Phonon and electron excitations in abstraction processes from metallic surfaces

132 p.Tesi honetan W(100) eta W(110) gainazaletan gertatzen diren H(g)+H(ads) eta N(g)+N(ads) errekonbinazio erreakzioak ikertu dira. Helburu nagusia erreakzio hauetan gertatzen diren kitzikapen elektronikoak aztertzea izan da. Hortarako, erreakzioa pausuz pausu jarraitzeko gaitasuna ematen digun dinamika kuasiklasiko deritzon metodo teorikoa erabili da. DFT bidez kalkulaturiko energia potentzial gainazaletan oinarritu dira simulazioak. LDFA eta GLO modeloak erabili dira erreakzioak metalean eragiten dituen kitzikapen elektroniko eta fononikoak ikertzeko, hurrenez hurren. Tenperaturak altuak ez direnean, errekonbinazioa Eley-Rideal (ER) edo Hot-atom (HA) deritzen mekanismoen bidez gerta liteke. Lehenengo kasuan, gas faseko (g) eta gainazaleko (ads) atomoek bat batean erreakzionatzen dute. HA mekanismoan, aldiz, gas faseko atomoa gainazalean mugitzen da denbora tarte batez erreakzionatu aurretik. Aurrekariekin bat, kitzikapen elektronikoen kontribuzioa energia galera totalari handiagoa da atomoen masa txikiagoa denenan. Kitzikapen elektronikoek, espero bezela, HA mekanismoan dute eragin gehien. Gaineztatze baxuetan gas faseko atomoen energia zinetikoa baxua denean, kitzikapen elektronikoak direla eta HA erreakzioa asko murrizten da. ER erreatibitatean eragin baxuagoa du aldiz. Dena den energia galerak esanguratsuak direla aurkitzen da mekanismo bietan. Horotara, tesi honetan errekonbinazio erreakzioen deskribapen teorikoan aurrera egin da kitzikapen elektronikoak kontutan izanez

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]

Kinetics of NH3 Desorption and Diffusion on Pt: Implications for the Ostwald Process.

We report accurate time-resolved measurements of NH3 desorption from Pt(111) and Pt(332) and use these results to determine elementary rate constants for desorption from steps, from (111) terrace sites and for diffusion on (111) terraces. Modeling the extracted rate constants with transition state theory, we find that conventional models for partition functions, which rely on uncoupled degrees of freedom (DOFs), are not able to reproduce the experimental observations. The results can be reproduced using a more sophisticated partition function, which couples DOFs that are most sensitive to NH3 translation parallel to the surface; this approach yields accurate values for the NH3 binding energy to Pt(111) (1.13 ± 0.02 eV) and the diffusion barrier (0.71 ± 0.04 eV). In addition, we determine NH3's binding energy preference for steps over terraces on Pt (0.23 ± 0.03 eV). The ratio of the diffusion barrier to desorption energy is 0.65, in violation of the so-called 12% rule. Using our derived diffusion/desorption rates, we explain why established rate models of the Ostwald process incorrectly predict low selectivity and yields of NO under typical reactor operating conditions. Our results suggest that mean-field kinetics models have limited applicability for modeling the Ostwald process.D.B. and M.S. thank the BENCh graduate school, funded by the DFG (389479699/GRK2455). I.R. gratefully acknowledges the support by Israel Science Foundation, ISF (Grant No. 2187/19), and by the Open University of Israel Research Authority (Grant No. 31044). O.G. acknowledges financial support by the Spanish Ministerio de Ciencia e Innovación (Grant No. PID2019-107396GB-I00/AEI/10.13039/501100011033). T.N.K., G.S., M.S., and J.F. acknowledge support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 833404)

Phonon and electron excitations in abstraction processes from metallic surfaces

132 p.Tesi honetan W(100) eta W(110) gainazaletan gertatzen diren H(g)+H(ads) eta N(g)+N(ads) errekonbinazio erreakzioak ikertu dira. Helburu nagusia erreakzio hauetan gertatzen diren kitzikapen elektronikoak aztertzea izan da. Hortarako, erreakzioa pausuz pausu jarraitzeko gaitasuna ematen digun dinamika kuasiklasiko deritzon metodo teorikoa erabili da. DFT bidez kalkulaturiko energia potentzial gainazaletan oinarritu dira simulazioak. LDFA eta GLO modeloak erabili dira erreakzioak metalean eragiten dituen kitzikapen elektroniko eta fononikoak ikertzeko, hurrenez hurren. Tenperaturak altuak ez direnean, errekonbinazioa Eley-Rideal (ER) edo Hot-atom (HA) deritzen mekanismoen bidez gerta liteke. Lehenengo kasuan, gas faseko (g) eta gainazaleko (ads) atomoek bat batean erreakzionatzen dute. HA mekanismoan, aldiz, gas faseko atomoa gainazalean mugitzen da denbora tarte batez erreakzionatu aurretik. Aurrekariekin bat, kitzikapen elektronikoen kontribuzioa energia galera totalari handiagoa da atomoen masa txikiagoa denenan. Kitzikapen elektronikoek, espero bezela, HA mekanismoan dute eragin gehien. Gaineztatze baxuetan gas faseko atomoen energia zinetikoa baxua denean, kitzikapen elektronikoak direla eta HA erreakzioa asko murrizten da. ER erreatibitatean eragin baxuagoa du aldiz. Dena den energia galerak esanguratsuak direla aurkitzen da mekanismo bietan. Horotara, tesi honetan errekonbinazio erreakzioen deskribapen teorikoan aurrera egin da kitzikapen elektronikoak kontutan izanez

