Ab initio-Molekulardynamik-Beschreibung von Adsorptionsprozessen komplexer Moleküle
Theoretische Chemie: Elektronenstruktur, Dynamik, Simulation
Zusammenfassung der Projektergebnisse
In summary, we employed first-principles based dynamical simulations to investigate industrially relevant surface reactions involving complex adsorbates beyond simple atoms or light diatomics such as molecular hydrogen. Considering the sizable amount of energy that may be released during such processes, particular focus was put on a quantitative account of the dissipative dynamics both during tlie early stages of adsorption and the ensuing thermalization process. We addressed for example the influence of pre-adsorbed water molecules on initial reactivity and on the kinetics governing the formation of hydrogen-bonded networks at the Pt(lll) surface. As the project moved on to more strongly chemisorbing adsorbates, we applied and tested various approaches to realistically model the energy sink provided by the substrate which we compared in terms of both accuracy and computational efficiency. As the question of energy dissipation directly interfaces with the efficiency of converting chemical energy, the present research interests extend thus increasingly into sustainability at the larger scale. Ultimately going beyond present limitations imposed by small simulation cells or assumptions commonly implied by system-bath coupling Hamiltonians, the novel QM/Me scheme offered novel qualitative insights into the microscopic details of phononic dissipation. Our results showed a strong dependence on the underlying surface symmetry, while suggesting that hyperthermal surface diffusion might be more common than hitherto anticipated. This prediction has ground-shaking consequences for microkinetic models of surface catalysis where the elementary reaction steps of adsorption and diffusion are treated as two decoupled, statistically unrelated elementary processes. The underlying Markovian state-to-state hopping, which was questioned here from a first-principles perspective, may thereby easily introduce an error of several orders of magnitude in the calculation of diffusion rates. Should reactions with other adsorbates in the vicinity of the original impingement point also be stimulated this way, further paradigm shifts would also be required to acconunodate such “hot” chemistry, for example, in our current understanding of heterogeneous catalysis. QM/Me will enable to address these aspects in systematic future studies, and also scrutinize the potential role of “hot” adatoms in other import dynamical processes such as the self-assembly of surface nanostructures, the first steps of oxide nuclcation and epitaxial growth, or adsorbateinduced surface reconstructions. Allowing now also for finally reaching a detailed atomistic understanding with respect to the influence of surface temperature, corresponding QM/Me studies will establish important trends for yet more complex systems aid elucidate experimentally proposed microscopic mechanisms. On a broader scope, the QM/Me methodology is generally suitable for application to any problem that breaks the translational symmetry of a metal in any number of periodic directions. Beyond the demonstrated relevance within a surface science context therefore, its applicability may be similarly extended to the bulk material for e.g. following interstitial diffusion, or addressing the chemistry around bulk defects and dislocations. We particularly envision QM/Me to play a prominent role in the investigation of radiation damage phenomena, where the ab initio treatment of nanoscale defects needs to be complemented with a realistic description of long-range elastic effects in large-scale atomistic simulations. Results obtained within the present project have been presented at numerous national and international conferences, including the 65th Lindau Nobel Laureate Meeting. Computationally demanding simulations at the TU Munich were performed based on generous CPU time provided from the Leibniz Rechenzentrum der Bayerischen Akademie der Wissenschaften.
Projektbezogene Publikationen (Auswahl)
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"Ready, Set and no Action: A Static Perspective on Potential Energy Surfaces commonly used in Gas-Surface Dynamics", Z. Phys. Chem. 227, 1523 (2013)
V. J. Bukas, J. Meyer, M. Alducin, and K. Reuter
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"Water Structures at Metal Electrodes Studied by Ab Initio Molecular Dynamics Simulation”, J. Electrochem. Soc. 161, E3015-E3020 (2014)
A. Groß, F. Gossenberger, X. Lin, M. Naderian, S. Sakong, and T. Roman
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“Modeling Heat Dissipation at the Nanoscale: An Embedding Approach for Chemical Reaction Dynamics on Metal Surfaces”, Angew. Chem. Int. Ed. 53, 4721-4724 (2014)
J. Meyer and K. Reuter
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“Role of Physisorption States in Molecular Scattering: A Semilocal Density-Functional Theory Study on O2/Ag(111)" Phys. Rev. Lett. 112, 156101 (2014)
I. Goikoctxca, J. Meyer, J. I. Juaristi, M. Alducin and K. Renter
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“Fingerprints of energy dissipation for exothermic surface chemical reactions: O2 on Pd(100)", J. Chem. Phys. 143, 034705 (2015)
V. J. Biikas, S. Mitra, J. Meyer, and K. Reuter
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Ab initio molecular dynamics simulations of the O2/Pt(111) interaction, Catal. Today 260, 60-65 (2016)
A. Groß
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“From single molecules to water networks: Dynamics of water adsorption on Pt(111)", J. Chem. Phys. 145, 094703 (2016)
M. Naderian and A. Groß
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“Hot Adatom Diffusion Follovhng Oxygen Dissociation on Pd(100) and Pd(111): A First-Principles Study of the Equilibration Dynamics of Exothermic Surface Reactions'", Phys. Rev. Lett. 117, 146101 (2016)
V. J. Bukas and K. Reuter
