momentum approximately equals the final value of k in such collisions. Since backward scattering is dominant in collisions leading to high k’, angular momentum constraints alone cannot explain the maximum observed in Δk experimentally (Δk=14). [ABSTRACT FROM AUTHOR]

We present new experimental and theoretical results for reactive scattering of dihydrogen from Cu(100). In the new experiments, the associative desorption of H2 is studied in a velocity resolved and final rovibrational state selected manner, using time-of-flight techniques in combination with resonance-enhanced multi-photon ionization laser detection. Average desorption energies and rotational quadrupole alignment parameters were obtained in this way for a number of (v = 0, 1) rotational states, v being the vibrational quantum number. Results of quantum dynamics calculations based on a potential energy surface computed with a specific reaction parameter (SRP) density functional, which was derived earlier for dihydrogen interacting with Cu(111), are compared with the results of the new experiments and with the results of previous molecular beam experiments on sticking of H2 and on rovibrationally elastic and inelastic scattering of H2 and D2 from Cu(100). The calculations use the Born-Oppenheimer and static surface approximations. With the functional derived semi-empirically for dihydrogen + Cu(111), a chemically accurate description is obtained of the molecular beam experiments on sticking of H2 on Cu(100), and a highly accurate description is obtained of rovibrationally elastic and inelastic scattering of D2 from Cu(100) and of the orientational dependence of the reaction of (v = 1, j = 2 - 4) H2 on Cu(100). This suggests that a SRP density functional derived for H2 interacting with a specific low index face of a metal will yield accurate results for H2 reactively scattering from another low index face of the same metal, and that it may also yield accurate results for H2 interacting with a defected (e.g., stepped) surface of that same metal, in a system of catalytic interest. However, the description that was obtained of the average desorption energies, of rovibrationally elastic and inelastic scattering of H2 from Cu(100), and of the orientational dependence of reaction of (v = 0, j = 3 - 5, 8) H2 on Cu(100) compares less well with the available experiments. More research is needed to establish whether more accurate SRP-density functional theory dynamics results can be obtained for these observables if surface atom motion is added to the dynamical model. The experimentally and theoretically found dependence of the rotational quadrupole alignment parameter on the rotational quantum number provides evidence for rotational enhancement of reaction at low translational energies. [ABSTRACT FROM AUTHOR]

A comparison between experiment and theory is performed for the scattering of (v=1, j=1) H[sub 2] from Cu(100) at normal incidence. Experimentally, this system was studied using molecular beam techniques, with stimulated Raman pumping employed to overpopulate (v=1, j=1) in the incident beam, and resonance enhanced multi-photon ionization used to detect the H[sub 2] scattered in two (v=1, j) states, and two (v=0, j) states. Theoretically, six-dimensional wave packet calculations were performed, employing a new, extended potential energy surface that was computed with density functional theory, using the generalized gradient approximation and a slab representation of the metal surface. Theory and experiment are in good agreement for the survival probability, i.e., the probability for rovibrationally elastic scattering. However, the theory overestimates the probabilities for rotationally inelastic scattering (to v=1, j=3) and for rovibrationally inelastic scattering (to v=0, j=5 and 7) for channels that could be determined experimentally. The cause of these discrepancies is discussed, as are possibilities for future improvements in the theory as well as the experiment. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]