Phonon and electron excitations in diatom abstraction from metallic surfaces

La rationalisation des processus chimiques élémentaires aux surfacesest d'intérêt primordial pour de nombreux phénomènes naturels ou d'intérêttechnologique. D'un point de vue fondamental, la façon dont l'énergie, concomitanteà toute réaction chimique, est distribuée parmi les degrés de liberté des moléculesformées et/ou transférée à la surface est loin d'être systématisée. Dans ce travail,des simulations, reposant sur la méthode des trajectoires quasi-classiques (QCT),sont réalisées pour examiner cette problématique lors de recombinaisons demolécules d'hydrogène (H2) et d'azote (N2) résultant de l'abstraction d'atomesadsorbés via collision par un atome provenant de la phase gazeuse sur des surfacesde Tungstène - W(100) et W(110) - à taux de couverture non nul. Ces processussont ici étudiés pour leur intérêt en physique des interactions plasma-paroi. Dessurfaces d'énergie potentielle, construites à partir de calculs de structure électroniquebasés sur la théorie de la fonctionnelle densité (DFT), sont utilisées pour simuler,dans le cadre de la mécanique classique - incluant les corrections semi-classiquespertinentes - les processus ultrarapides dit de "Eley-Rideal" et par "atomes-chauds"(sub-picoseconde). La mise en place de modèle effectifs, pour tenir compte de ladissipation de l'énergie aux phonons de la surface et aux excitations électroniques(paires électron-trou), permet de rationaliser la dynamique non-adiabatique del'abstraction atomique aux surfaces métalliques.The rationalization of elementary processes at surfaces is of prime importance for numerous natural and technological areas. From a fundamental pointof view, the way the energy concomitant to any chemical reaction is distributed among the desorbing molecules degrees-of-freedom and the surface is far frombeing fully pictured. In this work, quasiclassical molecular dynamics (QCT)simulations have been carried out to investigate this issue for the recombination ofH2 and N2 resulting from atomic adsorbate abstraction by atom scattering off theW(100) and W(110) covered surfaces, these processes being of relevance inplasma-wall interactions. Potential energy surfaces, built from density functional(DFT) theory calculations, have been used to simulate, within the framework ofclassical dynamics (including semi-classical corrections), the subpicosecond Eley-Rideal and Hot-Atom processes. The implementation of effective models to accountfor energy dissipation to surface phonons and electron-hole pair excitations, have allowed to rationalize the non-adidabatic dynamics of atom abstraction at metalsurfaces

Excitations électroniques et phononiques au cours de réaction d'abstraction diatomiques de surfaces métalliques

The rationalization of elementary processes at surfaces is of prime importance for numerous natural and technological areas. From a fundamental pointof view, the way the energy concomitant to any chemical reaction is distributed among the desorbing molecules degrees-of-freedom and the surface is far frombeing fully pictured. In this work, quasiclassical molecular dynamics (QCT)simulations have been carried out to investigate this issue for the recombination ofH2 and N2 resulting from atomic adsorbate abstraction by atom scattering off theW(100) and W(110) covered surfaces, these processes being of relevance inplasma-wall interactions. Potential energy surfaces, built from density functional(DFT) theory calculations, have been used to simulate, within the framework ofclassical dynamics (including semi-classical corrections), the subpicosecond Eley-Rideal and Hot-Atom processes. The implementation of effective models to accountfor energy dissipation to surface phonons and electron-hole pair excitations, have allowed to rationalize the non-adidabatic dynamics of atom abstraction at metalsurfaces.La rationalisation des processus chimiques élémentaires aux surfacesest d'intérêt primordial pour de nombreux phénomènes naturels ou d'intérêttechnologique. D'un point de vue fondamental, la façon dont l'énergie, concomitanteà toute réaction chimique, est distribuée parmi les degrés de liberté des moléculesformées et/ou transférée à la surface est loin d'être systématisée. Dans ce travail,des simulations, reposant sur la méthode des trajectoires quasi-classiques (QCT),sont réalisées pour examiner cette problématique lors de recombinaisons demolécules d'hydrogène (H2) et d'azote (N2) résultant de l'abstraction d'atomesadsorbés via collision par un atome provenant de la phase gazeuse sur des surfacesde Tungstène - W(100) et W(110) - à taux de couverture non nul. Ces processussont ici étudiés pour leur intérêt en physique des interactions plasma-paroi. Dessurfaces d'énergie potentielle, construites à partir de calculs de structure électroniquebasés sur la théorie de la fonctionnelle densité (DFT), sont utilisées pour simuler,dans le cadre de la mécanique classique - incluant les corrections semi-classiquespertinentes - les processus ultrarapides dit de "Eley-Rideal" et par "atomes-chauds"(sub-picoseconde). La mise en place de modèle effectifs, pour tenir compte de ladissipation de l'énergie aux phonons de la surface et aux excitations électroniques(paires électron-trou), permet de rationaliser la dynamique non-adiabatique del'abstraction atomique aux surfaces métalliques