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A combined quantum chemical/molecular dynamics study of X-ray photoelectron spectra of polyvinyl alcohol using oligomer models

  • X-ray photoelectron spectroscopy (XPS) is a powerful tool for probing the local chemical environment of atoms near surfaces. When applied to soft matter, such as polymers, XPS spectra are frequently shifted and broadened due to thermal atom motion and by interchain interactions. We present a combined quantum mechanical QM/molecular dynamics (MD) simulation of X-ray photoelectron spectra of polyvinyl alcohol (PVA) using oligomer models in order to account for and quantify these effects on the XPS (C1s) signal. In our study, molecular dynamics at finite temperature were performed with a classical forcefield and by ab initio MD (AIMD) using the Car-Parrinello method. Snapshots along, the trajectories represent possible conformers and/or neighbouring environments, with different C1s ionization potentials for individual C atoms leading to broadened XPS peaks. The latter are determined by Delta-Kohn Sham calculations. We also examine the experimental practice of gauging XPS (C1s) signals of alkylic C-atoms in C-containing polymers to theX-ray photoelectron spectroscopy (XPS) is a powerful tool for probing the local chemical environment of atoms near surfaces. When applied to soft matter, such as polymers, XPS spectra are frequently shifted and broadened due to thermal atom motion and by interchain interactions. We present a combined quantum mechanical QM/molecular dynamics (MD) simulation of X-ray photoelectron spectra of polyvinyl alcohol (PVA) using oligomer models in order to account for and quantify these effects on the XPS (C1s) signal. In our study, molecular dynamics at finite temperature were performed with a classical forcefield and by ab initio MD (AIMD) using the Car-Parrinello method. Snapshots along, the trajectories represent possible conformers and/or neighbouring environments, with different C1s ionization potentials for individual C atoms leading to broadened XPS peaks. The latter are determined by Delta-Kohn Sham calculations. We also examine the experimental practice of gauging XPS (C1s) signals of alkylic C-atoms in C-containing polymers to the C1s signal of polyethylene. We find that (i) the experimental XPS (C1s) spectra of PVA (position and width) can be roughly represented by single-strand models, (ii) interchain interactions lead to red-shifts of the XPS peaks by about 0.6 eV, and (iii) AIMD simulations match the findings from classical MD semi-quantitatively. Further, (iv) the gauging procedure of XPS (C1s) signals to the values of PE, introduces errors of about 0.5 eV. (C) 2014 Elsevier B.V. All rights reserved.show moreshow less

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Metadaten
Author:Christopher EhlertORCiDGND, Dominik Kröner, Peter SaalfrankORCiDGND
DOI:https://doi.org/10.1016/j.elspec.2014.12.007
ISSN:0368-2048 (print)
ISSN:1873-2526 (online)
Parent Title (English):Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy
Publisher:Elsevier
Place of publication:Amsterdam
Document Type:Article
Language:English
Year of first Publication:2015
Year of Completion:2015
Release Date:2017/03/27
Tag:Classical MD; Delta-Kohn Sham method; Interchain interactions; Poly vinyl alcohol; Simulation of polymer XPS; Thermal broadening effects
Volume:199
Pagenumber:8
First Page:38
Last Page:45
Funder:BAM (BAM MIS programme) [Ideen_2012_59]
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Chemie
Peer Review:Referiert