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Author Gavrielides, A. ♦ Duguet, T. ♦ Esvan, J. ♦ Lacaze-Dufaure, C. ♦ Bagus, P. S.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY ♦ BINDING ENERGY ♦ EXPERIMENTAL DATA ♦ EXPLORATION ♦ HARTREE-FOCK METHOD ♦ POLYMERIZATION ♦ POLYMERS ♦ SIMULATION ♦ SPECTRA ♦ SURFACES ♦ X-RAY PHOTOELECTRON SPECTROSCOPY
Abstract Whereas poly-epoxy polymers represent a class of materials with a wide range of applications, the structural disorder makes them difficult to model. In the present work, we use good experimental model samples in the sense that they are pure, fully polymerized, flat and smooth, defect-free, and suitable for ultrahigh vacuum x-ray photoelectron spectroscopy, XPS, experiments. In parallel, we perform Hartree-Fock, HF, calculations of the binding energies, BEs, of the C1s electrons in a model molecule composed of the two constituents of the poly-epoxy sample. These C1s BEs were determined using the HF ΔSCF method, which is known to yield accurate values, especially for the shifts of the BEs, ΔBEs. We demonstrate the benefits of combining rigorous theory with careful XPS measurements in order to obtain correct assignments of the C1s XPS spectra of the polymer sample. Both the relative binding energies—by the ΔSCF method—and relative intensities—in the sudden approximation, SA, are calculated. It results in an excellent match with the experimental spectra. We are able to identify 9 different chemical environments under the C1s peak, where an exclusively experimental work would have found only 3 contributions. In addition, we observe that some contributions are localized at discrete binding energies, whereas others allow a much wider range because of the variation of their second neighbor bound polarization. Therefore, HF-ΔSCF simulations significantly increase the spectral resolution of XPS and thus offer a new avenue for the exploration of the surface of polymers.
ISSN 00219606
Educational Use Research
Learning Resource Type Article
Publisher Date 2016-08-21
Publisher Place United States
Journal Journal of Chemical Physics
Volume Number 145
Issue Number 7


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