Ab initio molecular dynamics simulations of molecular scattering from metal(111) surfaces

by Jan Altschäffel
Doctoral thesis
Date of Examination:2021-05-27
Date of issue:2021-08-26
Advisor:Prof. Dr. Alec M. Wodtke
Referee:Prof. Dr. Alec M. Wodtke
Referee:Prof. Dr. Dirk Schwarzer
Persistent Address: http://dx.doi.org/10.53846/goediss-8797

 

 

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Abstract

English

In this thesis, I report on ab initio molecular dynamics (AIMD) simulations of scattering experiments of CO and NO from Au(111) and Ag(111) surfaces and provide minimum energy pathway (MEP) calculations of the dissociation reactions of hydrogen halides and NO on different metal(111) surfaces. Furthermore, I did calculations of the transition dipole moment to investigate the electronic interaction of CO on different surfaces and calculated the electronic ground state energy for CO at different surfaces and NO/Au(111). Finally, I computed the phonon spectra of (Ag-covered) Au(111) and Ag(111) surfaces to look into their mechanical properties, because they can influence the scattering behavior. A comparison between experimental results and the adiabatic simulations for CO in low vibrational states shows a nearly quantitative agreement, and thus non-adiabatic effects, like electron-hole pair (ehp) excitation, can be neglected. The disagreement between the adiabatic simulations and the experiment suggests a more dominant role of non-adiabatic effects in the scattering dynamics of highly vibrationally excited NO and CO from metal surfaces. The computed phonon spectra for Au(111), Ag(111) and Ag-covered Au(111) surfaces suggest a purely mechanical energy transfer for the translational energy of CO(v=2) to the surface phonons which is in agreement with the results of the computed AIMD simulations. The transition state (TS) configurations for all dissociation reactions show an elongated molecular internuclear distance, and therefore we can assume that the dissociation reactions are promoted via vibrational excitation according to Polanyi’s rules. The obtained density functional theory (DFT) data for NO/Au(111) can be fitted to obtain a diabatic potential with a neutral and an anionic state, where NO$^{-}$ is formed to enable molecular dynamics (MD) simulations in the framework of the independent electron surface hopping (IESH) approach.
Keywords: Phonon spectra; transition dipole moment; simulation of scattering experiments; Ab initio molecular dynamics; metal surfaces; non-adiabatic effects; diatomic molecule surface interaction; Density functional theory; minimum energy pathways; energy conversion; Born-Oppenheimer breakdown
 
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