Ab Initio Molecular Dynamics of Hydrogen on Tungsten Surfaces

The dissociation process of hydrogen molecules on W(110) was studied using density functional theory and classical molecular dynamics. We have calculated the dissociation probability for molecules with energies below 300 meV and analyzed the dynamics of the adsorption process. Our results show that the fate of each trajectory is determined at distances relatively far from the surface, at roughly 2-2.5 angstrom. This distance varies slightly with the initial kinetic energy of the molecule. Part of our simulations include van der Waals dispersion effects in the interaction between molecule and surface. We present a comparison between these results and other theoretical and experimental results previously published. The inclusion of the van der Waals term provokes an increase in the far-distance attraction that is compensated by a stronger repulsion at short distances. The combination of both effects appreciably decreases the value of the dissociation probability. The successful comparison of our results with experimental information confirms that the methodology employed can be considered as a rich and accurate instrument to study the dissociation of hydrogen on surfaces.A. R. F. acknowledges financial support by the University of Bordeaux. This work was conducted in the scope of the transborder joint Laboratory “QuantumChemPhys: Theoretical Chemistry and Physics at the Quantum Scale” (ANR-10-IDEX-03-02). This work has been supported in part by the Basque Departamento de Educación, Universidades e Investigación, the University of the Basque Country UPV/EHU (Grant No. IT1246-19) and the Spanish Ministerio de Ciencia e Innovación (PID2019-107396GB-I00/AEI/10.13039/501100011033)

Erratum: >A comparative study of the Si+O2\SiO+O reaction dynamics from quasiclassical trajectory and statistical based methods> [J. Chem. Phys. 128, 174307 (2008)]

Peer Reviewe

H atom scattering from W(110): A benchmark for molecular dynamics with electronic friction.

Molecular dynamics with electronic friction (MDEF) at the level of the local density friction approximation (LDFA) has been applied to describe electronically non-adiabatic energy transfer accompanying H atom collisions with many solid metal surfaces. When implemented with full dimensional potential energy and electron density functions, excellent agreement with experiment is found. Here, we compare the performance of a reduced dimensional MDEF approach involving a simplified description of H atom coupling to phonons to that of full dimensional MDEF calculations known to yield accurate results. Both approaches give remarkably similar results for H atom energy loss distributions with a 300 K W(110) surface. At low surface temperature differences are seen; but, quantities like average energy loss are still accurately reproduced. Both models predict similar conditions under which H atoms that have penetrated into the subsurface regions could be observed in scattering experiments.The authors acknowledge the support of the French Embassy in Cuba, the University of Bordeaux, the CNRS, the Erasmus Mundus programme for funding and ISM and University of Bordeaux for providing computing resources. This work was conducted in the scope of the transborder joint Laboratory QuantumChemPhys: Theoretical Chemistry and Physics at the Quantum Scale (ANR-10-IDEX-03-02). This work was partly performed in the framework of the Elementary Dynamical Processes at Model Catalytic Surfaces (EDPMCS) Experiment, a part of the Molecular Physics at Interfaces Initiative at the Dalian Coherent Light Source. NH, AK and AMW acknowledge support for this project from the Max Planck Society Central Funds, the international partnership program of the Chinese Academy of Science (No. 121421KYSB20170012) as well as the Max Planck Institute for Multidisciplinary Sciences and the Georg-August University of Goettingen. We further acknowledge support from the Deutsche Forschungsgemeinschaft under Grant number 217133147, which is part of the Collaborative research Center 1073 operating Project A04. AK acknowledges European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement no. 833404). OG acknowledges financial support by the Spanish Ministerio de Ciencia e Innovacion [Grant No. PID2019-107396GB-I00/AEI/10.13039/501100011033]

Classical dynamics study of atomic oxygen over graphite (0001) with new interpolated and analytical potential energy surfaces

Two adiabatic potential energy surfaces (PESs) based on density functional theory data are constructed for the interaction of atomic oxygen with graphite (0 0 0 1) surface: an analytical FPLEPS PES and an interpolated Modified Shepard one. A classical trajectory study has been performed for the two PESs for different initial conditions: collision energy (0.1 ⩽ Ecol ⩽ 1.3 eV), surface temperature (100 ⩽ Tsurf ⩽ 900 K) and two incident angles (θv = 0°, 45°), and also for thermal conditions (T = TOxygen = Tsurf = 300-1500 K). In addition, hyperthermal experimental conditions corresponding to a hot atom distribution (〈Ecol〉 = 5.2 eV) were also considered. All the properties studied for the two PESs were in close agreement in almost the major part of the explored conditions, although some differences were obtained for low Ecol due to the presence of a physisorption minimum in the MS PES that was not included into the FPLEPS one. The adsorption process occurs mainly over bridge sites. Adsorption probabilities are lower than reflection ones in practically all the conditions explored and increase quickly with Ecol until a maximum and then decrease smoothly. Polar scattering angle distributions present a peak centred around the specular angle position and broaden when increasing Ecol or Tsurf. A good agreement respect this peak position was found in comparison with the experimental hyperthermal data. The transfer of energy is mainly from the atom to the surface and increases when initial collision energy does

Energy dissipation to tungsten surfaces upon hot-atom and Eley-Rideal recombination of H 2

Adiabatic and nonadiabatic quasi-classical molecular dynamics simulations are performed to investigate the role of electron-hole pair excitations in hot-atom and Eley-Rideal H 2 recombination mechanisms on H-covered W(100). The influence of the surface structure is analyzed by comparing with previous results for W(110). In the two surfaces, hot-atom abstraction cross sections are drastically reduced due to the efficient energy exchange with electronic excitations at low incident energies and low coverage, while the effect on Eley-Rideal reactivity is negligible. As the coverage increases, the projectile energy is more efficiently dissipated into the other adsorbates. Consequently, the effect of electronic excitations is reduced. As a result, the reactivity and final energy distributions of the formed H 2 molecules are similar for both abstraction mechanisms.Fil: Galparsoro, Oihana. Centre National de la Recherche Scientifique; Francia. Universite de Bordeaux; FranciaFil: Busnengo, Heriberto Fabio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Martinez, Alejandra Elisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Juaristi, Joseba Iñaki. Donostia International Physics Center; España. Universidad del País Vasco; España. Consejo Superior de Investigaciones Científicas; EspañaFil: Alducin, Maite. Donostia International Physics Center; España. Universidad del País Vasco; España. Consejo Superior de Investigaciones Científicas; EspañaFil: Larregaray, Pascal. Centre National de la Recherche Scientifique; Francia. Universite de Bordeaux; Franci

Recombination and chemical energy accommodation coefficients from chemical dynamics simulations: O/O2 mixtures reacting over a β-cristobalite (001) surface

A microkinetic model is developed to study the reactivity of an O/O2 gas mixture over a -cristobalite (001) surface. The thermal rate constants for the relevant elementary processes are either inferred from quasiclassical trajectory calculations or using some statistical approaches, resting on a recently developed interpolated multidimensional potential energy surface based on density functional theory. The kinetic model predicts a large molecular coverage at temperatures lower than 1000 K, in contrary to a large atomic coverage at higher temperatures. The computed atomic oxygen recombination coefficient, mainly involving atomic adsorption and Eley-Rideal recombination, is small and increases with temperature in the 700-1700 K range (0.01 < gamma_O < 0.02) in good agreement with experiments. In the same temperature range, the estimated chemical energy accommodation coefficient, the main contribution to which is the atomic adsorption process is almost constant and differs from unity (0.75 < beta_O < 0.80)

Study of the H+O2 reaction by means of quantum mechanical and statistical approaches: The dynamics on two different potential energy surfaces

The possible existence of a complex-forming pathway for the H+O2 reaction has been investigated by means of both quantum mechanical and statistical techniques. Reaction probabilities, integral cross sections, and differential cross sections have been obtained with a statistical quantum method and the mean potential phase space theory. The statistical predictions are compared to exact results calculated by means of time dependent wave packet methods and a previously reported time independent exact quantum mechanical approach using the double many-body expansion (DMBE IV) potential energy surface (PES) [Pastrana et al., J. Phys. Chem. 94, 8073 (1990)] and the recently developed surface (denoted XXZLG) by Xu et al. [J. Chem. Phys. 122, 244305 (2005)]. The statistical approaches are found to reproduce only some of the exact total reaction probabilities for low total angular momenta obtained with the DMBE IV PES and some of the cross sections calculated at energy values close to the reaction threshold for the XXZLG surface. Serious discrepancies with the exact integral cross sections at higher energy put into question the possible statistical nature of the title reaction. However, at a collision energy of 1.6 eV, statistical rotationally resolved cross sections managed to reproduce the experimental cross sections for the H+O2(v=0,j=1)-->OH(v[prime]=1,j[prime])+O process reasonably well. ©2008 American Institute of Physic

Dynamical reaction pathways in Eley-Rideal recombination of nitrogen from W(100)

The scattering of atomic nitrogen over a N-pre-adsorbed W(100) surface is theoretically described in the case of normal incidence off a single adsorbate. Dynamical reaction mechanisms, in particular Eley-Rideal (ER) abstraction, are scrutinized in the 0.1-3.0 eV collision energy range and the influence of temperature on reactivity is considered between 300 and 1500 K. Dynamics simulations suggest that, though non-activated reaction pathways exist, the abstraction process exhibits a significant collision energy threshold (0.5 eV). Such a feature, which has not been reported so far in the literature, is the consequence of a repulsive interaction between the impinging and the pre-adsorbed nitrogens along with a strong attraction towards the tungsten atoms. Above threshold, the cross section for ER reaction is found one order of magnitude lower than the one for hot-atoms formation. The abstraction process involves the collision of the impinging atom with the surface prior to reaction but temperature effects, when modeled via a generalized Langevin oscillator model, do not affect significantly reactivity. © 2012 American Institute of Physics.E.Q.S. acknowledges the Bordeaux1-InSTEC inter university agreement and the French embassy in Cuba for fundings.Peer Reviewe